Optical Detection Device with Low Dark Current

Abstract

To provide a photo-detecting apparatus.SOLUTION: A photo-detecting apparatus includes: a carrier conducting layer having a first surface; an absorption region doped with a first dopant having a first conductivity type and a first peak doping concentration; and a first electrode and a second electrode both formed over the first surface of the carrier conducting layer. The carrier conducting layer is doped with a second dopant having a second conductivity type and a second peak doping concentration, the carrier conducting layer includes a material different from a material of the absorption region, and the carrier conducting layer is in contact with the absorption region to form at least one heterointerface. A ratio between the first peak doping concentration of the absorption region and the second peak doping concentration of the carrier conducting layer is equal to or greater than 10.SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims the benefit of U.S. Provisional Patent Application No. 62 / 892,551, filed on August 28, 2019; U.S. Provisional Patent Application No. 62 / 899,153, filed on September 12, 2019; U.S. Provisional Patent Application No. 62 / 929,089, filed on October 31, 2019; and U.S. Provisional Patent Application No. 63 / 053,723, filed on July 20, 2020, each of which is hereby incorporated by reference in its entirety.

Background Art

[0002] A photodetector can be used to detect an optical signal and convert the optical signal into an electrical signal that can be further processed by other circuits. Photodetectors can be used in consumer electronics, image sensors, high - speed optical receivers, data communication, direct / indirect time - of - flight (TOF) ranging or imaging sensors, medical devices, and many other suitable applications.

Summary of the Invention

Means for Solving the Problems

[0003] This disclosure generally relates to a photodetection device and an image system including the photodetection device.

[0004] According to another embodiment of the present disclosure, a photodetection device is provided. The photodetection device includes an absorption region including a first dopant having a first peak doping concentration and a substrate supporting the absorption region. The substrate includes a second dopant having a second peak doping concentration that is less than the first peak doping concentration, and the absorption region includes a material different from the material of the substrate.

[0005] According to an embodiment of the present disclosure, a photodetection device is provided. The photodetection device includes a photodetection device, and the photodetection device includes a carrier conduction layer having a first surface and a second surface, and an absorption region that is in contact with the carrier conduction layer, receives an optical signal, and is configured to generate optical carriers in response to the optical signal. The absorption region is doped with a first dopant having a first conductivity type and a first peak doping concentration, the carrier conduction layer is doped with a second dopant having a second conductivity type and a second peak doping concentration, the carrier conduction layer includes a material different from the material of the absorption region, the carrier conduction layer is in contact with the absorption region to form at least one heterointerface, and a ratio between the doping concentration of the absorption region and the doping concentration of the carrier conduction region at at least one heterointerface is 10 or more. The photodetection device includes the absorption region and a first electrode and a second electrode formed on the same side of the carrier conduction layer.

[0006] According to an embodiment of the present disclosure, a photodetection device is provided. The photodetection device includes a photodetection device, and the photodetection device includes a carrier conduction layer having a first surface and a second surface, and an absorption region that is in contact with the carrier conduction layer, receives an optical signal, and is configured to generate optical carriers in response to the optical signal. The absorption region is doped with a first dopant having a first conductivity type and a first peak doping concentration, the carrier conduction layer is doped with a second dopant having a second conductivity type and a second peak doping concentration, the carrier conduction layer includes a material different from the material of the absorption region, the carrier conduction layer is in contact with the absorption region to form at least one heterointerface, and a ratio between the doping concentration of the absorption region and the doping concentration of the carrier conduction region at at least one heterointerface is 10 or more, or a ratio between the first peak doping concentration of the absorption region and the second peak doping concentration of the carrier conduction region is 10 or more. The photodetection device includes the absorption region and, in the carrier conduction layer, a second doped region that is in contact with the absorption region, has the same conductivity type as the first conductivity type, and is doped with a fourth dopant having a fourth peak doping concentration higher than the first peak doping concentration.

[0007] According to an embodiment of the present disclosure, an optical detection device is provided. The optical detection device includes an optical detection device, and the optical detection device includes a carrier conduction layer having a first surface and a second surface, and an absorption region that is in contact with the carrier conduction layer, receives an optical signal, and is configured to generate optical carriers in response to the optical signal. The absorption region is doped with a first dopant having a first conductivity type and a first peak doping concentration, the carrier conduction layer is doped with a second dopant having a second conductivity type and a second peak doping concentration, the carrier conduction layer includes a material different from the material of the absorption region, the carrier conduction layer is in contact with the absorption region to form at least one heterointerface, and the ratio between the doping concentration of the absorption region and the doping concentration of the carrier conduction region at at least one heterointerface is 10 or more, and the ratio between the first peak doping concentration of the absorption region and the second peak doping concentration of the carrier conduction region is 10 or more. At least 50% of the absorption region is doped with a doping concentration of the first dopant of 1×10 16 cm -3 or higher.

[0008] According to an embodiment of the present disclosure, an optical detection device is provided. The optical detection device includes an optical detection device, and the optical detection device includes a carrier conduction layer having a first surface and a second surface, and an absorption region that is in contact with the carrier conduction layer, receives an optical signal, and is configured to generate optical carriers in response to the optical signal. The absorption region is doped with a first dopant having a first conductivity type and a first peak doping concentration. The carrier conduction layer is doped with a second dopant having a second conductivity type and a second peak doping concentration. The carrier conduction layer includes a material different from the material of the absorption region. The carrier conduction layer is in contact with the absorption region to form at least one heterointerface. A ratio between the first peak doping concentration of the absorption region and the second peak doping concentration of the carrier conduction region is 10 or more. The optical detection device further includes a first electrode formed on the first surface of the carrier conduction layer, electrically coupled to the carrier conduction layer, separated from the absorption region, and configured to collect a part of the optical carriers, and a second electrode formed on the first surface of the carrier conduction layer, electrically coupled to the absorption region.

[0009] According to other embodiments of the present disclosure, a photodetection device is provided. The photodetection device includes a photodetection device, and the photodetection device includes a substrate having a first surface and a second surface, and on the first surface of the substrate, an absorption region configured to receive an optical signal and generate optical carriers in response to the optical signal, the absorption region being doped with a first dopant having a first conductivity type and a first peak doping concentration, the substrate being doped with a second dopant having a second conductivity type and a second peak doping concentration, the substrate including a material different from that of the absorption region, the substrate being in contact with the absorption region to form at least one heterointerface, and a ratio between the first peak doping concentration of the absorption region and the second peak doping concentration of the substrate being 10 or more, or a ratio between the doping concentration of the absorption region and the doping concentration of the substrate at at least one heterointerface being 10 or more; an absorption region; a first electrode formed on the first surface of the substrate and electrically coupled to the substrate, the first electrode being separated from the absorption region and configured to collect a portion of the optical carriers; and a second electrode formed on the first surface of the substrate and electrically coupled to the absorption region. According to other embodiments of the present disclosure, a photodetection device is provided.The photodetection device includes a photodetection device, and the photodetection device is an absorption region configured to receive an optical signal and generate optical carriers in response to the optical signal. The absorption region is doped with a first dopant having a first conductivity type and a first peak doping concentration. The absorption region, and on the absorption region, there is a protective layer having a first surface and a second surface facing the first surface. The protective layer is doped with a second dopant having a second conductivity type and a second peak doping concentration. The protective layer includes a material different from that of the absorption region. The protective layer is in contact with the absorption region to form at least one heterointerface. The ratio between the first peak doping concentration of the absorption region and the second peak doping concentration of the protective layer is 10 or more, or the ratio between the doping concentration of the absorption region and the doping concentration of the protective layer at at least one heterointerface is 10 or more. The protective layer, a first electrode formed on the first surface of the protective layer and electrically coupled to the protective layer, the first electrode being separated from the absorption region and configured to collect a part of the optical carriers, the first electrode, and a second electrode formed on the first surface of the protective layer and electrically coupled to the absorption region.

[0010] According to other embodiments of the present disclosure, a photodetection device is provided. The photodetection device includes a photodetection device, the photodetection device includes a carrier conduction layer having a first surface and a second surface, and an absorption region that is in contact with the carrier conduction layer and is configured to receive an optical signal and generate optical carriers in response to the optical signal. The absorption region is doped with a first dopant having a first conductivity type and a first peak doping concentration. The carrier conduction layer is doped with a second dopant having a second conductivity type and a second peak doping concentration. The carrier conduction layer includes a material different from the material of the absorption region. The carrier conduction layer is in contact with the absorption region to form at least one heterointerface. The ratio between the doping concentration of the absorption region and the doping concentration of the carrier conduction layer at at least one heterointerface is 10 or more, or the ratio between the first peak doping concentration of the absorption region and the second peak doping concentration of the carrier conduction layer is 10 or more. An absorption region, one or more switches electrically coupled to the absorption region and partially formed in the carrier conduction layer, each of the one or more switches includes a control electrode and a readout electrode formed on the first surface and separated from the absorption region, one or more switches, and an electrode formed on the first surface and electrically coupled to the absorption region.

[0011] According to another embodiment of the present disclosure, an optical detection device is provided. The optical detection device includes an optical detection device, and the optical detection device includes a carrier conduction layer having a first surface and a second surface, and an absorption region that is in contact with the carrier conduction layer and is configured to receive an optical signal and generate optical carriers in response to the optical signal. The absorption region is doped with a first dopant having a first conductivity type and a first peak doping concentration, the carrier conduction layer is doped with a second dopant having a second conductivity type and a second peak doping concentration, the carrier conduction layer includes a material different from the material of the absorption region, the carrier conduction layer is in contact with the absorption region to form at least one heterointerface, and the ratio between the doping concentration of the absorption region and the doping concentration of the carrier conduction layer at at least one heterointerface is 10 or more, or the ratio between the first peak doping concentration of the absorption region and the second peak doping concentration of the carrier conduction layer is 10 or more. The absorption region is electrically coupled to the absorption region and includes one or more switches partially formed in the carrier conduction layer. Each of the one or more switches includes a control electrode and a readout electrode formed on the same side of the carrier conduction layer. In the carrier conduction layer, there is a second doped region in contact with the absorption region, which has the same conductivity type as the first conductivity type and is doped with a fourth dopant having a fourth peak doping concentration higher than the first peak doping concentration. The second doped region and an electrode electrically coupled to the second doped region are provided.

[0012] According to other embodiments of the present disclosure, a photodetection device is provided. The photodetection device includes a photodetection device, and the photodetection device includes a carrier conduction layer having a first surface and a second surface, and an absorption region that is in contact with the carrier conduction layer and is configured to receive an optical signal and generate optical carriers in response to the optical signal. The absorption region is doped with a first dopant having a first conduction type and a first peak doping concentration. The carrier conduction layer is doped with a second dopant having a second conduction type and a second peak doping concentration. The carrier conduction layer includes a material different from the material of the absorption region. The carrier conduction layer is in contact with the absorption region to form at least one heterointerface. The ratio between the doping concentration of the absorption region and the doping concentration of the carrier conduction layer at at least one heterointerface is 10 or more, or the ratio between the first peak doping concentration of the absorption region and the second peak doping concentration of the carrier conduction layer is 10 or more. The photodetection device includes the absorption region and one or more switches that are electrically coupled to the absorption region and are partially formed in the carrier conduction layer. The photodetection device further includes one or more reading circuits that are electrically connected to the respective switches, and the one or more reading circuits include a voltage control transistor between a transfer transistor and a capacitor.

[0013] According to other embodiments of the present disclosure, a photodetection device is provided. The photodetection device includes an absorption region doped with a first dopant having a first conduction type and a first peak doping concentration, and a carrier conduction layer in contact with the absorption region. The carrier conduction layer includes a conduction region doped with a second dopant having a second conduction type and a second peak doping concentration lower than the first peak doping concentration. The carrier conduction layer includes or consists of a material different from the material of the absorption region, and the conduction region has a depth of less than 5 μm.

[0014] According to other embodiments of the present disclosure, a photodetector is provided. The photodetector includes an absorption region doped with a first dopant having a first peak doping concentration, a first contact region having a conductivity type, a second contact region having a conductivity type different from that of the first contact region, a charge region having the same conductivity type as that of the first contact region and partially located between the first contact region and the second contact region, and a substrate supporting the absorption region. The substrate includes a second dopant having a second peak doping concentration smaller than the first peak doping concentration, and the absorption region includes a material different from that of the substrate.

[0015] According to other embodiments of the present disclosure, a photodetector is provided. The photodetector includes a substrate, an absorption region supported by the substrate and doped with a first dopant having a first conductivity type, a plurality of first contact regions each having a conductivity type different from the first conductivity type and formed on the substrate, a second doped region formed in the absorption region and having the same conductivity type as the first conductivity type, and a plurality of third contact regions each having the same conductivity type as the first conductivity type and formed on the substrate. The first contact regions are arranged along a first plane, and the third contact regions are arranged along a second plane different from the first plane. In an embodiment, a plurality of multiplication regions are formed between the plurality of third contact regions and the plurality of first contact regions.

[0016] According to other embodiments of the present disclosure, a photodetector is provided. The photodetector includes an absorption region, a first contact region having a conductivity type, a second contact region in the absorption region and having a conductivity type different from that of the first contact region, a charge region having the same conductivity type as that of the first contact region and closer to the second contact region than to the first contact region, and a substrate supporting the absorption region. The charge region and the first contact region are formed on the substrate. The photodetector further includes a correction element integrated with the substrate to correct a position where multiplication occurs in the substrate.

[0017] According to other embodiments of the present disclosure, a photodetection device is provided. The photodetection device includes a substrate, an absorption region supported by the substrate, a first contact region having a conductivity type and formed on the substrate, a second contact region formed in the absorption region and having a conductivity type different from that of the first contact region, and a charge region formed on the substrate and having the same conductivity type as the first contact region, and the depth of the charge region is smaller than the depth of the first contact region. In certain embodiments, the depth of the charge region is between the depth of the second contact region and the depth of the first contact region.

[0018] According to other embodiments of the present disclosure, a photodetection device is provided. The photodetection device includes a photodetection device, and the photodetection device includes a substrate having a first surface and a second surface, and an absorption region on the first surface of the substrate configured to receive an optical signal and generate optical carriers in response to the optical signal. The absorption region is doped with a first dopant having a first conductivity type and a first peak doping concentration, the substrate is doped with a second dopant having a second conductivity type and a second peak doping concentration, the substrate includes a material different from the material of the absorption region, the substrate is in contact with the absorption region to form at least one heterointerface, and the ratio between the doping concentration of the absorption region and the doping concentration of the substrate at the at least one heterointerface is 10 or more, or the ratio between the first peak doping concentration of the absorption region and the second peak doping concentration of the substrate is 10 or more. The substrate further includes a waveguide configured to guide and confine an optical signal propagating through a defined region of the substrate to couple the optical signal to the absorption region.

[0019] According to other embodiments of the present disclosure, a photodetection device is provided. The photodetection device includes a photodetection device, and the photodetection device includes a carrier conduction layer having a first surface and a second surface, and an absorption region that is in contact with the carrier conduction layer, receives an optical signal, and is configured to generate optical carriers in response to the optical signal. The absorption region is doped with a first dopant having a first conductivity type and a first peak doping concentration, the carrier conduction layer is doped with a second dopant having a second conductivity type and a second peak doping concentration, the carrier conduction layer includes a material different from the material of the absorption region, the carrier conduction layer is in contact with the absorption region to form at least one heterointerface, and the ratio between the doping concentration of the absorption region and the doping concentration of the carrier conduction layer at at least one heterointerface is 10 or more. The photodetection device further includes an absorption region and N switches that are electrically coupled to the absorption region and are partially formed in the carrier conduction layer. The Y control signals are different from each other and are electrically coupled to the photodetection device, where Y ≤ N and Y is a positive integer. Each of the control signals controls one or more of the switches of the photodetection device.

[0020] According to other embodiments of the present disclosure, a photodetection device is provided. The photodetection device includes an absorption region including a first dopant having a first peak doping concentration and a substrate supporting the absorption region. The substrate includes a second dopant having a second peak doping concentration lower than the first peak doping concentration. The absorption region includes a material having a bandgap smaller than the bandgap of the material of the substrate. An embedded electric field region crosses the interface between the substrate and the absorption region, and a first width of the embedded electric field region in the substrate is greater than a second width of the embedded electric field region in the absorption region such that dark current is mostly generated from the substrate.

[0021] According to another embodiment of the present disclosure, an optical detection device is provided. The optical detection device includes an absorption region configured to receive an optical signal and generate optical carriers having a first polarity and a second polarity, a lightly doped region configured to receive a portion of the optical carriers having the first polarity from the absorption region, and a gain component configured to receive a portion of the optical carriers having the first polarity from the lightly doped region and generate an electrical signal having the second polarity. The number of charges of the electrical signal having the second polarity generated by the gain component is greater than the number of charges of the optical carriers generated by the absorption region.

[0022] According to another embodiment of the present disclosure, an optical detection device is provided. The optical detection device includes an absorption region doped with a first dopant type having a first peak doping concentration and configured to receive an optical signal and generate optical carriers having a first polarity and a second polarity, a lightly doped region doped with a second dopant type having a second peak doping concentration and configured to receive a portion of the optical carriers having the first polarity from the absorption region, where the first dopant type is different from the second dopant type, and a gain component configured to receive a portion of the optical carriers having the first polarity from the lightly doped region and generate an electrical signal having the second polarity. The ratio of the first peak doping concentration of the absorption region to the second peak doping concentration of the lightly doped region is 10 or more, and the number of charges of the electrical signal having the second polarity generated by the gain component is greater than the number of charges of the optical carriers generated by the absorption region.

[0023] According to other embodiments of the present disclosure, a method for amplifying an optical carrier received by a photodetector having a gain component is provided. The method includes receiving an optical signal in an absorption region to generate an optical carrier having a first type and an optical carrier having a second type, steering the optical carrier of the first type into a gain region, and generating an amplified electrical signal having the second type, the step of generating the amplified electrical signal including applying a first voltage to an emitter electrode of the gain component, and applying a second voltage to a collector electrode of the gain component such that a forward bias is created across a pn junction between an emitter region of the gain component and a lightly doped region of the gain component, and a reverse bias is created across a pn junction between a collector region of the gain component and the lightly doped region of the gain component, receiving a carrier of the first type in the lightly doped region of the gain component to increase the forward bias between the emitter region and the lightly doped region, and collecting, as the amplified electrical signal, a carrier of the second type emitted from the emitter region by the collector region.

[0024] According to other embodiments of the present disclosure, a photodetector is provided. The photodetector includes an absorption region configured to receive an optical signal and generate an optical carrier having a first polarity and a second polarity, a substrate configured to receive a portion of the optical carrier having the first polarity from the absorption region, and one or more switches electrically coupled to the absorption region and at least partially formed on the substrate, each of the switches including a gain component configured to receive a portion of the optical carrier having the first polarity and generate an electrical signal having the second polarity, the number of charges of the electrical signal having the second polarity generated by the gain component being greater than the number of charges of the optical carrier generated by the absorption region.

[0025] According to an embodiment of the present disclosure, an imaging system is provided. The imaging system includes a transmission unit capable of emitting light rays and a reception unit including an image sensor including a light detection device.

[0026] These and other objects of the present disclosure will become clearly apparent to those skilled in the art after reading the following detailed description of the preferred embodiments shown in various figures and drawings.

[0027] Many of the foregoing aspects, as well as the attendant advantages of this application, will be better understood and more readily appreciated when taken in conjunction with the accompanying drawings and reference is made to the following detailed description, which is to be read with a view to better understanding such aspects and advantages.

Brief Description of the Drawings

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Embodiments for Carrying Out the Invention

[0029] As used herein, terms such as "first", "second", "third", "fourth", and "fifth" describe various elements, components, regions, layers, and / or sections, and these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms may only be used to distinguish one element, component, region, layer, or section from another. Terms such as "first", "second", "third", "fourth", and "fifth", when used herein, do not include an order or sequence meaning unless clearly indicated by the context. Terms such as "light detection", "light sensing", "light ray detection", "light ray sensing", and any other similar terms can be used interchangeably with each other.

