Light Detector

Abstract

A photodetector device includes an n-type light absorption region (15n) and a p-type light absorption region (15p) arranged to form a pn junction, and an n+ contact region (n+) and a p+ contact region (p+) connected to corresponding contacts (VI, V2). The light absorption region and the contact region are arranged in an n+pn p+ sequence, so that after the voltage applied between the n+ contact and the p+ contact is switched from reverse bias to forward bias, the electrons and holes generated in the light absorption region in response to photon absorption drift toward the p+ contact region and the n+ contact region, respectively, which causes a current to start flowing between the contacts after a time delay inversely proportional to the incident light intensity.

Description

Technical Field

[0001] The present disclosure relates to a light detector. Background Art

[0002] Conventional pn or pin photodetectors operate by being held at a constant reverse bias voltage. Incident photons are absorbed in the light absorption region to generate electron-hole pairs, which are swept to the contacts so that the magnitude of the photocurrent is proportional to the intensity of the light incident on the photodiode.

[0003] In US 2012 / 313155 A1, a non-conventional type of photodetector is disclosed which operates using a pulsed voltage that switches from reverse bias to forward bias. The switch to forward bias induces a photocurrent to flow across the device structure. However, the start of the flow of photocurrent is not instantaneous, but occurs after a certain time delay from the incident light. This time delay is called the trigger time. The trigger time is proportional to the inverse of the light intensity, so the trigger time is used as a measure of the intensity of the incident light.

[0004] Figure 1A and Figure 1B Schematic representations in cross-section and plan view of a photodetector 1 as disclosed in US 2012 / 313155 A1, respectively. The growth direction (i.e. the direction orthogonal to the plane of the wafer) is marked as the z-direction. The first gate G1 and the second gate G2, which are maintained at voltages VG1 and VG2, extend in the y-direction. The direction orthogonal to the gates in which electrons and holes are swept out is the x-direction. Figure 1A The section AA is as follows Figure 1BIn the indicated xz plane. The gates G1, G2 are arranged on either side of the light absorbing layer 15, the central portion of which is open to receive incident photons. The light absorbing layer 15 can be an intrinsic semiconductor or a doped semiconductor, such as silicon or germanium suitable for absorbing incoming photons in the wavelength range to be detected. Highly doped n+ and p+ regions are arranged on either side of the body region 15 beyond the gate and serve as output terminals for reading out optical signals. The layers of the photodetector 1 are epitaxially fabricated on a semiconductor-on-insulator (SOI) substrate 3 including a silicon wafer and a buffer layer 7, on which an insulator layer 8 is deposited. The gates G1, G2 are made of a conductive material (e.g., a metal, a silicide, or a semiconductor). The gates G1, G2 are separated from the light absorbing layer 15 via an insulator or dielectric material 4 (e.g., silicon oxide or silicon nitride). The photodetector 1 is operated with the following bias voltages. A negative voltage VG1 is applied to the gate G1 (e.g., -2V), a negative voltage or zero voltage V1 is applied to the n+ region, a positive voltage VG2 is applied to the gate G2 (e.g., 2V) and a positive voltage V2 is applied to the p+ region (e.g., 1V). The triggering time of the photodetector is a function of the electric field in the light absorbing layer 15 and can therefore be tuned by adjusting the gate voltage. Under these bias conditions, photons incident on the light absorbing region 15 between the gates, for example from the optical fiber device 30, are absorbed, thereby generating electron-hole pairs, which are then swept out by the electric field induced by the bias voltage, so they are detected as current flowing between the n+ region and the p+ region. Summary of the invention

[0005] According to one aspect of the present disclosure, a photodetector device is provided, which includes: a first light absorption region and a second light absorption region, the first light absorption region and the second light absorption region are composed of semiconductor materials and are n-type and p-type doped, respectively, and the light absorption region is configured to generate electron and hole pairs in response to the absorption of photons when light is incident on the device; a first contact region and a second contact region, the first contact region and the second contact region are composed of semiconductor materials and are p-type and n-type doped, respectively, wherein the contact region has a higher doping concentration than the light absorption region and is marked as p+ and n+, respectively; and a first contact and a second contact, the first contact and the second contact are connected to the first contact region and the second contact region, respectively. The n-type light absorption region and the p-type light absorption region and the n+ contact region and the p+ contact region are arranged in an n+pn p+ order, so that after the voltage applied between the n+ contact and the p+ contact is switched from reverse bias to forward bias, the electrons and holes generated in the light absorption region in response to photon absorption drift toward the p+ contact region and the n+ contact region, respectively, which causes current to begin to flow between the contacts after a time delay inversely proportional to the intensity of the incident light.

[0006] In some embodiments, the first light absorption region and the second light absorption region are arranged side by side relative to the substrate.The first contact region and the second contact region may be arranged to be laterally spaced apart on either side of the first light absorption region and the second light absorption region.

[0007] In some embodiments, the first light absorption region and the second light absorption region are formed as corresponding epitaxial layers arranged on top of each other relative to the substrate. The device may also include an insulating trench extending vertically through the structure to define an array of photodetectors of pixels. The trench extends through the light absorption region and at least one of the contact regions so as to subdivide the photodetector into an array of independently contacted pixels, so that it can be read out individually by suitable electronic instruments. The photodetector may also include, for example, a semiconductor circuit layer arranged on the epitaxial layer forming one of the first contact region and the second contact region in silicon CMOS technology, the semiconductor circuit layer including an array of readout sensors for the pixel array of the photodetector electrically connected to the pixel using a via. In the refinement of the photodetector array, the pixels are each subdivided into an array of sub-pixels by additional insulating trenches. Additional trenches for each pixel are laterally arranged inside the insulating trenches defining the pixel. Additional trenches extend vertically through one of the contact regions and at least one of the light absorption regions in the contact region, but not as far as another contact region in the contact region, so that the sub-pixels of any one pixel remain in common contact, so any group of sub-pixels is biased and read out as a single pixel unit.

[0008] In some embodiments, the first light absorption region and the second light absorption region are arranged such that one of the first light absorption region and the second light absorption region is formed as an epitaxial layer on a substrate, or is formed integrally with the substrate, and the other of the first light absorption region and the second light absorption region is formed as an embedded region within the epitaxial layer.

[0009] In some embodiments, the first light absorption region and the second light absorption region are arranged so that one of the first light absorption region and the second light absorption region is formed in the first part as an epitaxial layer on the substrate or integrally with the substrate, and is formed in the second part as an embedded region within the epitaxial layer or the substrate, and wherein the other of the first light absorption region and the second light absorption region is formed as an additional embedded region within the epitaxial layer. The embedded region and the additional embedded region may be laterally separated by a portion of the epitaxial layer or the substrate. One of the first contact region and the second contact region may be formed as a further embedded region within the embedded region of the first light absorption region or the second light absorption region, respectively. The first contact region and the second contact region may be formed as corresponding further embedded regions within the embedded region of the first light absorption region and the second light absorption region, respectively.

[0010] In some embodiments, one of the first and second contact regions is formed as an epitaxial layer on a substrate, and at least one of the first and second light absorption regions is at least partially formed as an additional epitaxial layer on the epitaxial layer of the one of the first and second contact regions.

[0011] In some embodiments, at least one of the first contact region and the second contact region is respectively formed as an embedded region within an epitaxial layer that forms at least a portion of the first light absorbing region and the second light absorbing region.

[0012] In some embodiments, the first and second contact regions are formed as respective laterally spaced first and second embedded regions within an epitaxial layer that forms at least a portion of the first and second light absorbing regions.

[0013] In some embodiments, one of the first and second contact regions are formed as laterally spaced first and second embedded regions, respectively, formed within an epitaxial layer that forms at least a portion of one of the first and second light absorbing regions.

[0014] It should be understood that the semiconductor material of which the light absorption region is made is selected with attention to its band gap so that the interband absorption of photons occurs over the desired energy range as required by the photodetector to meet the specifications. The semiconductor material of the two light absorption regions can be the same, so that the pn junction between the p-type region and the n-type region is a homojunction, or two different semiconductor materials can be selected so that the pn junction is a heterojunction. In the case of a heterojunction, the two different materials can be in the same material system, so they can form an alloy with each other, such as a SiGeC material system or a GaAlInAsP material system.