[0030] Spatial descriptions such as "above", "upper", and "lower" are indicated in relation to the orientation shown in the figures unless otherwise specified. It should be understood that the spatial descriptions used herein are for illustrative purposes only and that the practical implementation of the structures described herein can be spatially arranged in any orientation or manner on the premise that such an arrangement does not go against the advantages of the embodiments of the present disclosure.

[0031] As used herein, the term "intrinsic" means that the semiconductor material has no intentionally added dopants.

[0032] FIG. 1A shows a cross-sectional view of a photodetection device 100a according to an embodiment. The photodetection device 100a includes an absorption region 10 and a substrate 20 that supports the absorption region 10. In some embodiments, the absorption region 10 is entirely embedded in the substrate 20. In some embodiments, the absorption region 10 is partially embedded in the substrate 20. In some embodiments, the photodetection device 100a includes at least one heterointerface between the absorption region 10 and a carrier conduction layer that includes or consists of a material different from that of the absorption region 10. In some embodiments, the carrier conduction layer is the substrate 20. For example, in some embodiments, the substrate 20 includes a first surface 21 and a second surface 22 that faces the first surface 21. In some embodiments, the absorption region 10 includes a first surface 11, a second surface 12, and one or more side surfaces 13. The second surface 12 is between the first surface 11 of the absorption region 10 and the second surface 22 of the substrate 20. The side surfaces 13 are between the first surface 11 of the absorption region 10 and the second surface 12 of the absorption region 10. At least one of the first surface 11, the second surface 12, and the side surfaces 13 of the absorption region 10 is at least partially in direct contact with the substrate 20, and thus, the heterointerface is formed between the absorption region 10 and the substrate 20.

[0033] In some embodiments, the absorption region 10 is doped with a conduction type and includes a first dopant having a first peak doping concentration. In some embodiments, the absorption region 10 is configured to convert an optical signal, such as an incident light beam, into an electrical signal. In some embodiments, the optical signal enters the absorption region 10 from the first surface 21 of the substrate 20. In some embodiments, the optical signal enters the absorption region 10 from the second surface 22 of the substrate 20. In some embodiments, the absorption region 10 includes an absorption region AR defined by a light shielding body (not shown) that includes an optical window. The absorption region AR is a virtual region that receives the optical signal entering through the optical window.

[0034] In one embodiment, the carrier conduction layer, which is the substrate 20 in one embodiment, is doped with a conductivity type and includes a second dopant having a second peak doping concentration lower than the first peak doping concentration to reduce the dark current of the photodetector device 100a, which can improve the signal-to-noise ratio, sensitivity, and dynamic range characteristics of the photodetector device 100a.

[0035] In one embodiment, the first peak doping concentration is 1×10 16 cm -3 or higher. In one embodiment, the first peak doping concentration can be between 1×10 16 cm -3 and 1×10 20 cm -3 In one embodiment, the first peak doping concentration can be between 1×10 17 cm -3 and 1×10 20 cm -3 In one embodiment, the ratio of the first peak doping concentration to the second peak doping concentration is 10 or more so that the photodetector device 100a can further achieve a low dark current. In one embodiment, the ratio of the first peak doping concentration to the second peak doping concentration is 100 or more so that the photodetector device 100a can further achieve both a low dark current and a high quantum efficiency. In one embodiment, the conductivity type of the substrate 20 is p-type or n-type. In one embodiment, when the conductivity type of the substrate 20 is p-type using, for example, boron (B) and / or gallium (Ga) as dopants, the second peak doping concentration is 1×10 12 cm -3 and 1×10 16 cm -3 so that the photodetector device 100a can achieve both a low dark current and a high quantum efficiency. In one embodiment, when the conductivity type of the substrate 20 is n-type using, for example, phosphorus (P) and / or arsenic (As) as dopants, the second peak doping concentration is 1×10 14 cm-3 and 1×10 18 cm -3 and can be between them.

[0036] In some embodiments, in some embodiments, when the conductivity type of the carrier conduction layer, which is the substrate 20, has a second peak doping concentration of the substrate 20 lower than the first peak doping concentration of the absorption region 10, and thus is different from the conductivity type of the absorption region 10, a depletion region crosses the heterointerface between the substrate 20 and the absorption region 10. When the photodetector device is operating, the major portion of the depletion region is in the substrate 20. In other words, a first width of the depletion region in the substrate 20 is greater than a second width of the depletion region in the absorption region 10. In some embodiments, the ratio of the first width to the second width is greater than 10. In some embodiments, an embedded electric field region crosses the heterointerface between the substrate 20 and the absorption region 10, and a first width of the embedded electric field region in the substrate 20 is greater than a second width of the embedded electric field region in the absorption region 10 so that the dark current is generated mostly from the substrate 20. Therefore, the photodetector device can achieve a lower dark current. In some embodiments, the bandgap of the carrier conduction layer, which is the substrate 20, is greater than the bandgap of the absorption region 10.

[0037] In some embodiments, by having a second peak doping concentration of the substrate 20 lower than the first peak doping concentration of the absorption region 10, when the substrate 20 is of p-type and the absorption region 10 is of p-type, for example, in some embodiments, when the conductivity type of the carrier conduction layer, which is the substrate 20, is the same as the conductivity type of the absorption region 10, an electric field across the absorption region 10 can be reduced, and by extension, an electric field across the substrate 20 can be increased. That is, there is a difference between the electric field across the absorption region 10 and the electric field across the substrate 20. As a result, the dark current of the photodetector device is further reduced. In some embodiments, the bandgap of the carrier conduction layer, which is the substrate 20, is greater than the bandgap of the absorption region 10.

[0038] In one embodiment, the carrier conduction layer, which is the substrate 20, includes a first doped region 102 separated from the absorption region 10. The first doped region 102 is doped with a conduction type and contains a third dopant having a third peak doping concentration. The conduction type of the first doped region 102 is different from that of the absorption region 10. In one embodiment, the third peak doping concentration is higher than the second peak doping concentration. In one embodiment, the third peak doping concentration of the first doped region 102 is 1×10 18 cm -3 to 5×10 20 cm -3 and can be in between.

[0039] In one embodiment, at least 50% of the absorption region 10 is doped with a doping concentration of the first dopant of 1×10 16 cm -3 or more. In other words, at least half of the absorption region 10 is intentionally doped with the first dopant having a doping concentration of 1×10 16 cm -3 or more. For example, the ratio of the depth of the doping region in the absorption region 10 to the thickness of the absorption region 10 is 1 / 2 or more. In one embodiment, at least 80% of the absorption region 10 is intentionally doped with the first dopant having a doping concentration of 1×10 16 cm -3 or more in order to further reduce the dark current of the photodetector device. For example, the ratio of the depth of the doping region in the absorption region 10 to the thickness of the absorption region 10 is 4 / 5 or more.

[0040] In one embodiment, the carrier conduction layer can be significantly doped with a second dopant. For example, in one embodiment, at least 50% of the carrier conduction layer, which is the substrate 20, has a doping concentration of the second dopant of 1×10 12 cm -3 or more. In other words, at least half of the carrier conduction layer has a doping concentration of 1×10 12 cm -3It is intentionally doped with a second dopant having the above doping concentration. For example, the ratio of the depth of the doping region in the substrate 20 to the thickness of the substrate 20 is 1 / 2 or more. In one embodiment, at least 80% of the carrier conduction layer is 1×10 12 cm -3 or more and is intentionally doped with a second dopant having the above doping concentration. For example, the ratio of the depth of the doping region in the substrate 20 to the thickness of the substrate 20 is 4 / 5 or more.

[0041] In one embodiment, the carrier conduction layer can be locally doped with the second dopant. For example, in one embodiment, the carrier conduction layer, which is the substrate 20, includes a conduction region 201. At least a part of the conduction region 201 is between the first doping region 102 and the absorption region 10. In one embodiment, the conduction region 201 is partially overlapped with the absorption region 10 and the first doping region 102 in order to limit the path of carriers generated from the absorption region 10 and moving toward the first doping region 102. In one embodiment, the conduction region 201 has a depth measured from the first surface 21 of the substrate 20 along a direction D1 substantially perpendicular to the first surface 21 of the substrate 20. The depth is up to a position where a specific concentration such as a concentration between 1×10 14 cm -3 and 1×10 15 cm -3 is reached. In one embodiment, the depth of the conduction region 201 is less than 5 μm in order to transport carriers more efficiently. In one embodiment, the conduction region 201 may be overlapped with the entire first doping region 102. In one embodiment, the conduction region 201 has a width larger than the width of the absorption region 10.

[0042] In one embodiment, the first dopant is different from the second dopant. For example, the first dopant is boron and the second dopant is phosphorus. In one embodiment, the doping concentration of the first dopant at the heterointerface between the absorption region 10 and the carrier conduction layer, which is the substrate 20 in one embodiment, is 1×10 16 cm -3The above is the case. In certain embodiments, the doping concentration of the first dopant at the heterointerface is 1×10 16 cm -3 to 1×10 20 cm -3 or between 1×10 17 cm -3 and 1×10 20 cm -3 It may be between. In certain embodiments, the doping concentration of the second dopant at the heterointerface is lower than the doping concentration of the first dopant at the heterointerface. In certain embodiments, the doping concentration of the second dopant at the heterointerface is 1×10 12 cm -3 to 1×10 17 cm -3 between.

[0043] In certain embodiments, since the doping concentration of the first dopant at the heterointerface is sufficiently high, the dark current of the interface generated at the heterointerface can be reduced. As a result, the recombination rate of the interface can be reduced, and thus, the dark current at the heterointerface can be lower. In certain embodiments, since the doping concentration of the second dopant at the heterointerface is lower than the doping concentration of the first dopant at the heterointerface, the bulk dark current generated in the absorption region 10 is also reduced. In certain embodiments, the photodetector device 100a may have a recombination rate of the interface lower than 10 4 cm / s.

[0044] In certain embodiments, the ratio of the doping concentration of the first dopant to the doping concentration of the second dopant at the heterointerface is 10 or more so that the photodetector device 100a can achieve both a low dark current and a high quantum efficiency at the heterointerface. In certain embodiments, the ratio of the doping concentration of the first dopant to the doping concentration of the second dopant at the heterointerface is 100 or more so that the photodetector device 100a can exhibit both a further low dark current and a high quantum efficiency at the heterointerface.

[0045] In some embodiments, the second dopant may be in the absorption region 10, but may be present outside the absorption region 10 due to, for example, thermal diffusion or implantation residues. In some embodiments, the first dopant may be in the carrier conduction layer, which is the substrate 20 in some embodiments, but may be present outside the substrate region 20 due to, for example, thermal diffusion or implantation residues.

[0046] In some embodiments, the first dopant may be introduced into the absorption region 10 by any suitable process, such as in-situ growth, ion implantation, and / or thermal diffusion.

[0047] In some embodiments, the second dopant may be introduced into the substrate 20 by any suitable process, such as in-situ growth, ion implantation, and / or thermal diffusion.

[0048] In some embodiments, the absorption region 10 is made of a first material or a composite material of the first material. In some embodiments, the carrier conduction layer, which is the substrate 20, is made of a second material or a composite material of the second material. The second material or the composite material of the second material is different from the first material or the composite material of the first material. For example, in some embodiments, the combination of elements in the second material or the composite material of the second material is different from the combination of elements in the first material or the composite material of the first material.

[0049] In some embodiments, the bandgap of the carrier conduction layer, which is the substrate 20 in some embodiments, is larger than the bandgap of the absorption region 10. In some embodiments, the absorption region 10 comprises or consists of a semiconductor material. In some embodiments, the substrate 20 comprises or consists of a semiconductor material. In some embodiments, the absorption region 10 comprises or consists of a group III-V semiconductor material. In some embodiments, the substrate 20 comprises or consists of a group III-V semiconductor material. The group III-V semiconductor material may include, but is not limited to, GaAs / AlAs, InP / InGaAs, GaSb / InAs, or InSb. For example, in some embodiments, the absorption region 10 comprises or consists of InGaAs, and the substrate 20 comprises or consists of InP. In some embodiments, the absorption region 10 comprises or consists of a semiconductor material containing a group IV element. For example, Ge, Si, or Sn. In some embodiments, the absorption region 10 comprises Si x Ge y Sn 1-x-y and comprises or consists of Si x Ge y Sn 1-x-y where 0≦x≦1, 0≦y≦1, and 0≦x + y≦1. In some embodiments, the absorption region 10 comprises Ge 1-a Sn a and comprises or consists of Ge 1-a Sn a where 0≦a≦0.1. In some embodiments, the absorption region 10 comprises Ge x Si 1-x and comprises or consists of Ge x Si 1-x where 0≦x≦1. In some embodiments, the absorption region 10 made of intrinsic germanium is p-type due to material defects formed during the formation of the absorption region, where the defect density is 1×10 14 cm -3 to 1×10 16 cm -3That's all. In certain embodiments, the carrier conduction layer, which is the substrate 20 in certain embodiments, comprises or consists of a semiconductor material containing a Group IV element. For example, it is Ge, Si, or Sn. In certain embodiments, the substrate 20 comprises Si x Ge y Sn 1-x-y and contains Si x Ge y Sn 1-x-y or consists of them, where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, and 0 ≤ x + y ≤ 1. In certain embodiments, the substrate 20 comprises Ge 1-a Sn a and contains Ge 1-a Sn a or consists of them, where 0 ≤ a ≤ 0.1. In certain embodiments, the substrate 20 comprises Ge x Si 1-x and contains Ge x Sn 1-x or consists of them, where 0 ≤ x ≤ 1. In certain embodiments, the substrate 20 made of intrinsic germanium is p-type due to material defects formed during the formation of the absorption region, where the defect density is from 1×10 14 cm -3 to 1×10 16 cm -3 For example, in certain embodiments, the absorption region 10 contains Ge or consists of Ge, and the substrate 20 contains Si or consists of Si.

[0050] In certain embodiments, the conduction type of the absorption region 10 is p-type. In certain embodiments, the first dopant is a Group III element. In certain embodiments, the conduction type of the substrate 20 is n-type, and the second dopant is a Group V element.

[0051] In one embodiment, the photodetector device includes a first electrode 30 electrically coupled to a first doped region 102. The first electrode 30 is separated from the absorption region 10. A resistive contact can be formed between the first electrode 30 and the first doped region 102 according to the material of the first electrode 30 and the third peak doping concentration of the first doped region 102. In one embodiment, the shortest distance d between the first electrode 30 and one of the side surfaces 13 of the absorption region can be between 0.1 μm and 20 μm. In one embodiment, the shortest distance d between the first electrode 30 and one of the side surfaces 13 of the absorption region can be between 0.1 μm and 5 μm. In one embodiment, the distance can be between 0.5 μm and 3 μm. When the distance d between the first electrode 30 and the side surface 13 is greater than 20 μm, the speed of the photodetector device 100a becomes smaller. When the distance d between the first electrode 30 and the side surface 13 is less than 0.1 μm, the dark current of the photodetector device can be increased.

[0052] In one embodiment, the photodetector device 100a includes a second doped region 108 near the first surface 11 of the absorption region 10 in the absorption region 10. The second doped region 108 is doped with the same conductivity type as the absorption region 10. In one embodiment, the second doped region 108 includes a fourth dopant having a fourth peak doping concentration higher than the first peak doping concentration. For example, the fourth peak doping concentration of the second doped region 108 can be between 1×10 18 cm -3 and 5×10 20 cm -3 . In one embodiment, the second doped region 108 is not disposed on the first doped region 102 along the direction D1.

[0053] In one embodiment, the photodetector device 100a further includes a second electrode 60 electrically coupled to the second doped region 108. A resistive contact can be formed between the second electrode 60 and the second doped region 108 according to the material of the second electrode 60 and the fourth peak doping concentration of the second doped region 108. The second electrode 60 is on the first surface 11 of the absorption region 10.

[0054] In one embodiment, the carrier conduction layer includes a first surface and a second surface opposite the first surface 21. Both the first electrode 30 and the second electrode 60 are disposed on the first surface of the carrier conduction layer. That is, the first electrode 30 and the second electrode 60 are disposed on the same side of the carrier conduction layer, which is the substrate 20 in one embodiment, and this is beneficial for subsequent back-end manufacturing processes.

[0055] The first doped region 102 and the second doped region 108 can be semiconductor contact regions. In one embodiment, depending on the circuit electrically coupled to the first doped region 102 and the second doped region 108, carriers of the first type collected by one of the first doped region 102 and the second doped region 108 can be further processed, and carriers of the second type collected by the other doped region can be removed. Therefore, the photodetector device can have improved reliability and quantum efficiency.

[0056] In some embodiments, the absorption region 10 is doped with a step doping profile. In some embodiments, the maximum concentration of the step doping profile is higher than the second peak doping concentration of the second dopant. In some embodiments, the minimum concentration of the step doping profile is higher than the second peak doping concentration of the second dopant. In some embodiments, the step doping profile can be stepwise from the first surface 11 of the absorption region 10 or from the second doped region 108 of the absorption region 10 to the second surface 12 of the absorption region 10. In some embodiments, the step doping profile can decrease / increase gradually or decrease / increase stepwise according to the direction of carrier movement. In some embodiments, the concentration of the step doping profile is gradually decreased / increased from the first surface 11 or from the second doped region 108 of the absorption region 10 to the second surface 12 of the absorption region 10 according to the direction of carrier movement. In some embodiments, the concentration of the step doping profile is gradually decreased / increased radially from the center of the first surface 11 or the second doped region 108 of the absorption region 10 to the second surface 12 and the side surface 13 of the absorption region 10 according to the direction of carrier movement. For example, when the absorption region 10 extends over the entire substrate 20 and the first doped region 102 is of n-type, carriers with the first type such as electrons move in the absorption region 10 substantially along the direction from the first surface 11 to the second surface 12, and the concentration of the step doping profile of the first dopant such as boron is gradually decreased from the first surface 11 or from the second doped region 108 of the absorption region 10 to the second surface 12 of the absorption region 10. In some embodiments, the concentration of the step doping profile is gradually decreased / increased laterally from the edge of the first surface 11 or from the second doped region 108 of the absorption region 10 to the side surface 13 of the absorption region 10 according to the direction of carrier movement.

[0057] In some embodiments, the dark current of the photodetector device is, for example, about pA or less, such as less than 1×10 -12 A.

[0058] Figure 1B shows a cross-sectional view of a photodetection device according to an embodiment. The photodetection device 100b in Figure 1B is the same as the photodetection device 100a in Figure 1A. The differences are described below.

[0059] The photodetection device 100b further includes another first doped region 104 on the substrate 20. The first doped region 104 is the same as the first doped region 102 as described in Figure 1A. The first doped region 104 is separated from the absorption region 10. At least a part of the conduction region 201 is also between the first doped region 104 and the absorption region 10. In an embodiment, the conduction region 201 is partially overlapped with the absorption region 10 and the first doped region 104 to limit the path of carriers of the first type generated from the absorption region 10 and moving towards the first doped region 104.

[0060] In an embodiment, the two first doped regions 104, 102 are separated from each other. In an embodiment, the two first doped regions 104, 102 can be a continuous region such as a ring. The photodetection device 100b further includes a third electrode 40 electrically coupled to the first doped region 104. In an embodiment, the first electrode 30 and the third electrode 40 can be electrically coupled to the same circuit.

[0061] In an embodiment, the dark current of the photodetection device 100b is, for example, about pA or less, such as less than 1×10 -12 A.

[0062] The photodetection device according to the comparative example has a structure substantially the same as the structure of the photodetection device 100b in Figure 1B. The difference is that in the photodetection device of the comparative example, the doping concentration of the absorption region 10 is less than or equal to the second peak doping concentration of the substrate 20, and the doping concentration of the second dopant at the heterointerface is greater than or equal to the doping concentration of the first dopant at the heterointerface.

[0063] The details of the photodetection device according to the comparative example and the photodetection device 100b are listed in Table 1 and Table 2.

[0064]

Table 1

[0065]

Table 2

[0066] Referring to Table 3, compared with the comparative example, since the first peak doping concentration in the absorption region 10 of the photodetection device 100b is higher than the second peak doping concentration of the substrate 20, the photodetection device 100b can have a lower dark current, for example, at least two times lower.

[0067]

Table 3

[0068] Another photodetection device according to the comparative example has a structure substantially the same as that of the photodetection device 100b in FIG. 1B. The difference is that in another photodetection device of the comparative example, the doping concentration of the absorption region 10 is less than or equal to the second peak doping concentration of the substrate 20, and the doping concentration of the second dopant at the heterointerface is greater than or equal to the doping concentration of the first dopant at the heterointerface. The details of another photodetection device according to the comparative example and the photodetection device 100b are listed in Table 4 and Table 5.

[0069]

Table 4

[0070]

Table 5

[0071] Referring to Table 6, compared with another comparative example, since the first peak doping concentration in the absorption region 10 in the photodetection device 100b is higher than the second peak doping concentration in the substrate 20, the photodetection device 100b can have a lower dark current, for example, at least 20 times lower.

[0072]

Table 6

[0073] FIG. 1C shows a cross-sectional view of a photodetection device according to an embodiment. The photodetection device 100c in FIG. 1C is the same as the photodetection device 100a in FIG. 1A. The differences are described below.

[0074] The substrate 20 includes a base portion 20a and an upper portion 20b supported by the base portion 20a. The upper portion 20b has a width smaller than the width of the base portion 20a. The absorption region 10 is supported by the upper portion 20b of the substrate 20. The conduction region 201 is in the upper portion 20b. The first doped region 102 is in the base portion 20a. The first doped region 102 has a width larger than the width of the upper portion 20b of the substrate 20, and thus a part of the first doped region 102 is not covered by the upper portion 20b. The second doped region 108 is disposed on the first doped region 102 along the direction D1, and the conduction region 201 is between the first doped region 102 and the second doped region 108. Carriers of the first type generated from the absorption region 10, such as electrons, move along the direction D1 through the conduction region 201 toward the first doped region 102.

[0075] In an embodiment, the first electrode 30 can be in any suitable shape, such as a ring from the top view of the photodetection device. In an embodiment, the photodetection device 100c includes two first electrodes 30 that are electrically coupled to the first doped region 102 and separated from each other. In an embodiment, the first electrode 30 is disposed on the opposite side of the absorption region 10.

[0076] In one embodiment, when impact ionization occurs based on the reverse bias voltages applied to the second doped region 108 and the first doped region 102, the photodetection device 100c can be an avalanche photodiode operated in a linear mode (reverse bias voltage < breakdown voltage) or a Geiger mode (reverse bias voltage > breakdown voltage), and a portion of the conduction region 201 between the absorption region 10 and the first doping region 102 can be a multiplication region. Therefore, the multiplication region can generate one or more additional charge carriers in response to receiving one or more carriers generated from the absorption region 10.

[0077] FIG. 1D shows a cross-sectional view of a photodetection device according to an embodiment. The photodetection device 100d in FIG. 1D is the same as the photodetection device 100c in FIG. 1C. The differences are described below.

[0078] The photodetection device 100d further includes a charge layer 202 in the upper portion 20b of the substrate 20. The charge layer 202 is in direct contact with the absorption region 10 or overlaps a portion of the absorption region 10. The charge layer 202 has the same conductivity type as the absorption region 10. For example, when the conductivity type of the absorption region 10 is p, the conductivity type of the charge layer 202 is p. The charge layer 202 has a peak doping concentration higher than the second peak doping concentration of the conduction region 201 and lower than the first peak doping concentration of the absorption region 10. In one embodiment, the charge layer 202 has a thickness between 10 nm and 500 nm. The charge layer can reduce the electric field across the absorption region 10, thereby increasing the electric field across the conduction region 201. That is, there is a difference between the electric field across the absorption region 10 and the electric field across the conduction region 201. As a result, the speed and responsiveness of the photodetection device 100d are also higher, and the dark current of the photodetection device 100d is also smaller.

[0079] Figure 2A shows a cross-sectional view of a photodetector device according to an embodiment. The photodetector device 200a in FIG. 2A is similar to the photodetector device 100a in FIG. 1A. The differences are described below. The second doped region 108 is in the substrate 20. In other words, the fourth peak doping concentration of the second doped region 108 is located in the substrate 20. In an embodiment, the second doped region 108 is below the first surface 21 of the substrate 20 and is in direct contact with the absorption region 10. For example, the second doped region 108 may be in contact with or overlap one of the side surfaces 13 of the absorption region 10. As a result, carriers generated from the absorption region 10 can move from the absorption region 10 through the heterointerface between the absorption region 10 and the substrate 20 towards the second doped region 108. The second electrode 60 is on the first surface 21 of the substrate 20.

[0080] By having the second doped region 108 in the substrate 20 instead of in the absorption region 10, both the second electrode 60 and the first electrode 30 can be formed above the first surface 21 of the substrate 20. Therefore, the height difference between the second electrode 60 and the first electrode 30 can be reduced, whereby the subsequent manufacturing process will benefit from this design. Additionally, the area of the absorption region 10 that absorbs the optical signal can be made larger.

[0081] Figure 2B shows a cross-sectional view of a photodetector device according to an embodiment. The photodetector device 200b in FIG. 2B is similar to the photodetector device 200a in FIG. 2A. The differences are described below. The second doped region 108 may also be in contact with or overlap the second surface 12 of the absorption region 10.

[0082] FIG. 2C shows a cross-sectional view of a photodetector device according to an embodiment. The photodetector device 200c in FIG. 2C is similar to the photodetector device 200b in FIG. 2B. The differences are described below. The absorption region 10 extends across the entire substrate 20. A part of the second doped region 108 is covered by the absorption region 10. In some embodiments, the width w2 of the second doped region 108 covered by the absorption region 10 can be greater than 0.2 μm. In some embodiments, the absorption region 10 has a width w1. The width w2 is 0.5w1 or less. With this design, two different types of carriers can move from the absorption region 10 to the first doped region 102 and from the absorption region 10 to the second doped region 108 without any hindrance, respectively.

[0083] FIG. 2D shows a cross-sectional view of a photodetector device according to an embodiment. The photodetector device 200d in FIG. 2D is similar to the photodetector device 200a in FIG. 2A. The differences are described below. The absorption region 10 is entirely embedded in the substrate 20. In some embodiments, the gradual doping profile of the first dopant is gradually reduced laterally from the side surface 13 near the second doped region 108 to the side surface 13 near the conduction region 201. FIG. 2E shows a schematic diagram of a photodetector device according to an embodiment. The photodetector device 200e includes a pixel (not labeled) and a column bus electrically coupled to the pixel. The pixel includes a photodetector device and a readout circuit (not labeled) electrically coupled to the photodetector device and the column bus. The photodetector device can be any of the photodetector devices in FIGS. 1A - 1D and FIGS. 2A - 2D, such as the photodetector device 100a in FIG. 1A. In some embodiments, the readout circuit (not labeled) and the column bus may be fabricated on another substrate and integrated / co-packaged with the photodetector device via die / waf er bonding or stacking. In some embodiments, the photodetector device 200e includes a bonding layer (not shown) between the readout circuit and the photodetector device. The bonding layer can include any suitable material, such as an oxide, semiconductor, metal, or alloy.

[0084] In one embodiment, the readout circuit can be electrically coupled to the first doped region 102 or the second doped region 108 to process the collected carriers associated with the first type, and a supply voltage or a ground voltage can be applied to the other doped region to remove the other carriers associated with the second type opposite to the first type.

[0085] For example, when the first doped region 102 is of the n-type and the second doped region 108 is of the p-type, the readout circuit can be electrically coupled to the first doped region 102 to process the electrons collected for further application, and the ground voltage can be applied to the second doped region 108 to remove holes. For other examples, the readout circuit may be electrically coupled to the second doped region 108 to process the holes collected for further processing, and the supply voltage may be applied to the first doped region 102 to remove electrons.

[0086] In one embodiment, the readout circuit can be a three-transistor configuration consisting of a reset gate, a source follower, and a select gate, a four-transistor configuration including an additional transfer gate, or any suitable circuit for processing the collected charge. For example, the readout circuit includes a transfer transistor 171A, a reset transistor 141A, a capacitor 150A coupled to the reset transistor 141A, a source follower 142A, and a row selection transistor 143A. Examples of the capacitor 150A include, but are not limited to, a floating diffusion capacitor, a metal-oxide-metal (MOM) capacitor, a metal-insulator-metal (MIM) capacitor, and a metal-oxide-semiconductor (MOS) capacitor.

[0087] The transfer transistor 171A transfers the carriers from the photodetector device 100a to the capacitor 150A. In other words, the transfer transistor 171A is configured to output a photocurrent IA1 in response to a switching signal TG1. When the switching signal TG1 turns on the transfer transistor 171A, the photocurrent IA1 is generated.

[0088] At the start, the reset signal RST resets the output voltage VOUT1 to VDD. Next, when the switching signal TG1 turns on the transfer transistor 171A, a photocurrent IA1 is generated, and the output voltage VOUT1 across the capacitor 150A decreases until the switching signal TG1 turns off the transistor 171A.

[0089] In another embodiment, the reading circuit may be fabricated on another substrate and may be integrated / co-packaged with the photodetection device 100a via die / waf er bonding or stacking.

[0090] In one embodiment, the photodetection device is a CMOS image sensor operable at a frame rate of 1000 frames per second (1000 fps) or less.

[0091] FIG. 2F shows a schematic diagram of the circuit of a photodetection device according to an embodiment. The photodetection device 200f is similar to the photodetection device 200e in FIG. 2E. The differences are described below.

[0092] The reading circuit of the photodetection device 200f further includes a voltage control transistor 130A between the transfer transistor 171A and the capacitor 150A. The voltage control transistor 130A is configured as a current buffer. Specifically, the output terminal of the voltage control transistor 130A is coupled to the input terminal of the capacitor 150A, the input terminal of the voltage control transistor 130A is coupled to the output terminal of the transistor 171A, and the control terminal of the voltage control transistor 130A is coupled to a control voltage VC1.

[0093] Since the voltage control transistor 130A is coupled between the transfer transistor 171A and the capacitor 150A, the output terminal of the transfer transistor 171A and the input terminal of the capacitor 150A are separated. When the voltage control transistor 130A is operated below the threshold or in the saturation region, the output terminal of the transfer transistor 171A can be controlled at a constant voltage VA1 or biased to reduce the dark current generated by the photodetection device 100a.

[0094] FIG. 3A shows a top view of a photodetection device according to an embodiment. FIG. 3B shows a cross-sectional view along line A-A' in FIG. 3A according to an embodiment. The photodetection device includes an absorption region 10 and a substrate 20 that supports the absorption region 10. The absorption region 10 is similar to the absorption region 10 as described in FIG. 1A. The substrate 20 is similar to the substrate 20 as described in FIG. 1A. The difference between the photodetection device 300a in FIG. 3A and the photodetection device 100a in FIG. 1A is described below. The photodetection device 300a is electrically coupled to the absorption region 10 and includes a first switch (not labeled) and a second switch (not labeled) that are partially formed in a carrier conduction layer that is the substrate 20 in one embodiment. The first switch includes a control region C1 that includes a control electrode 340a. The first switch further includes a readout electrode 330a separated from the control electrode 340a. The second switch includes a control region C2 that includes a control electrode 340b. The second switch further includes a readout electrode 330b separated from the control electrode 340b. In one embodiment, the readout electrodes 330a, 330b and the control electrodes 340a, 340b are formed on the first surface 21 of the substrate 20 and separated from the absorption region 10. In one embodiment, the readout electrode 330a and the readout electrode 330b are disposed on opposite sides of the absorption region 10. In one embodiment, the shortest distance between one of the control electrodes and one or more sides of the absorption region is between 0.1 μm and 20 μm.

[0095] In one embodiment, the light detection device includes pixels each including a light detection device 300a as described above, and the pixels further include two control signals, such as a first control signal and a second control signal, which control control regions C1 and C2, respectively, to control the moving direction of electrons or holes generated by the absorbed photons in the absorption region 10. In one embodiment, the first control signal is different from the second control signal. For example, when a voltage is used, if a bias is applied to one of the control signals with respect to the other control signal, an electric field is created between two portions immediately below the control electrodes 340a and 340b, similar to that in the absorption region 10, and free carriers in the absorption region 10 drift toward one of the portions immediately below the readout electrodes 330b and 330a according to the direction of the electric field. In one embodiment, the first control signal includes a first phase and the second control signal includes a second phase, where the first control phase does not overlap with the second control phase. In one embodiment, the first control signal is fixed at a voltage value V and the second control signal oscillates between voltage values V±ΔV. In one embodiment, ΔV is generated by a changing voltage signal, such as a sine wave signal, a clock signal, or a pulse signal, which operates, for example, between 0V and 3V. The direction of the bias value determines the drift direction of carriers generated from the absorption region 10. The control signal is a modulation signal.

[0096] In one embodiment, the first switch includes a first doped region 302a under the readout electrode 330a. The second switch includes a first doped region 302b under the readout electrode 330b. In one embodiment, the first doped regions 302a and 302b have a conductivity type different from that of the absorption region 10. In one embodiment, the first doped regions 302a and 302b include a dopant and a dopant profile with a peak dopant concentration. In one embodiment, the peak doping concentration of the first doped regions 302a and 302b is higher than a second peak doping concentration. In one embodiment, the peak dopant concentration of the first doped regions 302a and 302b depends on the materials of the readout electrodes 330a and 330b and the substrate 20, and is, for example, 5×1018 cm -3 and 5×10 20 cm -3 and may be between. The first doped regions 302a, 302b are carrier collection regions for collecting carriers of the first type generated from the absorption region 10 based on the control of two control signals.

[0097] In certain embodiments, absorption functions and carrier control functions, such as carrier demodulation and carrier collection, operate in the absorption region 10 and, in certain embodiments, the carrier conduction layer, which is the substrate 20, respectively.

[0098] In certain embodiments, the photodetector device 300a may include a second doped region 108 and a second electrode 60 that are respectively similar to the second doped region 108 and the second electrode 60 in FIG. 1A. The second doped region 108 is for removing carriers of a second type opposite to the first type that are not collected by the first doped regions 302a, 302b during the operation of the photodetector device. In certain embodiments, the control electrode 340a is symmetric with the control electrode 340b with respect to the axis passing through the second electrode 60. In certain embodiments, the readout electrode 330a is symmetric with the readout electrode 330b with respect to the axis passing through the second electrode 60. The control electrodes 340a, 340b, the readout electrodes 330a, 330b, and the second electrode 60 are all disposed on the first surface of the carrier conduction layer. That is, the control electrodes 340a, 340b, the readout electrodes 330a, 330b, and the second electrode 60 are on the same side of the carrier conduction layer, which is the substrate 20 in certain embodiments.

[0099] In one embodiment, the substrate 20 of the photodetection device 300a includes a conductive region 201 similar to the conductive region 201 as described in FIG. 1A. The differences are described below. In one embodiment, from the cross-sectional view of the photodetection device 300a, the width of the conductive region 201 can be greater than the distance between the two read electrodes 330a, 330b. In one embodiment, the conductive region 201 is overlapped with the entire first doped regions 302a, 302b. In one embodiment, the width of the conductive region 201 can be smaller than the distance between the two read electrodes 330a, 330b and can be greater than the distance between the two control electrodes 340a, 340b. In one embodiment, the conductive region 201 is overlapped with a part of the first doped region 302a and a part of the first doped region 302b. Since the conductive region 201 is overlapped with a part of the first doped region 302a and a part of the first doped region 302b, carriers of the first type generated from the absorption region 10 can be restricted to the conductive region 201 and can move toward one of the first doped regions 302a, 302b based on the control of two control signals. For example, when the first doped regions 302a, 302b are of n-type, the conductive region 201 is of n-type, the second doped region 108 is of p-type, electrons generated from the absorption region 10 are restricted in the conductive region 201, can move toward one of the first doped regions 302a, 302b based on the control of two control signals, holes can move toward the second doped region 108, and can be further removed by a circuit.

[0100] In one embodiment, the photodetection device includes a pixel array including a plurality of repeating pixels. In one embodiment, the pixel array can be a one-dimensional or two-dimensional array of pixels.

[0101] The photodetection device according to the comparative example has substantially the same structure as the structure of the photodetection device 300a in FIG. 3A. The difference is that in the photodetection device of the comparative example, the doping concentration of the absorption region 10 is equal to or lower than the second peak doping concentration of the substrate 20, and the doping concentration of the second dopant at the heterointerface is equal to or higher than the doping concentration of the first dopant at the heterointerface.

[0102] Details of the photodetection device according to the comparative example and the photodetection device 300a are listed in Tables 7 and 8.

[0103]

Table 7

[0104]

Table 8

[0105] Referring to Tables 9 and 10, compared with the comparative example, since the first peak doping concentration of the absorption region 10 in the photodetection device 300a is higher than the second peak doping concentration of the substrate 20, the photodetection device 300a can have a lower dark current, for example, at least 100 times lower.

[0106]

Table 9

[0107]

Table 10

[0108] In certain embodiments, a voltage can be applied to the second electrode 60. In certain embodiments, the voltage applied to the second electrode 60 can reduce the leakage current between the second doped region 108 and the control regions C1, C2. In certain embodiments, the voltage is between the voltage applied to the control electrode 340a and the voltage applied to the control electrode 340b when operating the photodetection device 300a.

[0109] FIG. 4A shows a top view of a photodetection device according to an embodiment. FIG. 4B shows a cross-sectional view along the line A-A' in FIG. 4A according to an embodiment. FIG. 4C shows a cross-sectional view along the line B-B' in FIG. 4A according to an embodiment. The photodetection device 400a in FIG. 4A is similar to the photodetection device 300a in FIG. 3A. The differences are described below.

[0110] Referring to FIGS. 4A and 4B, the second doped region 108 is in the substrate 20. In other words, the fourth peak doping concentration of the second doped region 108 is located in the substrate 20. The second doped region 108 is below the first surface 21 of the substrate 20 and is in direct contact with the absorption region 10. For example, the second doped region 108 may be in contact with or overlap one of the side surfaces 13 of the absorption region 10. As a result, carriers of the second type not collected by the first doped regions 302a, 302b can move from the absorption region 10 through the heterointerface between the absorption region 10 and the substrate 20 towards the second doped region 108.

[0111] For example, when the first doped regions 302a, 302b are of the n-type, the conduction region 201 is of the n-type, the second doped region 108 is of the p-type, electrons generated from the absorption region 10 are restricted in the conduction region 201 and can move towards one of the first doped regions 302a, 302b based on the control of two control signals, and holes can move towards the second doped region 108 through the heterointerface between the absorption region 10 and the substrate 20 and can be further removed by a circuit.

[0112] The second electrode 60 is on the first surface 21 of the substrate 20. By having a second doped region 108 in the substrate 20 instead of the absorption region 10, the second electrode 60, the readout electrodes 330a, 330b, and the control electrodes 340a, 340b can all be formed in the same plane above the first surface 21 of the substrate 20. Therefore, the height difference between the second electrode 60 and any two of the four electrodes 330a, 330b, 340a, 340b can be reduced, whereby the subsequent manufacturing process will benefit from this design. Additionally, the area of the absorption region 10 that absorbs optical signals can be made larger.

[0113] FIG. 5A shows a top view of a photodetector device according to an embodiment. FIG. 5B shows a cross-sectional view along line A-A' in FIG. 5A according to an embodiment. FIG. 5C shows a cross-sectional view along line B-B' in FIG. 5A according to an embodiment. The photodetector device 500a in FIG. 4A is similar to the photodetector device 400a in FIG. 4A. The differences are described below. The readout electrodes 330a, 330b and the control electrodes 340a, 340b are arranged on the same side of the absorption region 10, which improves the contrast ratio of the photodetector device 400a because carriers are moved out from the absorption region 10 through one of the side surfaces 13. In an embodiment, the distance between the readout electrodes 330a, 330b along the direction Y can be larger than the distance between the control electrodes 340a, 340b along the direction Y. In an embodiment, the distance between the readout electrodes 330a, 330b along the direction Y can be substantially the same as the distance between the control electrodes 340a, 340b along the direction Y.

[0114] FIG. 6A shows a top view of a photodetection device according to an embodiment. FIG. 6B shows a cross-sectional view along line A-A' in FIG. 6A according to an embodiment. The photodetection device 600a in FIG. 6A is similar to the photodetection device 500a in FIG. 5A. For example, the readout electrodes 330a, 330b and the control electrodes 340a, 340b are arranged on the same side of the absorption region 10. The differences are described below.

[0115] Referring to FIGS. 6A and 6B, a second doped region 108 is in the substrate 20. In other words, the fourth peak doping concentration of the second doped region 108 is located in the substrate 20. The second doped region 108 is below the first surface 21 of the substrate 20 and is in direct contact with the absorption region 10. For example, the second doped region 108 may be in contact with or overlap one of the side surfaces 13 of the absorption region 10. As a result, carriers of the second type not collected by the first doped regions 302a, 302b can move from the absorption region 10 through the heterointerface between the absorption region 10 and the substrate 20 towards the second doped region 108. The second electrode 60 is on the first surface 21 of the substrate 20. The absorption region 10 is between the second electrode 60 and the electrodes 330a, 330b, 340a, 340b.

[0116] By having the second doped region 108 in the substrate 20 instead of in the absorption region 10, the second electrode 60 and the four electrodes 330a, 330b, 340a, 340b can all be formed on the same plane above the first surface 21 of the substrate 20. Therefore, the height difference between any two of the second electrode 60 and the four electrodes 330a, 330b, 340a, 340b can be reduced, whereby the subsequent manufacturing process will benefit from this design. Additionally, the area of the absorption region 10 that absorbs the optical signal can be made larger.

[0117] In an embodiment, the conduction region 201 can overlap the entire first doped regions 302a, 302b.

[0118] FIG. 6C shows a top view of a photodetection device according to an embodiment. FIG. 6D shows a cross-sectional view along line A-A' in FIG. 6C according to an embodiment. FIG. 6E shows a cross-sectional view along line B-B' in FIG. 6C according to an embodiment. The photodetection device 600c in FIG. 6C is similar to the photodetection device 600a in FIG. 6A, and the differences are described below. The photodetection device 600c further includes a confinement region 180 between the absorption region 10 and the first doped regions 302a, 302b to cover at least a part of the heterointerface between the absorption region 10 and the substrate 20. The confinement region 180 has a conductivity type different from that of the first doped regions 302a, 302b. In one embodiment, the confinement region 180 includes a dopant having a peak doping concentration. The peak doping concentration is 1×10 16 cm -3 or more. The conduction region 201 has a passage 181 formed through the confinement region 180 so that a part of the conduction region 201 remains in direct contact with the absorption region 10 to move optical carriers from the absorption region 10 toward the first doped regions 302a, 302b. That is, the passage 181 is not covered by the confinement region 180. In one embodiment, the peak doping concentration of the confinement region 180 is lower than the second peak doping concentration of the conduction region 201. In one embodiment, the peak doping concentration of the confinement region 180 is higher than the second peak doping concentration of the conduction region 201. For example, when the photodetection device is configured to collect electrons, the confinement region 180 is of p-type and the first doped regions 302a, 302b are of n-type. After optical carriers are generated from the absorption region 10, holes are removed through the second doped region 108 and the second electrode 60, and electrons are confined by the confinement region 180 and move from the absorption region 10 through the passage 181 toward one of the first doped regions 302a, 302b instead of moving out from the entire heterointerface between the absorption region 10 and the substrate 20. Therefore, the photodetection device 600c can have improved demodulation contrast by including the confinement region 180 between the absorption region 10 and the first doped regions 302a, 302b.

[0119] Figure 6F shows a top view of a photodetector device according to an embodiment. The photodetector device 600f in FIG. 6F is the same as the photodetector device 600c in FIG. 6C. The difference is that, instead of moving out from the other side surface 13 of the absorption region 10, the confinement region 180 is extended to cover two other side surfaces 13 of the absorption region 10 in order to further confine carriers and allow them to pass through the passage 181 at one of the side surfaces 13 of the absorption region 10. In one embodiment, the peak doping concentration of the confinement region 180 is lower than the peak doping concentration of the second doped region 108. In one embodiment, the confinement region 180 and the second doped region 108 are formed by two different fabrication process steps, such as using different masks.

[0120] Figure 6G shows a top view of a photodetector device according to an embodiment. The photodetector device 600g in FIG. 6G is the same as the photodetector device 600f in FIG. 6F. The difference is that the second doped region 108 can function as the confinement region 180 described in FIG. 6F. In other words, the second doped region 108 can both remove carriers not collected by the first doped regions 302a, 302b and confine carriers collected from the absorption region 10, instead of moving them out from the other side surface 13 of the absorption region 10, towards one of the first doped regions 302a, 302b through the passage 181 at one of the side surfaces 13.

[0121] FIG. 7A shows a top view of a photodetector device according to an embodiment. FIG. 7B shows a cross-sectional view along line A-A' in FIG. 7A according to an embodiment. The photodetector device 700a is similar to the photodetector device 300a in FIG. 3A. The differences are described below. In an embodiment, the photodetector device includes N switches that are electrically coupled to the absorption region 10 and are partially formed on the substrate 20, where N is an integer greater than 3. For example, N can be 3, 4, 5, etc. In an embodiment, the pixels of the photodetector device further include Y different control signals from each other, where 3≤Y≤N, Y is a positive integer, and each of the control signals controls one or more of the control regions of the photodetector device 700a. In an embodiment, each of the control signals includes a phase, and the phase of one of the control signals does not overlap with the phases of the other control signals. Referring to FIGS. 7A and 7B, in an embodiment, the photodetector device 700a includes four switches (not labeled) that are electrically coupled to the absorption region 10 and are partially formed on the substrate 20. Each of the switches includes control regions C1, C2, C3, C4 that include control electrodes 340a, 340b, 340c, 340d. Each of the switches includes readout electrodes 330a, 330b, 330c, 330d that are separated from the control electrodes 340a, 340b, 340c, 340d. In an embodiment, the readout electrodes 330a, 330b, 330c, 330d and the control electrodes 340a, 340b, 340c, 340d are formed on the first surface 21 of the substrate 20 and are separated from the absorption region 10.

[0122] In an embodiment, the four switches are respectively disposed on four side surfaces 13.

[0123] In an embodiment, each of the switches includes a first doped region (not shown) under the readout electrodes 330a, 330b, 330c, 330d, and the first doped region is similar to the first doped regions 302a, 302b as described in FIG. 3A.

[0124] In one embodiment, the pixels of the photodetection device include four control signals for controlling control regions C1, C2, C3, and C4, respectively, so as to control the moving direction of electrons or holes generated by the absorption region 10. For example, when a voltage is used, a bias is applied to the control signal for controlling the control region C1 with respect to the other control signals, and an electric field is created between the four portions immediately below the control electrodes 340a, 340b, 340c, and 340d, similar to those in the absorption region 10. Free carriers in the absorption region 10 drift toward one of the first doped regions below the readout electrodes 330a, 330b, 330c, and 330d according to the direction of the electric field. In one embodiment, each of the control signals has a phase that does not overlap with the phases of the others.

[0125] In one embodiment, the conduction region 201 can be of any suitable shape, such as rectangular or square.

[0126] FIG. 7C shows a top view of a photodetection device according to an embodiment. The photodetection device 700c is similar to the photodetection device 700a in FIG. 7A. The differences are described below. The arrangement of the readout electrodes 330a, 330b, 330c, and 330d is different from the arrangement of the control electrodes 340a, 340b, 340c, and 340d. For example, four switches are respectively arranged at the four corners of the absorption region 10.

[0127] FIG. 7D shows a top view of a photodetector device according to an embodiment. The photodetector device 700d is similar to the photodetector device 700a in FIG. 7A. The differences are described below. The photodetector device 700d includes eight switches (not labeled) that are electrically coupled to the absorption region 10 and are partially formed on the substrate 20. Similarly, each of the switches includes a control region (not labeled) that includes control electrodes 340a, 340b, 340c, 340d, 340e, 340f, 340g, 340h, and includes readout electrodes 330a, 330b, 330c, 330d, 330e, 330f, 330g, 330h that are separated from the control electrodes 340a, 340b, 340c, 340d, 340e, 340f, 340g, 340h.

[0128] In one embodiment, the photodetector device includes a pixel that includes a photodetector device 700d as described above, and the pixel includes a plurality of control signals that are different from each other and control the multiple switches of the photodetector device 700d. That is, in the same pixel, the number of control signals is smaller than the number of switches. For example, the pixel can include two control signals that are different from each other, and each of the control signals controls two of the switches. For example, the control electrode 340a and the control electrode 340b can be electrically coupled to the same control signal and can be controlled by the same control signal. In one embodiment, the pixel can include a plurality of control signals that control each of the switches. That is, in the same pixel, the number of control signals is equal to the number of switches. For example, the pixels of the photodetector device include eight control signals that are different from each other and control each of the switches of the photodetector device 700d.

[0129] FIG. 7E shows a top view of a photodetection device according to an embodiment. The photodetection device 700e is similar to the photodetection device 700d in FIG. 7D. The differences are described below. The arrangement of the readout electrodes 330a, 330b, 330c, 330d, 330e, 330f, 330g, 330h is different from the arrangement of the control electrodes 340a, 340b, 340c, 340d, 340e, 340f, 340g, 340h. For example, every other one of the eight switches is arranged at each of the four corners of the absorption region 10. The conduction region 201 may be octagonal, although it is not limited thereto.

[0130] FIG. 8A shows a top view of a photodetector device according to an embodiment. FIG. 8B shows a cross-sectional view along line A-A' in FIG. 8A according to an embodiment. The photodetector device 800a in FIG. 8A is similar to the photodetector device 700a in FIG. 7A. The differences are described below. The second doped region 108 is in the substrate 20. In other words, the fourth peak doping concentration of the second doped region 108 is located in the substrate 20. In an embodiment, the second doped region 108 includes a plurality of small regions 108a, 108b, 108c, 108d that are separated from each other and in direct contact with the absorption region 10. For example, the small regions 108a, 108b, 108c, 108d can contact or overlap at least a part of the side surface 13 of the absorption region 10. As a result, carriers generated from the absorption region 10 and not collected by the first doped region can move from the absorption region 10 through the heterointerface between the absorption region 10 and the substrate 20 towards one or more of the small regions 108a, 108b, 108c, 108d. In an embodiment, in order to avoid preventing the path of the collected carriers from moving from the absorption region 10 towards one of the first doped regions, the small regions 108a, 108b, 108c, 108d are not between the absorption region 10 and the first doped region of any switch. For example, in an embodiment, the small regions 108a, 108b, 108c, 108d are respectively arranged at the four corners of the absorption region 10, and the four switches are respectively arranged on the four side surfaces 13 so that the path of holes moving from the absorption region 10 towards one or more of the small regions 108a, 108b, 108c, 108d is different from the path of electrons moving from the absorption region 10 towards one of the first doped regions.

[0131] In an embodiment, the second electrode 60 includes auxiliary electrodes 60a, 60b, 60c, 60d that are electrically coupled to the small regions 108a, 108b, 108c, 108d respectively. The auxiliary electrodes 60a, 60b, 60c, 60d are arranged on the first surface 21 of the substrate 20.

[0132] By having the second doped region 108 on the substrate 20 instead of the absorption region 10, all of the auxiliary electrodes 60a, 60b, 60c, 60d, the readout electrodes 330a, 330b, 330c, 330d, and the control electrodes 340a, 340b, 340c, 340d can be in the same plane above the first surface 21 of the substrate 20. Therefore, the height difference between any two of the auxiliary electrodes 60a, 60b, 60c, 60d, the readout electrodes 330a, 330b, 330c, 330d, and the control electrodes 340a, 340b, 340c, 340d can be reduced, whereby the subsequent manufacturing process will benefit from this design. Additionally, the area of the absorption region 10 that absorbs optical signals can be made larger.

[0133] FIG. 8C shows a top view of a photodetector device according to an embodiment. The photodetector device 800c in FIG. 8C is similar to the photodetector device 800a in FIG. 8A. The differences are described below. Unlike the arrangements of the readout electrodes 330a, 330b, 330c, 330d and the control electrodes 340a, 340b, 340c, 340d, the arrangements of the auxiliary electrodes 60a, 60b, 60c, 60d are different, and the arrangements of the small regions 108a, 108b, 108c, 108d are different. For example, four switches are respectively arranged at the four corners of the absorption region 10, and the small regions 108a, 108b, 108c, 108d and the auxiliary electrodes 60a, 60b, 60c, 60d are arranged on the respective side surfaces 13 of the absorption region 10.

[0134] FIG. 8D shows a top view of a photodetector device according to an embodiment. The photodetector device 800d is similar to the photodetector device 800a in FIG. 8A. The differences are described below. The photodetector device 800d includes eight switches (not labeled) that are electrically coupled to the absorption region 10 and are partially formed on the substrate 20, which is similar to the photodetector device 700d in FIG. 7D. The pixels of the photodetector device also include a plurality of control signals as described in FIG. 7D.

[0135] FIG. 8E shows a top view of a photodetection device according to an embodiment. The photodetection device 800e is similar to the photodetection device 800d in FIG. 8D. The differences are described below. Unlike the arrangement of the readout electrodes 330a, 330b, 330c, 330d, 330e, 330f, 330g, 330h and the arrangement of the control electrodes 340a, 340b, 340c, 340d, 340e, 340f, 340g, 340h, the arrangement of the sub-electrodes 60a, 60b, 60c, 60d is different, and the arrangement of the small regions 108a, 108b, 108c, 108d is different. For example, every other one of the eight switches is arranged at the four corners of the absorption region 10, respectively, and the small regions 108a, 108b, 108c, 108d and the sub-electrodes 60a, 60b, 60c, 60d are arranged on the respective side surfaces 13 of the absorption region 10.

[0136] FIG. 9A shows a schematic diagram of a photodetection apparatus according to an embodiment. The photodetection apparatus 900a includes pixels (not labeled) and column buses electrically coupled to the pixels. Each pixel includes a photodetection device and a plurality of readout circuits (not labeled) electrically coupled to the photodetection device and the column buses. The photodetection device can be any photodetection device as described in FIGS. 3A-3B, FIGS. 4A-4C, FIGS. 5A-5C, FIGS. 6A-6G, FIGS. 7A-7E, and FIGS. 8A-8E. For example, the photodetection device 300a in FIG. 3B is shown in FIG. 9A. Each of the readout circuits is similar to the readout circuit as described in FIG. 2E. The differences are described below. Each of the readout circuits is electrically coupled to each first doped region of the switches of the photodetection device to process a first type of carrier. For example, when the first doped region is of the n-type, the readout circuit processes the electrons collected from each first doped region for further use.

[0137] The number of readout circuits is the same as the number of switches. That is, the photodetection device includes N switches electrically coupled to the absorption region 10 and partially formed on the substrate 20, and the pixel of the photodetection device further includes Z readout circuits electrically coupled to the photodetection device, where Z = N. For example, in FIGS. 3A - 3B, FIGS. 4A - 4C, FIGS. 5A - 5C, and FIGS. 6A - 6G, the number of switches of the photodetection device is 4, and the number of readout circuits is 2. For other examples, in FIGS. 7A - 7C and FIGS. 8A - 8C, the number of switches of the photodetection device is 2, and the number of readout circuits is 4. For other examples, in FIGS. 7D - 7E and FIGS. 8D - 8E, the number of switches of the photodetection device is 8, and the number of readout circuits is 8.

[0138] FIG. 9B shows a schematic diagram of a photodetection device according to an embodiment. The photodetection device 900b is the same as the photodetection device 900a in FIG. 9A. The differences are described below. Similar to the readout circuit as described in FIG. 2F, the readout circuit of the photodetection device 900b further includes a voltage - controlled transistor 130A between the first / second switches of the photodetection device 300a and the capacitor 150A.

[0139] FIG. 10A shows a cross - sectional view of a photodetection device according to an embodiment. The photodetection device includes an absorption region 10 and a substrate 20 that supports the absorption region 10. The absorption region 10 is the same as the absorption region 10 as described in FIG. 1A. The substrate 20 is the same as the substrate 20 as described in FIG. 1A. The difference between the photodetection device 1000a in FIG. 10A and the photodetection device 100a in FIG. 1A is described below. In an embodiment, the photodetection device 1000a further includes a first contact region 204 separated from the absorption region 10 on the substrate 20. The photodetection device 1000a further includes a second contact region 103 on the absorption region 10.

[0140] In some embodiments, the second contact region 103 is of a conductive type. The first contact region 204 is of a conductive type different from that of the second contact region 103. In some embodiments, the second contact region 103 includes a dopant having a peak doping concentration higher than the first peak doping concentration of the absorption region 10. For example, it can be in the range of 1×10 18 cm -3 to 5×10 20 cm -3 In some embodiments, the first contact region 204 includes a dopant having a peak doping concentration higher than the second peak doping concentration of the second dopant of the substrate 20. For example, it can be in the range of 1×10 18 cm -3 to 5×10 20 cm -3 In some embodiments, the second contact region 103 is not disposed on the first contact region 204 along a direction D1 substantially perpendicular to the first surface 21 of the substrate 20.

[0141] The photodetector device includes a first electrode 140 coupled to the first contact region 204 and a second electrode 160 coupled to the second contact region 103. The second electrode 160 is on the first surface 11 of the absorption region 10. The first electrode 140 is on the first surface 21 of the substrate 20. In some embodiments, the substrate 20 of the photodetector device 1000a includes a conductive region 201 similar to the conductive region 201 as described in FIG. 1A.

[0142] In some embodiments, the photodetector device 1000a further includes a third contact region 208 in the substrate 20. In some embodiments, the third contact region 208 is between the second contact region 103 and the first contact region 204. The third contact region 208 is of the same conductive type as the second contact region 103. The third contact region 208 includes a conductive type different from that of the first contact region 204. In some embodiments, the third contact region 208 includes a dopant having a peak doping concentration higher than the second peak doping concentration of the conductive region 201. For example, 1×10 18 cm -3 and 5×10 20cm -3 can be between.

[0143] In some embodiments, the distance between the first surface 21 of the substrate 20 and the location of the first contact region 204 having the peak dopant concentration is less than 30 nm. In some embodiments, the distance between the first surface 21 of the substrate 20 and the location of the third contact region 208 having the peak dopant concentration is less than 30 nm.

[0144] In some embodiments, the third contact region 208 can be entirely overlapped with the conductive region 201. Both the third contact region 208 and the first contact region 204 are below the first surface 21 of the substrate 20.

[0145] In some embodiments, the photodetector device further comprises a third electrode 130 electrically coupled to the third contact region 208. The third electrode 130 and the first electrode 140 are formed on the same plane on the first surface 21 of the substrate 20, and thus, the height difference between the third electrode 130 and the first electrode 140 can be reduced, which is beneficial for the subsequent manufacturing process.

[0146] The photodetector device 1000a can be a lock-in pixel or an avalanche phototransistor according to a circuit electrically coupled to the photodetector device 1000a and / or the operating method of the photodetector device 1000a.

[0147] For example, when the photodetector device 1000a serves as a lock-in pixel, the third contact region 208 and the first contact region 204 can be regarded as switches. The reading circuit is electrically coupled to the first contact region 204 through the first electrode 140, and a control signal, which is a modulation signal, is electrically coupled to the third contact region 208 through the third electrode 130 to control the on / off state of the switch, and voltage or ground may be applied to the second contact region 103 to remove carriers not collected by the first contact region 204. The lock-in pixel can be included in an indirect TOF system.

[0148] In one embodiment, when the photodetection device 1000a is provided as an avalanche phototransistor, a part of the substrate 20 or a part of the conduction region 201 through which carriers pass between the third contact region 208 and the first contact region 204 is provided as the multiplication region M during the operation of the photodetection device 1000a. In the multiplication region, optical carriers generate additional electrons and holes through impact ionization, which initiates a chain reaction of avalanche multiplication. As a result, the photodetection device 100a has a gain. In one embodiment, the substrate 20 supports the absorption region 10 and can simultaneously amplify carriers by avalanche multiplication. In one embodiment, the third contact region 208 can be a charge region. The avalanche phototransistor can be directly included in the TOF system.

[0149] A method for operating the photodetection device 1000a capable of collecting electrons in FIG. 10A includes generating a first total current and applying a first voltage to the first electrode 140, a second voltage to the second electrode 160, and a third voltage to the third electrode 130 to form a pn junction with a reverse bias applied between the first electrode 140 and the third electrode 130, and receiving an incident light beam in the absorption region 10 to generate a second total current greater than the first total current.

[0150] In one embodiment, the first voltage is greater than the second voltage. In one embodiment, the third voltage is between the first voltage and the second voltage.

[0151] In one embodiment, the first total current includes a first current and a second current. The first current flows from the first electrode 140 to the third electrode 130. The second current flows from the first electrode 140 to the second electrode 160.

[0152] In one embodiment, the second total current includes a third current. The third current flows from the first electrode 140 to the second electrode 160.

[0153] In one embodiment, the second total current includes a third current and a fourth current. The fourth current flows from the first electrode 140 to the third electrode 130.

[0154] In one embodiment, the second voltage applied to the first electrode is, for example, 0 volts.

[0155] In one embodiment, the third voltage can be selected to sweep optical carriers from the absorption region 10 to the multiplication region, i.e., to a part of the substrate 20, or to a part of the conduction region 201 between the third contact region 208 and the first contact region 204. In one embodiment, the voltage difference between the second voltage and the third voltage is smaller than the voltage difference between the first voltage and the third voltage in order to facilitate the movement of optical carriers from the absorption region 10 to the multiplication region in the substrate 20 so as to multiply the optical carriers. For example, when the second voltage applied to the second electrode 160 is 0 volts, the third voltage applied to the third electrode 130 can be 1V, and the first voltage applied to the first electrode 140 can be 7V.

[0156] In one embodiment, the voltage difference between the first voltage and the third voltage is smaller than the avalanche breakdown voltage of the photodetector device 1000a, at which avalanche breakdown voltage the photodetector device 1000a initiates a chain reaction of avalanche multiplication to operate the multiplication region in a linear mode.

[0157] In one embodiment, the voltage difference between the first voltage and the third voltage is greater than the avalanche breakdown voltage of the photodetector device 1000a, at which avalanche breakdown voltage the photodetector device 1000a initiates a chain reaction of avalanche multiplication to operate the multiplication region in a Geiger mode.

[0158] In one embodiment, the carriers collected by the first contact region 204 can be further processed by a circuit electrically coupled to the photodetector device 1000a.

[0159] In one embodiment, carriers not collected by the first contact region 204 can move toward the second contact region 103 and can be further removed by a circuit electrically coupled to the photodetection device 1000a.

[0160] Similarly, by the concentration and material design of the absorption region 10 and, in one embodiment, the carrier conduction layer which is the substrate 20, the photodetection device 1000a can have a lower dark current.

[0161] FIG. 10B shows a top view of a photodetection device according to an embodiment. FIG. 10C shows a cross-sectional view along the line A-A' in FIG. 10B according to an embodiment. The photodetection device 1000b in FIG. 10B is similar to the photodetection device 1000a in FIG. 10A. The differences are described below. Preferably, the photodetection device 1000b serves as an avalanche phototransistor. The photodetection device 1000b further includes a correction element 203 integrated with the substrate 20. The correction element 203 is for correcting the position where multiplication occurs in the substrate 20. In one embodiment, the resistance of the correction element 203 is higher than the resistance of the substrate 20 so as to correct the position where multiplication occurs in the substrate 20. Thus, more carriers can pass through the location where the strongest electric field is located and the avalanche multiplication gain is increased.

[0162] For example, the modifying element 203 is a trench formed on the first surface 21 of the substrate 20. The trench can prevent carriers from passing through a defined area of the substrate 20, thereby reducing the area of the substrate 20 through which the carriers pass. The trench has a depth, and the ratio of the depth to the thickness of the substrate 20 can be between 10% and 90%. The first contact region 204 is exposed in the trench so as to be electrically coupled to the first electrode 140. In some embodiments, the width of the trench may be larger than, substantially equal to, or smaller than the width of the first contact region 204. In some embodiments, the width of the trench can be larger than the width of the first contact region 204 so as to allow carriers to pass through a high electric field region adjacent to the first contact region 204.

[0163] By the modifying element 203, carriers such as electrons, for example, are caused to pass through a multiplication region where the strongest electric field is located, such as a region adjacent to the first contact region 204, thereby increasing the avalanche multiplication gain.

[0164] In some embodiments, the first electrode 140 is formed in the trench. The height difference is between the third electrode 130 and the first electrode 140.

[0165] In some embodiments, the conduction region 201 can be separated from the third contact region 208, can overlap a part of the third contact region 208, can overlap the entire third contact region 208, can be in contact with the corner of the trench, or can be partially overlapped with the first contact region 204.

[0166] In some embodiments, the trench can be filled with an insulating material.

[0167] FIG. 10D shows a top view of a photodetector device according to an embodiment. FIG. 10E shows a cross-sectional view along line A-A' in FIG. 10D according to an embodiment. FIG. 10F shows a cross-sectional view along line B-B' in FIG. 10D according to an embodiment. The photodetector device 1000d in FIG. 10D is similar to the photodetector device 1000b in FIG. 10B. The differences are described below. In one embodiment, the distance between the first surface 21 of the substrate 20 and the location of the third contact region 208 having a peak dopant concentration is greater than 30 nm. In one embodiment, the photodetector device 1000d further includes a recess 205 formed in the first surface 21 of the substrate 20 to expose the third contact region 208. The third electrode 130 is formed in the recess 205 to be electrically coupled to the third contact region 208. Since the distance between the first surface 21 of the substrate 20 and the location of the third contact region 208 having a peak dopant concentration is greater than 30 nm, the distance between the third contact region 208 and the first contact region 204 becomes shorter, which further restricts the movement path of the carriers so that the strongest electric field passes through the location where more carriers are located. Therefore, the avalanche multiplication gain is further improved. In one embodiment, the recess 205 may be filled with an insulating material. The first electrode may include an interconnect or a plug.

[0168] FIG. 10G shows a cross-sectional view of a photodetector device according to an embodiment. The photodetector device 1000g in FIG. 10G is similar to the photodetector device 1000d in FIG. 10D. The differences are described below. In one embodiment, the photodetector device 1000g includes a plurality of third contact regions 208 and a plurality of first contact regions 204. The third contact regions 208 and the plurality of first contact regions 204 are arranged in a staggered pattern. With this design, a plurality of multiplication regions can be formed between the plurality of third contact regions 208 and the plurality of first contact regions 204, providing a more uniform electric field profile compared to the photodetector device 1000d. Also, carriers mainly drift along a direction D1 that is substantially perpendicular to the first surface 21 of the substrate 20, which increases the speed of the photodetector device 1000g because the vertical movement distance is usually shorter.

[0169] In one embodiment, the second contact region 103 is disposed on the first contact region 204 along a direction D1 that is substantially perpendicular to the first surface 21 of the substrate 20. In one embodiment, the maximum distance d2 between the two outermost third contact regions 208 is greater than the width w3 of the conduction region 201, which causes carriers generated from the absorption region 10 to pass through the plurality of multiplication regions between the plurality of third contact regions 208 and the plurality of first contact regions 204 instead of moving to other undesirable regions in the substrate 20.

[0170] In one embodiment, the plurality of third contact regions 208 may be separated from each other. In one embodiment, the plurality of first contact regions 204 may be separated from each other. In one embodiment, the plurality of third contact regions 208 may be a continuous region. In one embodiment, the plurality of first contact regions 204 may be a continuous region.

[0171] In one embodiment, the first contact regions 204 may be arranged in a meshed configuration with each other in a view from above a first plane (not shown). In one embodiment, the third contact regions 208 may be arranged in a meshed configuration with each other in a view from above a second plane (not shown) that is different from the first plane.

[0172] In some embodiments, one or more third electrodes 130 can be electrically coupled to the third contact region 208 through any suitable structure, such as a via, from another cross-sectional view of the photodetection device 1000g taken from a different plane. In some embodiments, one or more first electrodes 140 can be electrically coupled to the first contact region 204 through any suitable structure, such as a via, from another cross-sectional view of the photodetection device 1000g taken from a different plane.

[0173] FIG. 10H shows a cross-sectional view of a photodetection device according to some embodiments. The photodetection device 1000h in FIG. 10H is similar to the photodetection device 1000a in FIG. 10A. The differences are described below.

[0174] The photodetection device 1000h further includes an intermediate doped region 210 on the substrate 20 that can be partially overlapped with the conductive region 201. The intermediate doped region 210 has the same conductivity type as that of the third contact region 208. The intermediate doped region 210 includes a dopant having a peak doping concentration lower than the peak doping concentration of the third contact region 208. For example, it can be between 1×10 16 cm -3 and 1×10 18 cm -3 and.

[0175] 18 cm -3 and 1×10 20 cm -3 and.

[0176] ​The intermediate doped region 210 is between the lower doped region 212 and the second contact region 103 along a direction substantially perpendicular to the first surface 21 of the substrate 20. In certain embodiments, the position where the peak doping concentration of the lower doped region 212 exists is deeper than the position where the peak doping concentration of the intermediate doped region 210 exists.

[0177] In certain embodiments, the depth of the third contact region 208 is less than the depth of the first contact region 204. The depth is measured from the first surface 21 of the substrate 20 along a direction substantially perpendicular to the first surface 21 of the substrate 20. The depth is up to the position where the dopant profile of the dopant reaches a specific concentration such as 1×10 15 cm -3 and so on.

[0178] The multiplication region M can be formed between the lower doped region 212 and the intermediate doped region 210 during the operation of the photodetector device 1000h. The multiplication region M is configured to receive one or more charge carriers from the intermediate doped region 210 and generate one or more additional charge carriers. The multiplication region M is perpendicular to the first surface 21 and has a thickness sufficient for generating one or more additional charge carriers from one or more carriers generated in the absorption region 10. The thickness of the multiplication region M can be in the range between, for example, 100 and 500 nanometers (nm). The thickness can determine the voltage drop of the multiplication region M to reach avalanche breakdown. For example, a thickness of 100 nm corresponds to a voltage drop of about 5 to 6 volts required to reach avalanche breakdown in the multiplication region M. In another example, a thickness of 300 nm corresponds to a voltage drop of about 13 to 14 volts required to reach avalanche breakdown in the multiplication region M.

[0179] In certain embodiments, the shape of the third contact region 208, the shape of the first contact region 204, the shape of the third electrode 130, and the shape of the first electrode 140 are not limited, but can be rings.

[0180] Compared with the photodetector 1000b in FIG. 10C, the multiplication region M in the photodetector 1000h can be formed in the bulk region of the substrate 20, which avoids the defects that may exist on the trench surface described in FIG. 10C. As a result, the dark current is further reduced. Furthermore, the height difference between the third electrode 130 and the first electrode 140 can be reduced, whereby the subsequent manufacturing process will benefit from this design.

[0181] FIG. 10I shows a cross-sectional view of a photodetector according to an embodiment. The photodetector 1000i in FIG. 10I is similar to the photodetector 1000h in FIG. 10H. The differences are described below. The substrate 20 includes a base portion 20a, an upper portion 20b, and an intermediate portion 20c. The intermediate portion 20c is between the base portion 20a and the upper portion 20b. The absorption region 10, the second contact region 103, and the conduction region 201 are in the upper portion 20b. The third contact region 208 is in the intermediate portion 20c. The first contact region 204 is in the base portion 20a. The upper portion 20b has a width smaller than the width of the intermediate portion 20c, and the third contact region 208 is exposed to be electrically coupled to the third electrode 130. The intermediate portion 20c has a width smaller than the width of the base portion 20a, and the first contact region 204 is exposed to be electrically coupled to the first electrode 140.

[0182] The intermediate doped region 210 is in the intermediate portion 20c. The lower doped region 212 is in the base portion 20a. Compared with the photodetector 1000b in FIG. 10C, the multiplication region M in the photodetector 1000h can be formed in the bulk region of the intermediate portion 20c, which avoids the defects that may exist on the trench surface described in FIG. 10C. As a result, the dark current is further reduced.

[0183] FIG. 11A shows a cross-sectional view of a photodetector according to an embodiment. The photodetector 1100a in FIG. 11A is similar to the photodetector 1000a in FIG. 10A. The differences are described below.

[0184] The second contact region 103 is in the substrate 20. In other words, the peak doping concentration of the second contact region 103 is located in the substrate 20. In certain embodiments, the second contact region 103 is below the first surface 21 of the substrate 20 and is in direct contact with the absorption region 10. For example, the second contact region 103 may contact or overlap with one of the side surfaces 13 of the absorption region 10 that is opposite to the third contact region 208 and / or the first contact region 204. As a result, carriers generated from the absorption region 10 can move from the absorption region 10, through the heterointerface between the absorption region 10 and the substrate 20, towards the second contact region 103. The second electrode 160 is on the first surface 21 of the substrate 20.

[0185] By having the second contact region 103 in the substrate 20 instead of in the absorption region 10, the second electrode 160, the first electrode 140, and the third electrode 130 can all be formed in the same plane above the first surface 21 of the substrate 20. Therefore, the height difference between any two of the second electrode 160, the third electrode 130, and the first electrode 140 can be reduced, whereby the subsequent manufacturing process will benefit from this design. Additionally, the area of the absorption region 10 that absorbs optical signals can be made larger.

[0186] FIG. 11B shows a top view of a photodetector device according to an embodiment. FIG. 11C shows a cross-sectional view along line A-A' in FIG. 11B according to an embodiment. The photodetector device 1100b in FIG. 11B is similar to the photodetector device 1100a in FIG. 11A. The differences are described below. The photodetector device 1100b further includes a modification element 203 integrated with the substrate 20. The modification element 203 is similar to the modification element 203 as described in FIGS. 10B and 10C.

[0187] FIG. 11D shows a top view of a photodetection device according to an embodiment. FIG. 11E shows a cross-sectional view along line A-A' in FIG. 11D according to an embodiment. A cross-sectional view along line B-B' in FIG. 11D is the same as FIG. 10F. The photodetection device 1100d in FIG. 11D is similar to the photodetection device 1100b in FIG. 11B. The differences are described below. The third contact region 208 is similar to the third contact region 208 in FIGS. 10D and 10E. In addition, the photodetection device 1100d further includes a recess 205 similar to the recess 205 as described in FIGS. 10D and 10F, and the third electrode 130 is formed in the recess 205 to be electrically coupled to the third contact region 208.

[0188] FIG. 12A shows a cross-sectional view of a photodetection device according to an embodiment. The photodetection device 1200a in FIG. 12A is similar to the photodetection device 1000b in FIG. 10C. The differences are described below. From the cross-sectional view of the photodetection device, the photodetection device 1200a includes two third contact regions 208, two first contact regions 204, two third electrodes 130, and two first electrodes 140. The third contact regions 208 are disposed on two opposite sides of the absorption region 10, and the two third electrodes 130 are electrically coupled to the respective third contact regions 208. The first contact regions 204 are disposed on two opposite sides of the absorption region 10, and the first electrodes 140 are electrically coupled to the respective first contact regions 204. The distance between the third contact regions 208 is smaller than the distance of the first contact regions 204. The substrate 20 further includes a waveguide 206 associated with the absorption region 10 to guide and / or confine an incident optical signal passing through a defined region of the substrate 20. For example, the waveguide 206 can be a ridge defined by two trenches 207. The ridge has a width larger than the width of the absorption region 10. The incident optical signal can be confined and propagated along the ridge 206. The trenches can be similar to the trenches mentioned in FIGS. 10B and 10C, and can also be modification elements 203 as mentioned in FIGS. 10B and 10C. For example, carriers are passed through a multiplication region where the strongest electric field is located, such as a region near each corner of the trench, thereby increasing the avalanche multiplication gain. Similar to FIGS. 10B and 10C, each of the first contact regions 204 is exposed in the respective trench 206 to be electrically coupled to the respective first electrode 140.

[0189] FIG. 12B shows a cross-sectional view of a photodetection device according to an embodiment. The photodetection device 1200b in FIG. 12B is similar to the photodetection device 1100a in FIG. 12A. The differences are described below. The third contact region 208 is similar to the third contact region 208 in FIGS. 10D and 10E. For example, the distance between the first surface 21 of the substrate 20 and the location of each of the third contact regions 208 having a peak dopant concentration is greater than 30 nm.

[0190] FIG. 12C shows a cross-sectional view of a photodetector according to an embodiment. The photodetector 1200c in FIG. 12C is similar to the photodetector 1000g in FIG. 10G. The differences are described below. The photodetector 1200c further includes a waveguide 206 integrated with the substrate 20, and the waveguide 206 is similar to the waveguide 206 described in FIG. 12A.

[0191] FIG. 13A shows a cross-sectional view of a photodetector according to an embodiment. The photodetector includes an absorption region 10 and a substrate 20 that supports the absorption region 10. The absorption region 10 is similar to the absorption region 10 as described in FIG. 1A. The substrate 20 is similar to the substrate 20 as described in FIG. 1A. The differences between the photodetector 1300a in FIG. 13A and the photodetector 100a in FIG. 1A are described below.

[0192] The photodetector 1300a includes a collector region 1302 and an emitter region 1304 separated from the collector region 1302. In one embodiment, the collector region 1302 is in the absorption region 10. The emitter region 1304 is outside the absorption region 10 and is on the substrate 20. The collector region 1302 is for collecting amplified optical carriers generated from the absorption region 10. The collector region 1302 is of a conductive type. The emitter region 1304 is of the same conductive type as the collector region 1302. The conductive type of the absorption region 10 is the same as that of the collector region 1302. For example, the conductive type of the absorption region 10 is p-type, and the conductive types of the collector region 1302 and the emitter region 1304 are p-type. In one embodiment, the collector region 1302 includes a dopant and has a dopant profile with a peak dopant concentration higher than the first peak doping concentration of the absorption region 10. For example, 5×10 18 cm -3 to 5×10 20 cm -3 and can be in the range of.

[0193] In one embodiment, the emitter region 1304 has a dopant profile with a peak dopant concentration that includes a dopant and is higher than the second peak doping concentration of the second dopant of the substrate 20. For example, 1×10 17 cm -3 to 5×10 18 cm -3 can be in the range of.

[0194] The photodetector device 1300a includes a first electrode 1330 electrically coupled to the collector region 1302 and a second electrode 1340 electrically coupled to the emitter region 1304. The first electrode 1330 serves as a collector electrode. The second electrode 1340 serves as an emitter electrode.

[0195] In one embodiment, similar to the conduction region described in FIG. 1A, a conduction region (not shown) can be formed in a carrier conduction layer that is the substrate 20 in one embodiment. The conduction region 201 is between the emitter region 1304 and the absorption region 10. In one embodiment, the conduction region 201 is partially overlapped with the absorption region 10 and the emitter region 1304 to limit the path of carriers generated from the absorption region 10 and moving toward the emitter region 1304. In one embodiment, the conduction region 201 has a depth measured from the first surface 21 of the substrate 20 along a direction substantially perpendicular to the first surface 21 of the substrate 20. The depth is up to the position where the dopant profile of the second dopant reaches a specific concentration such as 1×10 15 cm -3 and so on.

[0196] Similarly, depending on the concentration and material design of the absorption region 10 and the carrier conduction layer which is the substrate 20 in one embodiment, the photodetector device 1300a can have a lower dark current.

[0197] In one embodiment, a method for operating a photodetector device 1300a includes generating a PN junction with a reverse bias applied between the absorption region 10 and the substrate 20 and a PN junction with a forward bias applied between the substrate 20 and the emitter region 1304, and receiving an incident light beam in the absorption region 10 to generate an amplified photocurrent.

[0198] For example, the photodetector device 1300a may include a p-doped emitter region 1304, an n-doped substrate 20, a p-doped absorption region 10, and a p-doped collector region 1302. A forward bias is applied to the PN junction between the p-doped emitter region 1304 and the n-doped substrate 20 such that a hole current is emitted to the n-doped substrate 20. A reverse bias is applied to the PN junction between the p-doped absorption region 10 and the n-doped substrate 20 such that the emitted hole current is collected by the first electrode 1330. When a light beam (e.g., a light beam at 940 nm, 1310 nm, or any suitable wavelength) is incident on the photodetector device 1300a, optical carriers including electrons and holes are generated in the absorption region 10. The holes generated by the light are collected by the first electrode 1330. The electrons generated by the light are directed towards the n-doped substrate 20, which increases the forward bias due to charge neutrality. The increased forward bias further increases the hole current collected by the first electrode 1330, resulting in an amplified hole current generated by the photodetector device 1300a.

[0199] Accordingly, the second electrical signal collected by the collector region 1302 is larger than the first electrical signal generated by the absorption region 10, whereby the photodetector device 1300a has a gain and, by extension, an improved signal-to-noise ratio.

[0200] In one embodiment, a method for operating a photodetector device 1300a capable of collecting holes includes applying a first voltage V1 to a first electrode 1330 and a second voltage V2 to a second electrode 1340 to generate a first current flowing from the second electrode 1340 to the first electrode 1330, where the second voltage V2 is higher than the first voltage V1; and receiving an incident light beam in an absorption region 10 to generate a second current flowing from the second electrode 1340 to the first electrode 1330, where the second current is greater than the first current, after the absorption region 10 generates optical carriers from the incident light beam.

[0201] In one embodiment, a method for operating a photodetector device 1300a capable of collecting holes includes applying a second voltage V2 to a second electrode 1340 to form a forward bias between an emitter region 1304 and a substrate 20 to form a first hole current, and applying a first voltage to a first electrode 1330 to form a reverse bias between the substrate 20 and the absorption region 10 to collect a portion of the first hole current, where the second voltage V2 is higher than the first voltage V1; receiving an incident light beam in an absorption region 10 to generate optical carriers including electrons and holes; amplifying a portion of the holes of the optical carriers to generate a second hole current; and collecting a portion of the second hole current by a collector region 1302, where the second hole current is greater than the first hole current.

[0202] FIG. 13B shows a cross-sectional view of a photodetector according to an embodiment. The photodetector 1300b in FIG. 13B is similar to the photodetector 1300a in FIG. 13A. The differences are described below. The photodetector further includes a base region 1308 and a third electrode 1360 electrically coupled to the base region 1308. The third electrode 1360 serves as a base electrode. In an embodiment, the base region 1308 is between the collector region 1302 and the emitter region 1304. The base region 1308 has a conductivity type different from that of the collector region 1302. In an embodiment, the base region 1308 is on the substrate 20.

[0203] In an embodiment, the base region 1308 includes a dopant and has a dopant profile with a peak dopant concentration higher than the second peak doping concentration of the second dopant in the substrate 20, for example, 1×10 17 cm -3 to 5×10 18 cm -3 and can be in the range of.

[0204] The third electrode 1360 is for applying a bias to the base contact region 1308. In an embodiment, the third electrode 1360 has an opposite type and is for removing optical carriers that are not collected by the first electrode 1330 during the operation of the photodetector 1300b. For example, when the photodetector 1300b is configured to collect holes that are further processed by a circuit or the like, the third electrode 1360 is for removing electrons. Therefore, the photodetector 1300b can have improved reliability.

[0205] In one embodiment, a method for operating a photodetector device 1300b capable of collecting holes includes applying a second voltage V2 to a second electrode 1340 to form a forward bias between an emitter region 1304 and a substrate 20 to form a first hole current, and applying a first voltage to a first electrode 1330 to form a reverse bias between the substrate 20 and an absorption region 10 to collect a portion of the first hole current, wherein the second voltage V2 is higher than the first voltage V1; applying a third voltage to a third electrode 60 electrically coupled to a base contact region 1308 of the photodetector device; receiving an incident light beam in the absorption region 10 to generate optical carriers including electrons and holes; amplifying a portion of the holes of the optical carriers to generate a second hole current; and collecting a portion of the second hole current by a collector region 1302, wherein the third voltage V3 is between the first voltage V1 and the second voltage V2.

[0206] The reverse bias is formed across a pn junction between the collector region 1302 and the base region 1308, and the forward bias is formed across a pn junction between the emitter region 1304 and the base region 1308. In one embodiment, the step of applying the third voltage V3 to the third electrode 1360 and the steps of applying the first voltage V1 to the first electrode 1330 and applying the second voltage V2 to the second electrode 1340 are operated simultaneously.

[0207] In one embodiment, the arrangement of the third electrode 1360, the first electrode 1330, and the second electrode 1340 may be different from the arrangement of the base region 1308, the collector region 1302, and the emitter region 1304. For example, in one embodiment, the second electrode 1340 is between the first electrode 1330 and the third electrode 1360. The emitter region 1304 is between the collector region 1302 and the base region 1308.

[0208] FIG. 14A shows a cross-sectional view of a portion of a photodetector device according to an embodiment. The photodetector device can be any of the photodetector devices described previously. The photodetector device further includes a protective layer 1400 on a first surface 11 of the absorption region 10. In some embodiments, the protective layer 1400 further covers a portion of the first surface 21 of the substrate 20, and the readout electrodes 330a, 330b and the control electrodes 340a, 340b may or may not be on the first surface 1401 of the protective layer 1400. In some embodiments, the absorption region 10 is protruded from the first surface 21 of the substrate 20, and the protective layer 1400 further covers a side surface 13 of the absorption region 10 exposed from the substrate 20. That is, the protective layer 1400 can be formed conformally on the absorption region 10 and the substrate 20, as shown in FIG. 14B. In some embodiments, the second electrode 60 is formed on a surface of the protective layer 1400 that is higher than the surface of the protective layer 1400 on which the readout electrodes 330a, 330b and the control electrodes 340a, 340b can be formed. In some embodiments, the control electrodes 340a, 340b, the readout electrodes 330a, 330b, and the second electrode 60 are all disposed on a first surface of a carrier conduction layer. That is, the control electrodes 340a, 340b, the readout electrodes 330a, 330b, and the second electrode 60 are on the same side of a carrier conduction layer which is the protective layer 1400 in some embodiments, which is beneficial for subsequent back-end fabrication processes.

[0209] The protective layer 1400 is amorphous silicon, polysilicon, epitaxial silicon, aluminum oxide (e.g., Al x O y )), silicon oxide (e.g., Si x O y) ), germanium oxide (e.g., Ge x O y ), germanium silicon (e.g., GeSi), silicon nitride family (e.g., Si x N y ), high-k materials (e.g., HfO x ), ZnO x ), LaO x ), LaSiO x) and combinations thereof. The presence of the protective layer 1400 can have various effects. For example, the protective layer 1400 can serve as a surface protection layer for the absorption region 10, which can reduce the dark current or leakage current caused by defects occurring at the exposed surface of the absorption region 10. In certain embodiments, the protective layer 1400 can have a thickness between 20 nm and 100 nm. FIG. 14B shows a cross-sectional view along a line passing through the second doped region 108 of the photodetector device according to certain embodiments. In certain embodiments, a part of the doped region in the absorption region 10, such as the second doped region 108 or the second contact region 103, can be formed in the corresponding part of the protective layer 1400. That is, the dopant of the doped region, such as the second doped region 108 or the second contact region 103, can be in the corresponding part of the protective layer 1400 between the absorption region 10 and the respective electrodes.

[0210] Figure 14C shows a top view of a photodetection device according to an embodiment. Figure 14D shows a cross-sectional view along line A-A' in Figure 14C according to an embodiment. Figure 14E shows a cross-sectional view along line B-B' in Figure 14C according to an embodiment. The photodetection device 1400c in Figure 14C is similar to the photodetection device 300a in Figure 3A. The differences are described below. The absorption region 10 is completely embedded in the substrate 20. The photodetection device 1400c includes a protective layer 1400 on the absorption region 10 and the substrate 20, and the protective layer 1400 is similar to the protective layer 1400 described in Figure 14A. In some embodiments, the thickness of the protective layer 1400 can be between 100 nm and 500 nm. The readout electrodes 330a, 330b and the control electrodes 340a, 340b are on the first surface 1401 of the protective layer 1400 and are separated from the absorption region 10. In some embodiments, the readout electrodes 330a, 330b, the control electrodes 340a, 340b, and the second electrode 60 are formed in the same plane in the protective layer 1400, so the height difference between the electrodes can be reduced. The carrier conduction layer is in the protective layer 1400 instead of the substrate 20. That is, the heterointerface is between the protective layer 1400 and the absorption region 10. In some embodiments, the first surface 11 of the absorption region 10 is at least partially in direct contact with the protective layer 1400, so that a heterointerface is formed between the absorption region 10 and the protective layer 1400. The substrate 20 can be intrinsic and is not limited to the description in Figure 1A.

[0211] In some embodiments, the second doped region 108 is similar to the second doped region 108 described in Figure 3A. The differences are described below. The second doped region 108 is in the protective layer 1400 and the absorption region 10. In some embodiments, the second doped region 108 has a depth greater than the thickness of the protective layer 1400 so as to guide carriers of the second type to move towards the second electrode 60 and to be further removed by a circuit. The depth is measured from the first surface 1401 of the protective layer 1400 along a direction substantially perpendicular to the first surface 1401 of the protective layer 1400. The depth is such that the dopant profile of the fourth dopant is 1×1015 cm -3 up to the position where a specific concentration such as this is reached.

[0212] Similar to the light detection device 100a in FIG. 1A, in one embodiment, the doping concentration of the first dopant at the heterointerface between the absorption region 10 and the carrier conduction layer, which is the protective layer 1400 in one embodiment, is 1×10 16 cm -3 or more. In one embodiment, the doping concentration of the first dopant at the heterointerface is 1×10 16 cm -3 and 1×10 20 cm -3 or between 1×10 17 cm -3 and 1×10 20 cm -3 and may be between 1×10 12 cm -3 and 1×10 17 cm -3 In one embodiment, the doping concentration of the second dopant at the heterointerface is lower than the doping concentration of the first dopant at the heterointerface. In one embodiment, the doping concentration of the second dopant at the heterointerface is between 1×10

[0213] In one embodiment, the concentration of the stepwise doping profile of the first dopant is gradually reduced from the second surface 12 to the first surface 11 of the absorption region 10 so as to facilitate the movement of carriers such as electrons when the first doped regions 302a, 302b are of n-type.

[0214] In one embodiment, the first switch (not labeled) and the second switch (not labeled) are partially formed in the carrier conduction layer, which is the protective layer 1400 in one embodiment. In one embodiment, the first doped regions 302a, 302b are in the protective layer 1400. In one embodiment, the third peak doping concentration of the first doped regions 302a, 302b is in the protective layer 1400.

[0215] In one embodiment, the depth of each of the first doped regions 302a, 302b is less than the thickness of the protective layer 1400. The depth is measured from the first surface 1401 of the protective layer 1400 to the position where the dopant profile reaches a specific concentration such as 1×10 15 cm -3 and so on.

[0216] In one embodiment, absorption functions and carrier control functions such as carrier demodulation and carrier collection operate in the absorption region 10 and, in one embodiment, the carrier conduction layer which is the protective layer 1400, respectively.

[0217] In one embodiment, the conduction region 201 may be formed in the carrier conduction layer which is the protective layer 1400 in one embodiment. The conduction region 201 may be similar to the conduction region 201 described in FIG. 3A, and such a conduction region 201 overlaps with a part of the first doped regions 302a, 302b in the protective layer 1400. The differences are described below. In one embodiment, the conduction region 201 has a depth greater than or equal to the thickness of the protective layer 1400 so as to restrict and guide carriers with the first type and move them toward one of the first doped regions 302a, 302b. The depth is measured from the first surface 1401 of the protective layer 1400 along a direction substantially perpendicular to the first surface 1401 of the protective layer 1400. The depth is up to the position where the dopant profile of the second dopant reaches a specific concentration such as 1×10 15 cm -3 and so on.

[0218] In one embodiment, the width of the absorption region 10 is smaller than the distance between the two control electrodes 340a, 340b, which can reduce the leakage current between the two control electrodes 340a, 340b. FIG. 14F shows a cross-sectional view of a photodetection device according to an embodiment. The photodetection device 1400f in FIG. 14F is similar to the photodetection device 1400e in FIG. 14E. The differences are described below. The absorption region 10 is partially embedded in the substrate 20. The protective layer 1400 is conformally formed on the absorption region 10 and the substrate 20 to cover the exposed side surface 13 of the absorption region 10. The conductive region 201 can surround the absorption region 10 or overlap with all of the surface of the absorption region 10, that is, it can overlap with the first surface 11, the second surface 12, and all of the side surfaces 13 of the absorption region 10.

[0219] In one embodiment, the depth of each of the first doped regions 302a, 302b is greater than the thickness of the protective layer 1400. The depth is measured from the first surface 1401 of the protective layer 1400 to the position where the dopant profile reaches a specific concentration such as 1×10 15 cm -3 In one embodiment, the depth of each of the first doped regions 302a, 302b is smaller than the thickness of the protective layer 1400. The depth is measured from the first surface 1401 of the protective layer 1400 to the position where the dopant profile reaches a specific concentration such as 1×10 15 cm -3 and reaches a specific concentration.

[0220] FIG. 14G shows a top view of a photodetection device according to an embodiment. FIG. 14H shows a cross-sectional view along line A-A' in FIG. 14G according to an embodiment. FIG. 14I shows a cross-sectional view along line B-B' in FIG. 14G according to an embodiment. The photodetection device 1400g in FIG. 14G is similar to the photodetection device 1400c in FIG. 14C. The differences are described below. The second doped region 108 is in the substrate 20. In other words, the fourth peak doping concentration of the second doped region 108 is located in the substrate 20. In an embodiment, the second doped region 108 is below the first surface 1401 of the protective layer 1400 and is in direct contact with the absorption region 10. For example, the second doped region 108 may be in contact with or overlap with one of the side surfaces 13 of the absorption region 10. As a result, carriers generated from the absorption region 10 can move from the absorption region 10 through the heterointerface between the absorption region 10 and the substrate 20 toward the second doped region 108. The second electrode 60 is on the first surface 1401 of the protective layer 1400.

[0221] FIG. 14J shows a top view of a photodetection device according to an embodiment. FIG. 14K shows a cross-sectional view along line A-A' in FIG. 14J according to an embodiment. FIG. 14L shows a cross-sectional view along line B-B' in FIG. 14J according to an embodiment. The photodetection device 1400j in FIG. 14J is similar to the photodetection device 1400g in FIG. 14G. The differences are described below. In an embodiment, the width of the conduction region 201 is smaller than the distance between the two control electrodes 340a, 340b. The second doped region 108 can surround at least a portion of the absorption region 10. The second doped region 108 can prevent the charge generated by the light in the absorption region 10 from reaching the substrate 20, which increases the collection efficiency of the carriers generated by the light of the photodetection device 1400j. The second doped region 108 can also prevent the charge generated by the light in the substrate 20 from reaching the absorption region 10, which increases the speed of the carriers generated by the light of the photodetection device 1400j. The second doped region 108 can include the same material as the material of the absorption region 10, the same material as the material of the substrate 20, a material that is a combination of the material of the absorption region 10 and the material of the substrate 20, or a material different from the material of the absorption region 10 and the material of the substrate 20. In an embodiment, the shape of the second doped region 108 can be a ring, although it is not limited. In an embodiment, the second doped region 108 can reduce the crosstalk between two adjacent pixels of the photodetection device. In an embodiment, the second doped region 108 extends to reach the first surface 21 of the substrate 20.

[0222] FIG. 15A shows a gain component 1500a with two terminals. The gain component 1500a includes a lightly doped region 1510 (e.g., an n region, e.g., le14~le17cm -3 ) and an emitter region 1520 and a collector region 1530.

[0223] The collector region 1530 is for collecting carriers and is coupled to a collector electrode (C). The collector region 1530 is a heavily p-doped (p++, e.g., le18~le21cm -3) are of a conductive type such as this. The emitter region 1520 is for emitting carriers and is coupled to the emitter electrode (E). The emitter region 1520 is of a conductive type such as heavily p-doped (p++).

[0224] The materials of the lightly doped region 1510, the emitter region 1520, and the collector region 1530 can be silicon, germanium, silicon-germanium, or III-V materials.

[0225] A method for amplifying optical carriers received by the gain component 1500a includes applying a first voltage (e.g., a positive voltage) to the emitter electrode E and applying a second voltage (e.g., ground) to the collector electrode C, whereby a forward bias is created across the pn junction between the emitter region 1520 and the lightly doped region 1510, and a reverse bias is created across the pn junction between the collector region 1530 and the lightly doped region 1510 to collect an electrical signal (e.g., a hole current) from the emitter, receiving a first type of carrier (e.g., electrons from outside the gain component 1500a) in the lightly doped region 1510 to increase the forward bias between the emitter region 1520 and the lightly doped region 1510, and collecting a second type of carrier (e.g., holes) emitted from the emitter region 1520 by the collector region 1530 as an amplified electrical signal (e.g., an amplified hole current).

[0226] As a result, the gain component provides an amplified electrical signal to the collector region based on the received carriers in the lightly doped region, which improves the signal-to-noise ratio.

[0227] FIG. 15B shows another implementation of the gain component 1500b in which the emitter region 1520 is surrounded by a moderately doped region 1540 (e.g., an n+ region, e.g., le16~le19cm -3 )).

[0228] FIG. 15C shows another implementation of the gain component 1500c in which the collector region 1530 is surrounded by a moderately doped region 1540 (e.g., an n+ region, e.g., le16~le19cm -3 ).

[0229] FIG. 15D shows another implementation of the gain component 1500d in which the emitter region 1520 and the collector region 1530 are surrounded by a moderately doped region (e.g., an n+ region, e.g., le16~le19cm -3 ).

[0230] FIG. 16A shows a gain component 1600a with three terminals. The gain component 1600a includes a lightly doped region 1610 (e.g., an n region), an emitter region 1620, a base region 1640, and a collector region 1630.

[0231] The collector region 1630 is for collecting carriers and is coupled to a collector electrode (C). The collector region 1630 is of a conductivity type such as heavily p-doped (p++). The base region 1640 is coupled to a base electrode (B) and is of a conductivity type such as heavily n-doped (n++). The emitter region 1620 is for emitting carriers and is coupled to an emitter electrode (E). The emitter region 1620 is of a conductivity type such as heavily p-doped (p++).

[0232] The materials of the lightly doped region 1610, the emitter region 1620, the base region 1640, and the collector region 1630 can be silicon, germanium, silicon-germanium, or III-V materials.

[0233] A method for amplifying an optical carrier received by a gain component includes establishing a first voltage difference between an emitter electrode E and a base electrode B to form a forward-biased pn junction, establishing a second voltage difference between a collector electrode C and the base electrode B to form a reverse-biased pn junction, receiving carriers of a first type (e.g., electrons from outside the gain component 1600a) in the lightly doped region 1610, increasing the first voltage difference to form another forward-biased pn junction, and collecting carriers of a second type (e.g., holes) emitted from the emitter region 1620 by the collector region 1630 as an amplified electrical signal.

[0234] As a result, the gain component 1600a provides an amplified electrical signal to the collector region 1630 based on the received carriers in the lightly doped region 1610, which improves the signal-to-noise ratio.

[0235] FIG. 16B shows another implementation of the gain component 1600b in which the emitter region 1620 and the base region 1640 are surrounded by a moderately doped region 1650 (e.g., an n+ region).

[0236] FIG. 16C shows another implementation of the gain component 1600c in which the collector region 1630 and the base region 1640 are surrounded by a moderately doped region 1650 (e.g., an n+ region).

[0237] FIG. 16D shows another implementation of the gain component 1600d in which the emitter region 1620, the base region 1640, and the collector region 1630 are surrounded by a moderately doped region 1650 (e.g., an n+ region).

[0238] FIG. 17A shows a CMOS image sensor 1700a (or a light detection device) including a lightly doped region 1710 (e.g., n-Si), an absorption region 1720 (e.g., p-Ge), and a gain component 1730 (e.g., Si). The gain component 1730 can be a two-terminal or three-terminal gain component as described in FIGS. 15A-15D and FIGS. 16A-16D.

[0239] The absorption region 1720 or the lightly doped region 1710 is a semiconductor material including a group III-V semiconductor material (e.g., InGaAs, GaAs / AlAs, InP / InGaAs, GaSb / InAs, or InSb), a semiconductor material including a group IV element (e.g., Ge, Si, or Sn), Si x Ge y Sn 1-x-y (0≦x≦1, 0≦y≦1), Ge 1-a Sn a (0≦a≦0.1), or Ge 1-x Si x It can be a compound such as (0≦x≦0.1).

[0240] In one embodiment, the bandgap of the lightly doped region 1710 (e.g., n-Si) is larger than the bandgap of the absorption region 1720 (e.g., p-Ge). The gain component 1730 is for collecting optical carriers to generate an amplified electrical signal. The absorption region 1720 includes a first dopant having a first peak doping concentration. The lightly doped region 1710 includes a second dopant having a second peak doping concentration smaller than the first peak doping concentration to reduce the dark current of the CMOS image sensor 1700a (e.g., less than 10 pA).

[0241] The first peak doping concentration is 1×10 17 cm -3 to 1×10 20 cm -3It can be between. In certain embodiments, the ratio of the first peak doping concentration to the second peak doping concentration is 10 or greater such that the CMOS image sensor 1700a exhibits low dark current (e.g., 10 pA or less) and high quantum efficiency. The absorption region 1720 can have a graded doping profile, and the first peak doping is far from the interface between the absorption region 1720 and the lightly doped region 1710.

[0242] The absorption region 1720 can include a heavily doped region 1722 (e.g., p++) coupled to a voltage (e.g., ground). The lightly doped region 1710 can receive optical carriers of a first type (e.g., electrons), and the heavily doped region 1722 can receive optical carriers of a second type (e.g., holes).

[0243] A method for amplifying optical carriers received by a gain component 1730 includes receiving an optical signal in an absorption region 1720 (e.g., p-Ge) to generate optical carriers having a first type and a second type (e.g., electrons and holes), steering optical carriers of the first type (e.g., electrons) to the gain region 1730, and generating an amplified electrical signal having a second type (e.g., holes).

[0244] Thereby, the CMOS image sensor 1700a provides an amplified electrical signal based on the optical signal, improving the signal-to-noise ratio.

[0245] In certain implementations, the light absorption region can be covered by a different material 1750 (e.g., poly-Si) (as indicated by the dashed line).

[0246] FIG. 17B shows an implementation of a CMOS sensor 1700b, where the light absorption region 1720 is partially embedded in the lightly doped region 1710.

[0247] FIG. 17C shows an implementation of a CMOS sensor 1700c, where the light absorption region 1720 is fully embedded in the lightly doped region 1710.

[0248] Similar to FIG. 17A, FIG. 18A shows a CMOS image sensor 1800a including a lightly doped region 1810 (e.g., n-Si), an absorption region 1820 (e.g., p-Ge), and a gain component 1830 (e.g., Si). The gain component 1830 can be a two-terminal or three-terminal gain component as described in FIGS. 15A-15D and FIGS. 16A-16D.

[0249] The lightly doped region 1810 may include a heavily doped region 1822 (e.g., p++) coupled to a voltage (e.g., ground). The lightly doped region 1810 can receive both a first type of optical carrier (e.g., electrons) and a second type of optical carrier (e.g., holes). While the first type of optical carrier is directed towards the gain component 1830, the second type of optical carrier is collected by the heavily doped region 1822.

[0250] A method for amplifying optical carriers received by the gain component 1830 includes receiving an optical signal in the absorption region 1820 (e.g., p-Ge) to generate optical carriers having a first type and a second type (e.g., electrons and holes), steering the first type of optical carrier (e.g., electrons) towards the gain region 1830, and generating an amplified electrical signal having a second type (e.g., holes).

[0251] Thereby, the CMOS image sensor 1800a provides an amplified electrical signal based on the optical signal, improving the signal-to-noise ratio.

[0252] In one implementation, the light absorption region 1820 can be covered by a different material (e.g., poly-Si) (as shown by the dotted line).

[0253] FIG. 18B shows an implementation of the CMOS sensor 1800b, where the light absorption region is partially embedded in the lightly doped region 1810.

[0254] FIG. 18C shows an implementation of the CMOS sensor 1800c, where the light absorption region is completely embedded in the lightly doped region 1810.

[0255] FIG. 19A shows a photodetection device 1900a with gain. The photodetection device 1900a includes a lightly doped region 1910 (e.g., n-Si), an absorption region 1920 (e.g., p-Ge), two gain components 1930a and 1930b, and two control regions 1940a and 1940b (shown as p++) each coupled to a control terminal (M1 and M2), which may be undoped or lightly doped. The gain components 1930a, 1930b can be two-terminal or three-terminal gain components as described in FIGS. 15A - 15D and FIGS. 16A - 16D.

[0256] The absorption region 1920 or the lightly doped region 1910 can be a semiconductor material containing a group III - V semiconductor material (e.g., InGaAs, GaAs / AlAs, InP / InGaAs, GaSb / InAs, or InSb), a semiconductor material containing a group IV element (e.g., Ge, Si, or Sn), Si x Ge y Sn 1-x-y (0 ≦ x ≦ 1, 0 ≦ y ≦ 1), or Ge 1-a Sn a (0 ≦ a ≦ 0.1) and the like.

[0257] In one embodiment, the bandgap of the lightly doped region 1910 (e.g., n-Si) is larger than the bandgap of the absorption region 1920 (e.g., p-Ge). The gain components 1930a, 1930b are for collecting optical carriers to generate an amplified electrical signal. The absorption region 1920 includes a first dopant having a first peak doping concentration. The lightly doped region 1910 includes a second dopant having a second peak doping concentration smaller than the first peak doping concentration to reduce the dark current of the photodetection device 1900a (e.g., less than 10 pA).

[0258] The first peak doping concentration and the second peak concentration can be the same as the example described in FIG. 17A.

[0259] Absorption region 1920 may include a heavily doped region 1922 (e.g., p++) coupled to voltage V0 (e.g., ground). The lightly doped region 1910 can receive light carriers of the first type (e.g., electrons), and the heavily doped region 1922 can receive light carriers of the second type (e.g., holes).

[0260] Control signals M1 and M2 can steer light carriers of the first type towards one of gain components 1930a or 1930b.

[0261] A method for amplifying light carriers received by a gain component includes receiving an optical signal in an absorption region 1920 (e.g., p-Ge) to generate light carriers having the first type and the second type (e.g., electrons and holes), steering light carriers of the first type (e.g., electrons) towards gain region 1930a or 1930b, and generating an amplified electrical signal having the second type (e.g., holes).

[0262] Thereby, the optical detection device 1900a provides an amplified electrical signal based on the optical signal, improving the signal-to-noise ratio.

[0263] In one implementation, the light absorption region 1920 may be covered by a different material (e.g., poly Si) (not shown here).

[0264] In one implementation, the light absorption region 1920 may be partially (e.g., similar to absorption region 1720 as shown in FIG. 17B) or completely (e.g., similar to absorption region 1720 as shown in FIG. 17C) embedded in the lightly doped region 1910.

[0265] FIG. 19B shows a photodetector 1900b with gain. The photodetector 1900b is similar to the photodetector 1900a in FIG. 19A, except that a control region is combined with an emitter region so that an emitter signal (E) can be used to steer carriers and to amplify carriers.

[0266] FIG. 20A shows a top view of an example of a photodetector 2000a with gain, such as that described in FIG. 19A or FIG. 19B, where the lightly doped region is the substrate 2010.

[0267] FIG. 20B shows a top view of an example of a photodetector 2000b with gain, such as that described in FIG. 19A or FIG. 19B, where the substrate 2010 can be intrinsic (e.g., i-Si), lightly p-doped (p-Si), or lightly n-doped (n-Si). A lightly doped region 2012 (e.g., n-Si) can be formed on the substrate 2010 by implantation, diffusion, or other suitable fabrication methods. In one implementation, a portion of the absorption region 2020 (e.g., p-Ge) can be formed in a region of the substrate 2010 that is not the lightly doped region 2012. The absorption region 2020 can be coupled to the lightly doped region 2012 through a lightly doped path 2030 (e.g., n-Si) formed between the absorption region 2020 and the substrate 2010. Photo carriers (e.g., electrons) generated by the absorption region 2020 can drift from the absorption region 2020 to the lightly doped region 2012, so that one of the gain components can generate an amplified electrical signal based on a control signal. Thus, the photodetector 2000b can be formed on a substrate that is intrinsic, lightly p-doped, or lightly n-doped.

[0268] FIG. 21 shows a photodetector 2100a with gain. The photodetector 2100a includes a lightly doped region 2110 (e.g., n-Si), an absorption region 2120 (e.g., p-Ge), two gain components 2130a and 2130b, and two control regions 2140a and 2140b (shown as p++) each coupled to a control terminal (M1 and M2), which are formed on a substrate 2150 (e.g., n-Si, p-Si, or intrinsic Si). The gain components 2130a, 2130b can be two-terminal or three-terminal gain components as described in FIGS. 15A-15D and FIGS. 16A-16D.

[0269] Thus, the photodetector 2100a can be formed on the substrate 2150 with intrinsic, lightly p-doped, or lightly n-doped.

[0270] The absorption region 2120 or the lightly doped region 2110 can be formed using a material as described in FIG. 19A.

[0271] In some embodiments, the lightly doped region 2110 can partially or completely overlap the two control regions 2140a and 2140b.

[0272] The absorption region can include a heavily doped region 2122 (e.g., p++) coupled to a voltage V0 (e.g., ground). The lightly doped region 2110 can receive a first type of optical carrier (e.g., electrons), and the heavily doped region 2122 can receive a second type of optical carrier (e.g., holes).

[0273] The control signals M1 and M2 direct a first type of optical carrier towards one of the gain components 2130a or 2130b as described with reference to FIG. 19A.

[0274] In some implementations, the light absorption region 2120 can be covered by a different material (e.g., poly-Si) (not shown here).

[0275] In one implementation, the light absorption region 2120 can be partially (e.g., similar to the absorption region 1720 as shown in FIG. 17B) or fully (e.g., similar to the absorption region 1720 as shown in FIG. 17C) embedded in the lightly doped region 2110.

[0276] In one implementation, similar to FIG. 19B, the control regions 2140a and 2140b can be combined with the emitter region so that the emitter signal (E) can be used to steer the carrier and to amplify the carrier.

[0277] FIG. 22A shows a top view of an example of a gain-enabled photodetector 2200a, such as the photodetector 2100a described in FIG. 21, and FIG. 22B shows a top view of an example of a gain-enabled photodetector 2200b, such as the photodetector 2100a described in FIG. 21. A portion of the absorption region 2120 (e.g., p-Ge) can be formed in a region of the substrate 2150 that is not the lightly doped region 2110. The lightly doped region 2110 (e.g., n-Si) can be formed in the substrate 2150 by implantation, diffusion, or other suitable fabrication methods. The absorption region 2120 can be coupled to the lightly doped region 2110 through a lightly doped path 2230 (e.g., n-Si) formed between the absorption region 2120 and the substrate 2150. Photo carriers (e.g., electrons) generated by the absorption region 2120 can drift from the absorption region 2120 to the lightly doped region 2110, so that one of the gain components can generate an amplified electrical signal (e.g., hole current) based on a control signal.

[0278] FIG. 23A shows a top view of an example of an optical detection device 2300a with gain. Similar to FIGS. 18A - 18C, a heavily doped region 2322 (e.g., p++) is formed in a lightly doped region 2310 (e.g., n - Si) instead of an absorption region 2320 (e.g., p - Ge). The lightly doped region 2310 can receive both a first type of optical carrier (e.g., electrons) and a second type of optical carrier (e.g., holes). While the first type of optical carrier is directed towards a gain component 2330a or 2330b based on a control signal 2340a or 2340b, the second type of optical carrier is collected by the heavily doped region 2322.

[0279] FIG. 23B shows a top view of another example of an optical detection device 2300b with gain, which is similar to FIG. 23A. However, a portion of the absorption region 2320 (e.g., p - Ge) can be formed in a region of a substrate 2312 that is not the lightly doped region 2310. The absorption region 2320 can be coupled to the lightly doped region 2310 through a lightly doped path 2350 (e.g., n - Si) formed between the absorption region 2320 and the substrate 2312. Optical carriers (e.g., electrons) generated by the absorption region 2320 can drift from the absorption region 2320 to the lightly doped region 2310. Therefore, one of the gain components 2330a or 2330b can generate an amplified electrical signal (e.g., hole current) based on a control signal 2340a or 2340b.

[0280] FIG. 24A shows a top view of an example of a gain - associated optical detection device 2400a, which is similar to FIG. 22A, but a heavily doped region 2422 (e.g., p++) is formed outside the light - absorbing region 2420 (e.g., p - Ge) (similar to that shown in FIGS. 18A - 18C). A portion of the absorption region 2420 (e.g., p - Ge) may be formed in a region of the substrate 2450 that is not the lightly doped region 2410. The lightly doped region 2410 can partially overlap with two control regions 2440a and 2440b (e.g., p++) adjacent to the gain components 2430a and 2430b. Optical carriers (e.g., electrons) generated by the absorption region 2420 can drift from the absorption region 2420 to the lightly doped region 2410, so that one of the gain components 2430a or 2430b can generate an amplified electrical signal (e.g., hole current) based on a control signal.

[0281] FIG. 24B shows a top view of another example of a gain - associated optical detection device 2400b, which is similar to FIG. 22B, but a heavily doped region 2422 (e.g., p++) is formed outside the light - absorbing region 2420 (e.g., p - Ge) (similar to that shown in FIGS. 18A - 18C). The absorption region 2420 can be coupled to the lightly doped region 2410 through a lightly doped path 2460 (e.g., n - Si) formed between the absorption region 2420 and the substrate 2450. Optical carriers (e.g., electrons) generated by the absorption region 2420 can drift from the absorption region 2420 to the lightly doped region 2410, so that one of the gain components 2430a or 2430b can generate an amplified electrical signal (e.g., hole current) based on the control signals 2440a and 2440b.

[0282] Figs. 25A to 25C show cross-sectional views of a part of a photodetection device according to an embodiment. The photodetection device may have substantially the same structure as any of the embodiments described above. In one embodiment, when not explicitly mentioned in the above description, referring to Fig. 25A, the absorption region 10 may be entirely on the first surface 21 of the substrate 20. Referring to Fig. 25B, the absorption region 10 may be partially embedded in the substrate 20. That is, a part of each side surface is in contact with the substrate 20. Referring to Fig. 25C, the absorption region 10 may be entirely embedded in the substrate 20. That is, the side surface is in contact with the substrate 20.

[0283] Figs. 26A to 26D show examples of control regions C1, C2, C3, C4 of a photodetection device according to an embodiment. The photodetection device may have substantially the same structure as any of the embodiments described above.

[0284] Referring to Fig. 26A, in one embodiment, the control electrode 340 may be on the first surface 21 of the substrate 20 where the intrinsic region is directly below the control electrode 340. The control electrode 340 may result in the formation of a Schottky contact, a resistive contact, or a combination having intermediate characteristics between the two, depending on various factors including the material of the substrate 20, or the protective layer, and / or the material of the control electrode 340, and / or the dopant or defect level of the substrate 20 or the protective layer 1400. The control electrode 340 may be any one of the control electrodes 340a, 340b, 340c, 340d.

[0285] Referring to Fig. 26B, in one embodiment, the control region of the switch further includes a doped region 303 in the substrate 20 under the control electrode 340. In one embodiment, the doped region 303 has a conductivity type different from that of the first doped regions 302a, 302b. In one embodiment, the doped region 303 includes a dopant and a dopant profile. The peak dopant concentration of the doped region 303 depends on the material of the control electrode 340, and / or the material of the substrate 20, and / or the dopant or defect level of the substrate 20, and is, for example, 1×10 17 cm-3 to 5×10 20 cm -3 therebetween. The doped region 303 forms a Schottky contact, a resistive contact, or a combination thereof with the control electrode 340. The doped region is for demodulating carriers generated from the absorption region 10 based on the control of a control signal. The control electrode 340 can be any one of control electrodes 340a, 340b, 340c, and 340d.

[0286] Referring to FIG. 26C, in one embodiment, the control region of the switch further includes a dielectric layer 350 between the substrate 20 and the control electrode 340. The dielectric layer 350 prevents direct current conduction from the control electrode 340 to the substrate 20, but can establish an electric field in the substrate 20 in response to the application of a voltage to the control electrode 340. For example, an established electric field between two of the control regions, such as between control regions C1 and C2, can attract or repel charge carriers in the substrate 20. The control electrode 340 can be any one of control electrodes 340a, 340b, 340c, and 340d.

[0287] Referring to FIG. 26D, in one embodiment, the control region of the switch further includes a doped region 303 in the substrate 20 under the control electrode 340, and also includes a dielectric layer 350 between the substrate 20 and the control electrode 340. The control electrode 340 can be any one of control electrodes 340a, 340b, 340c, and 340d.

[0288] In one embodiment, the region of the carrier conduction layer directly under the readout electrode can be intrinsic. For example, the region of the substrate directly under each readout electrode of the switch can be intrinsic. For other examples, the region of the protective layer directly under each readout electrode of the switch can be intrinsic. The readout electrode can result in the formation of a Schottky contact, a resistive contact, or a combination having intermediate characteristics between the two, depending on various factors including the material of the substrate 20, or the material of the protective layer 1400, or the material of the protective layer, and / or the material of the readout electrode, and / or the dopant or defect level of the substrate 20 or the protective layer 1400.

[0289] In some embodiments, the dielectric layer 350 may include, but is not limited to, SiO2. In some embodiments, the dielectric layer 350 may include, but is not limited to, Si3N4, SiON, SiN x , SiO x , GeO x , a high-k material including Al2O3, Y2O3, TiO2, HfO2, or ZrO2. In some embodiments, the dielectric layer 350 may include, but is not limited to, a semiconductor material such as amorphous Si, polycrystalline Si, crystalline Si, germanium-silicon, or a combination thereof.

[0290] In some embodiments, the conductive region 201 of the photodetector device can be of any suitable design. By way of example, referring to the conductive region 201 of the photodetector device in FIGS. 3A-3B, FIGS. 4A-4C, FIGS. 5A-5C, FIGS. 6A-6G, FIGS. 7A-7E, FIGS. 8A-8E, FIGS. 14C-14L, the width of the conductive region 201 can be made smaller than the distance between the control electrodes 340a, 340b. In some embodiments, the conductive region 201 may not overlap with any part of the two doped regions 303 described in FIGS. 26B and 26D. In some embodiments, the conductive region 201 may overlap with a part of the two doped regions 303 described in FIGS. 26B and 26D. In some embodiments, the conductive region 201 may overlap with the entire doped region 303 described in FIGS. 26B and 26D. In some embodiments, the conductive region 201 may not overlap with any part of each of the first doped regions 302a, 302b. In some embodiments, the conductive region 201 may overlap with a part of each of the first doped regions 302a, 302b. In some embodiments, the conductive region 201 may overlap with the entire first doped regions 302a, 302b.

[0291] As another example, referring to the conductive region 201 of the photodetection device in FIGS. 10A and 11A, the conductive region 201 may not overlap with any part of the third contact region 208. In certain embodiments, the conductive region 201 may overlap with a portion of the third contact region 208. In certain embodiments, the conductive region 201 may overlap with the entire third contact region 208. In certain embodiments, the conductive region 201 may not overlap with any part of the first contact region 204. In certain embodiments, the conductive region 201 may overlap with a portion of the first contact region 204. In certain embodiments, the conductive region 201 may overlap with the entire first contact region 204.

[0292] As another example, referring to the conductive region 201 of the photodetection device in FIGS. 1A - 1D and FIGS. 2A - 2F, the conductive region 201 may not overlap with any part of the first doped region 102. In certain embodiments, the conductive region 201 may overlap with a portion of the first doped region 102. In certain embodiments, the conductive region 201 may overlap with the entire first doped region 102.

[0293] In certain embodiments, any of the previously mentioned photodetection devices, such as the photodetection devices in FIGS. 1A - 11E, FIGS. 13 - 26D, may include a waveguide similar to the waveguide 206 described in FIGS. 12A - 12C to guide and / or restrict an incident optical signal passing through a defined region of the substrate 20. FIG. 27A is a block diagram of an example embodiment of an imaging system. The imaging system may include an imaging module and a software module configured to reconstruct a three - dimensional model of a detected object. The imaging system or the imaging module may be implemented in a mobile device (e.g., a smartphone, a tablet, a vehicle, a drone, etc.), an accessory device for a mobile device (e.g., a wearable device), a computer system in a vehicle and a fixed facility (e.g., a factory), a robotic system, a monitoring system, or any other suitable device and / or system.

[0294] The imaging module includes a transmitting unit, a receiving unit, and a control device. During operation, the transmitting unit can emit emitted light rays towards a target object. The receiving unit can receive reflected light rays reflected from the target object. The control device can drive at least the transmitting unit and the receiving unit. In one implementation, the receiving unit and the control device are implemented in one semiconductor chip such as a system on chip (SoC). In some cases, the transmitting unit is implemented by two different semiconductor chips, such as a laser emitter chip on a III-V substrate and a Si laser driver chip on a Si substrate.

[0295] The transmitting unit may include one or more light sources, a control circuit for controlling one or more light sources, and / or an optical structure for manipulating the light rays emitted from one or more light sources. In one embodiment, the light source may include light rays emitted by one or more LEDs or VCSELs that can be absorbed by an absorption region in a light detection device. For example, one or more LEDs or VCSELs can emit light rays with a peak wavelength within the visible wavelength range (e.g., a wavelength visible to the human eye), such as 570 nm, 670 nm, or any other applicable wavelength. For other examples, one or more LEDs or VCSELs can emit light rays with a peak wavelength beyond the visible wavelength range, such as 850 nm, 940 nm, 1050 nm, 1064 nm, 1310 nm, 1350 nm, 1550 nm, or any other applicable wavelength.

[0296] In one embodiment, the emitted light rays from the light source can be made parallel by one or more optical structures. For example, the optical structure may include one or more collimating lenses.

[0297] The receiving unit may comprise one or more light detection devices according to any of the embodiments mentioned above. The receiving unit may further comprise a control circuit for controlling the control circuit and / or an optical structure for directing the light rays reflected from the target object towards the one or more light detection devices. In one implementation, the optical structure comprises one or more lenses that receive parallel light rays and focus the parallel light rays towards the one or more light detection devices.

[0298] In one embodiment, the control device comprises a timing generator and a processing unit. The timing generator receives a reference clock signal and provides a timing signal to the transmitting unit for modulating the emitted light rays. The timing signal is also provided to the receiving unit for controlling the collection of the optical carriers. The processing unit processes the optical carriers generated and collected by the receiving unit and determines the raw data of the target object. The processing unit may comprise a control circuit, one or more signal processing devices for processing the information output from the light detection device, and / or a computer storage medium that can store instructions for determining the raw data of the target object or can store the raw data of the target object. As an example, in an i-ToF sensor, the control device determines the distance between two points using the phase difference between the light rays emitted by the transmitting unit and the light rays received by the receiving unit.

[0299] The software module may be implemented for execution in applications such as face authentication, visual target tracking, gesture recognition, three-dimensional model scanning / video recording, motion tracking, autonomous vehicles, and / or augmented / virtual reality.

[0300] FIG. 27B shows a block diagram of an example receiving unit or control device. Here, an image sensor array (e.g., 240×180) can be implemented using any implementation of the photodetection device described with reference to FIGS. 3A-3H, 4A-4H, 5A-5H, 6A-6H, 7A-7H, 8A-8H, 14C-14L. A phase-locked loop (PLL) circuit (e.g., an integer-N PLL) can generate clock signals (e.g., a 4-phase system clock) for modulation and demodulation. These clock signals can be gated and / or conditioned by a timing generator for preset integration times and different operating modes before being sent to the pixel array and an external illumination driver. A programmable delay line can be added to the illumination driver path to delay the clock signal.

[0301] A voltage regulator can be used to control the operating voltage of the image sensor. For example, multiple voltage regions can be used for the image sensor. A temperature sensor can be implemented for possible use in depth calibration and power control.

[0302] The readout circuit of the photodetection device bridges each of the photodetection devices of the image sensor array to a column analog-to-digital converter (ADC), and the ADC output can be further processed and integrated in the digital domain by a signal processing device before reaching the output interface. A storage device can be used to store the output by the signal processing device. In one implementation, the output interface can be implemented using a 2-lane, 1.2 Gb / s D-PHY MIPI transmitter or a CMOS output for a low-speed / low-cost system.

[0303] An I2C interface may be used to access all of the functional blocks described herein.

[0304] In certain embodiments, the light detection device in the present disclosure further includes an optical element (not shown) on the pixel. In certain embodiments, the light detection device in the present disclosure further includes a plurality of optical elements (not shown) on a plurality of pixels. The optical element converges the incoming optical signal in order to direct it into the absorption region. In certain embodiments, the optical element includes a lens.

[0305] In certain embodiments, the p-type dopant includes a Group III element. In certain embodiments, the p-type dopant is boron. In certain embodiments, the n-type dopant includes a Group V element. In certain embodiments, the n-type dopant is phosphorus.

[0306] In the present disclosure, unless explicitly stated otherwise, the absorption region is configured to absorb photons having a peak wavelength in the invisible wavelength range of 800 nm or more, such as 850 nm, 940 nm, 1050 nm, 1064 nm, 1310 nm, 1350 nm, 1550 nm, or any suitable wavelength range. In certain embodiments, the absorption region receives an optical signal and converts the optical signal into an electrical signal. The absorption region can be of any suitable shape, such as a cylinder, a right prism, etc., without being limited thereto.

[0307] In the present disclosure, unless explicitly stated otherwise, the absorption region has a thickness corresponding to the wavelength of the detected photons and the material of the absorption region. In certain embodiments, when the absorption region includes germanium and is designed to absorb photons having a wavelength of 800 nm or more, the absorption region has a thickness of 0.1 μm or more. In certain embodiments, when the absorption region includes germanium and is designed to absorb photons having a wavelength between 800 nm and 2000 nm, the absorption region has a thickness between 0.1 μm and 2.5 μm. In certain embodiments, the absorption region has a thickness between 1 μm and 2.5 μm for a higher quantum efficiency. In certain embodiments, the absorption region can be grown using blanket epitaxy, selective epitaxy, or other suitable techniques.

[0308] In the present disclosure, unless explicitly stated otherwise, the light shield has an optical window for defining the position of the absorption region within the absorption area. In other words, the optical window is for allowing an incident optical signal to enter the absorption region and for defining the absorption region. In certain embodiments, the light shield is on the second surface of the substrate away from the absorption region when the incident light enters the absorption region from the second surface of the substrate. In certain embodiments, the shape of the optical window can be elliptical, circular, rectangular, square, rhombic, octagonal, or any other suitable shape when viewed from above the optical window.

[0309] In the present disclosure, unless explicitly stated otherwise, the type of carriers collected by the first doped region of one of the switches in the same pixel is the same as the type of carriers collected by the first doped regions of the other switches. For example, when the photodetection device is configured to collect electrons, when the first switch is turned on and the second switch is turned off, the first doped region in the first switch collects the electrons of the optical carriers generated from the absorption region, and when the second switch is turned on and the first switch is turned off, the first doped region in the second switch also collects the electrons of the optical carriers generated from the absorption region.

[0310] In the present disclosure, unless explicitly stated otherwise, the first electrode, the second electrode, the readout electrode, and the control electrode include a metal or an alloy. For example, the first electrode, the second electrode, the readout electrode, and the control electrode include Al, Cu, W, Ti, a Ta-TaN-Cu stack, or a Ti-TiN-W stack.

[0311] In certain embodiments, unless explicitly stated otherwise, the cross-sectional views shown in the present disclosure can be cross-sectional views along any possible cutting line of the photodetection device or the photodetection device.

[0312] As used herein and unless otherwise defined, the terms "substantially" and "about" are used to describe and account for small variations. When used in conjunction with an event or circumstance, the term can cover instances where the event or circumstance occurs exactly as well as instances where the event or circumstance occurs in close approximation. For example, when used in conjunction with a numerical value, the term can cover variations within ±10% of that numerical value, such as within ±5% or less, ±4% or less, ±3% or less, ±2% or less, ±1% or less, ±0.5% or less, ±0.1% or less, or ±0.05% or less.

[0313] Although the present disclosure has been described from the perspective of preferred embodiments using examples, it is understood that the present disclosure is not limited thereto. On the contrary, it is intended to cover various modifications as well as similar configurations and procedures, and therefore, the scope of the appended claims should be given the broadest interpretation so as to cover all such modifications as well as similar configurations and procedures.

[0314] Those skilled in the art will readily notice that they can make numerous changes and modifications to the devices and methods while retaining the teachings of the present disclosure. Therefore, the above disclosure should be construed as being limited only by the scope and boundaries of the appended claims.

Explanation of Reference Numerals

[0315] 10 Absorbing region 11 First surface 12 Second surface 13 Side surface 20 Substrate 20a Base portion 20b Upper portion 20c Intermediate portion 21 First surface 22 Second surface 30 First electrode 40 Third electrode 60 Second electrode, third electrode 60a, 60b, 60c, 60d Sub - electrodes 100a, 100b, 100c, 100d, 200a, 200b, 200c, 200d, 300a, 400a, 500a, 600a, 600c, 600f, 600g, 700a, 700c, 700d, 700e, 800a, 800c, 800d, 800e, 1000a, 1000b, 1000d, 1000g, 1000h, 1000i, 1100a, 1100b, 1100d, 1200a, 1200b, 1200c, 1300a, 1300b, 1400c, 1400f, 1400g, 1400j Photodetector devices 102, 104 First doped region 103 Second contact region 108 Second doped region 108a, 108b, 108c, 108d Small regions 130 Third electrode 130A Voltage control transistor 140 First electrode 141A Reset transistor 142A Source follower 143A Row selection transistor 150A Capacitor 160 Second electrode 171A Transfer transistor 180 Limiting region 181 Passageway 200e, 200f Photodetector 201 Conductive region 202 Charge layer 203 Correction element 204 First contact region 205 Recess 206 Waveguide, ridge, trench 208 Third contact region 210 Intermediate doped region 212 Lower doped region 302a, 302b First doped region 303 Doped region 330a, 330b, 330c, 330d, 330e, 330f, 330g, 330h Readout electrodes Control electrodes 340, 340a, 340b, 340c, 340d, 340e, 340f, 340g, 340h Dielectric layer 350 Photodetection devices 900a, 900b Collector region 1302 Emitter region 1304 Base contact region 1308 First electrode 1330 Second electrode 1340 Third electrode 1360 Protection layer 1400 First surface 1401 Gain components 1500a, 1500b, 1500c, 1500d Lightly doped region 1510 Emitter region 1520 Collector region 1530 Moderately doped region 1540 Gain components 1600a, 1600b, 1600c, 1600d Lightly doped region 1610 Emitter region 1620 Collector region 1630 Base region 1640 Moderately doped region 1650 CMOS image sensors 1700a, 1700b, 1700c, 1800a, 1800b, 1800c Lightly doped regions 1710, 1810 Absorption regions 1720, 1820 Heavily doped regions 1722, 1822 Gain components, gain regions 1730, 1830 Material 1750 Photodetection devices 1900a, 1900b Lightly doped region 1910 Absorption region 1920 Heavily doped region 1922 Gain components, gain regions 1930a, 1930b Control regions 1940a, 1940b Photodetection devices 2000a, 2000b 2010 Substrate 2020 Absorption Region 2030 Mild Doping Path 2100a Photo-Detection Device 2110 Mild Doping Region 2130a, 2130b Gain Components 2140a, 2140b Control Region 2150 Substrate 2300a Photo-Detection Device 2310 Mild Doping Region 2312 Substrate 2320 Absorption Region 2322 Heavy Doping Region 2330a, 2330b Gain Components 2340a, 2340b Control Signal 2400a, 2400b Photo-Detection Device 2410 Mild Doping Region 2420 Light Absorption Region 2422 Heavy Doping Region 2430a, 2430b Gain Components 2440a, 2440b Control Region, Control Signal 2450 Substrate 2460 Mild Doping Path AR Absorption Region B Base Electrode C Collector Electrode C1, C2, C3, C4 Control Region d Shortest Distance between the First Electrode 30 and the Side Surface 13, Distance between the First Electrode 30 and the Side Surface 13 D1 Direction Substantially Perpendicular to the First Surface 21 E Emitter Electrode, Emitter Signal IA1 Photoelectric Current M Multiplication Region M1, M2 Control Terminals, Control Signal TG1 Switching Signal VA1 Fixed Voltage VC1 Control Voltage VOUT1 Output Voltage V0 Voltage w1 Width of the Absorption Region 10 Width of the second doped region 108 of w2 Y direction

Claims

1. An optical sensor comprising: An absorption region containing p-doped germanium, configured to receive an optical signal and generate optical carriers in response to the optical signal; A silicon substrate in contact with the absorption region via a heterointerface; A first photodetector element including the above; Wherein the silicon substrate comprises: A plurality of p-doped regions; A plurality of n-doped regions, wherein the plurality of p-doped regions are formed closer to the heterointerface than the plurality of n-doped regions; One or more multiplication regions formed between the plurality of p-doped regions and the plurality of n-doped regions, configured to amplify a part of the optical carriers drifting from the absorption region to the plurality of p-doped regions; The silicon substrate includes a second dopant having a second peak doping concentration lower than the first peak doping concentration of the absorption region; An optical sensor, wherein the plurality of p-doped regions and the plurality of n-doped regions are arranged in a staggered pattern.

2. The optical sensor according to claim 1, wherein the silicon substrate further includes an n-doped carrier conduction region in contact with the absorption region for forming the heterointerface.

3. The optical sensor according to claim 2, wherein the plurality of p-doped regions are at least partially overlapped with the n-doped carrier conduction region.

4. The optical sensor according to claim 2, wherein the ratio of the first doping concentration of the absorption region to the second doping concentration of the n-doped carrier conduction region at the heterointerface is 10 or more.

5. The absorption region further includes a first p-doped contact region coupled to a first electrode, the plurality of n-doped regions are coupled to a second electrode, and the first p-doped contact region has a third doping concentration higher than the first doping concentration. The optical sensor according to claim 4.

6. The optical sensor according to claim 5, wherein the plurality of p-doped regions have a fourth doping concentration higher than the second doping concentration of the n-doped carrier conduction region.

7. The optical sensor according to claim 5, wherein the first photodetector element is configured to operate in Geiger mode under a reverse bias between the first electrode and the second electrode.

8. The optical sensor according to claim 5, wherein the plurality of p-doped regions are coupled to a third electrode. **Claim 9**: An optical sensor, an absorption region containing p-doped germanium, configured to receive an optical signal and generate optical carriers in response to the optical signal; a silicon substrate in contact with the absorption region via a heterointerface; comprising a first photodetector element including; wherein the silicon substrate, a plurality of p-doped regions; a plurality of n-doped regions, wherein the plurality of p-doped regions are formed closer to the heterointerface than the plurality of n-doped regions; one or more multiplication regions formed between the plurality of p-doped regions and the plurality of n-doped regions, configured to amplify a portion of the optical carriers drifting from the absorption region to the plurality of p-doped regions; the silicon substrate includes a second dopant having a second peak doping concentration lower than a first peak doping concentration of the absorption region; the silicon substrate further includes an n-doped carrier conduction region in contact with the absorption region to form the heterointerface; an optical sensor, wherein a maximum distance between two outermost p-doped regions of the plurality of p-doped regions is greater than a width of the n-doped carrier conduction region. **Claim 10**: An optical sensor, an absorption region containing p-doped germanium, configured to receive an optical signal and generate optical carriers in response to the optical signal; a silicon substrate in contact with the absorption region via a heterointerface; comprising a first photodetector element including; wherein the silicon substrate, a plurality of p-doped regions; a plurality of n-doped regions, wherein the plurality of p-doped regions are formed closer to the heterointerface than the plurality of n-doped regions; one or more multiplication regions formed between the plurality of p-doped regions and the plurality of n-doped regions, configured to amplify a portion of the optical carriers drifting from the absorption region to the plurality of p-doped regions; the silicon substrate includes a second dopant having a second peak doping concentration lower than a first peak doping concentration of the absorption region; an optical sensor, wherein the absorption region is doped with a stepped doping profile.

11. The optical sensor according to claim 1, wherein the absorption region is at least partially embedded in the silicon substrate.

12. The silicon substrate includes a first surface and a second surface opposite to the first surface, the plurality of p-doped regions are formed closer to the first surface than the plurality of n-doped regions, The optical sensor according to claim 1, wherein the first photodetector further includes one or more optical structures formed on the second surface configured to receive the optical signal.

13. The optical sensor according to claim 12, wherein the one or more optical structures include one or more lenses.

14. The optical sensor according to claim 1, including a sensor array including a one-dimensional (1D) array or a two-dimensional (2D) array of photodetectors formed on the silicon substrate, wherein the 1D array or the 2D array of the photodetectors includes the first photodetector.

15. The optical sensor according to claim 1, wherein the thickness of the one or more multiplication regions ranges from 100 nm to 500 nm.

16. At least 50% of the absorption region is doped at a doping concentration of 1×10 １６ cm －３ or higher, the optical sensor according to claim 1.

17. An optical transmitter configured to emit an optical signal having a peak wavelength greater than 900 nm, an optical sensor, A system comprising: wherein the optical sensor is an absorption region including p-doped gallium, configured to receive the optical signal and generate optical carriers in response to the optical signal, a silicon substrate in contact with the absorption region via a heterointerface, including a first photodetector including wherein the silicon substrate a plurality of p-doped regions, a plurality of n-doped regions, wherein the plurality of p-doped regions are formed closer to the heterointerface than the plurality of n-doped regions, one or more multiplication regions formed between the plurality of p-doped regions and the plurality of n-doped regions, configured to amplify a part of the optical carriers drifting from the absorption region to the plurality of p-doped regions, The silicon substrate includes a second dopant having a second peak doping concentration lower than the first peak doping concentration of the absorption region, the plurality of p-doped regions and the plurality of n-doped regions are arranged in a staggered pattern, system.

18. The system according to claim 17, which is a mobile device, a wearable device, or a robotic device.

19. The system according to claim 17, wherein the optical transmitter includes one or more light-emitting diodes or one or more vertical cavity surface-emitting lasers.

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