[0015] According to another aspect of the present disclosure, there is provided a method for manufacturing a photodetector device, the method comprising: fabricating a first light absorption region and a second light absorption region composed of a semiconductor material and doped with n-type and p-type, respectively, the light absorption region being configured to generate electron and hole pairs in response to absorption of photons when light is incident on the device; fabricating a first contact region and a second contact region composed of a semiconductor material and doped with p-type and n-type, respectively, wherein the contact region has a higher doping concentration than the light absorption region and is labeled as p+ and n+, respectively; and providing a first contact and a second contact connected to the first contact region and the second contact region, respectively. The n-type light absorption region and the p-type light absorption region and the n+ contact region and the p+ contact region are arranged in an n+pn p+ sequence, so that after switching a voltage applied between the n+ contact and the p+ contact from a reverse bias to a forward bias, the electrons and holes generated in the light absorption region in response to absorption of photons drift toward the p+ contact region and the n+ contact region, respectively, which causes a current to begin to flow between the contacts after a time delay inversely proportional to the intensity of the incident light.

[0016] In the above method, the first light absorption region and the second light absorption region can be made as corresponding epitaxial layers arranged on top of each other relative to the substrate. In addition, the method can also include making an insulating trench extending vertically through the light absorption region and at least one of the contact regions so as to subdivide the photodetector into an array of independently contacted pixels. Additional insulating trenches can be provided so that each pixel is subdivided into an array of sub-pixels by additional insulating trenches, and for each pixel, the additional insulating trench is laterally arranged inside the insulating trench defining the pixel and extends vertically through one of the contact regions and at least one of the light absorption regions, but not as far as another of the contact regions, so that the sub-pixels of any one pixel remain in common contact.

[0017] According to another aspect of the present disclosure, there is provided a method of operating a photodetector device as specified above. The method comprises operating the photodetector device by repeating: applying a voltage to reverse bias an n+ contact and a p+ contact; switching the reverse bias voltage to a forward bias voltage such that after said switching, electrons and holes generated in a light absorption region in response to photon absorption drift toward a p+ contact region and an n+ contact region, respectively; and sensing the start of current flow between a first contact and a second contact. A time delay between said switching and said start is measured, the time delay being inversely proportional to the incident light intensity. This reverse to forward bias sequence is then repeated.

[0018] In summary, we propose a photodetector device and a corresponding manufacturing method for the photodetector, the photodetector comprising an n-type light absorption region and a p-type light absorption region arranged to form a pn junction and an n+ contact region and a p+ contact region connected to corresponding contacts. The light absorption region and the contact region are arranged in an n+pn p+ sequence, so that after the voltage applied between the n+ contact and the p+ contact is switched from a reverse bias to a forward bias, the electrons and holes generated in the light absorption region in response to the absorption of photons drift toward the p+ contact region and the n+ contact region, respectively, which causes a current to start flowing between the contacts after a time delay inversely proportional to the intensity of the incident light. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In the following, the invention will be further described, by way of example only, with reference to the exemplary embodiments illustrated in the drawings.

[0020] Figure 1A and Figure 1B Schematic representations in cross-section and plan view, respectively, of a prior art photodetector as disclosed in US 2012 / 313155 A1.

[0021] Figure 2A and Figure 2B Schematic representation in cross-section and in plan view, respectively, of a photodetector according to a first embodiment of the invention.

[0022] Figure 3A , Figure 3B and Figure 3C are energy band diagrams showing the photodetector according to the first embodiment, wherein the photodetector is in a reverse biased state, in a forward biased conducting state, and in a forward biased non-conducting state, respectively.

[0023] Figure 4 is with (“on”) and without (“off”) incident light (i.e. Figure 3C and Figure 3B In the case of forward biased conduction state and non-conduction state) according to Figure 2A and Figure 2B A graph of the output current of the photodetector of the first embodiment as a function of the bias voltage.

[0024] Figure 5A and Figure 5B The voltage V applied in the absence of light and in the presence of light is shown respectively. d and an oscilloscope scope screenshot of the output current I.

[0025] Figure 6 It is a graph in which the reciprocal trigger time 1 / t is plotted as a function of the absorbed optical power A.

[0026] Figure 7is a schematic cross section of a photodetector according to a second embodiment of the present invention.

[0027] Figure 8 is a schematic cross section of a photodetector according to a third embodiment of the present invention.

[0028] Fig. 9 is a schematic cross section of a photodetector according to a fourth embodiment of the present invention.

[0029] Fig.10 is a schematic cross section of a photodetector according to a fifth embodiment of the present invention.

[0030] Fig.11 is a schematic cross section of a photodetector according to a sixth embodiment of the present invention.

[0031] Fig.12 is a schematic cross section of a photodetector according to a seventh embodiment of the present invention.

[0032] Fig.13 is a schematic cross section of a photodetector according to an eighth embodiment of the present invention.

[0033] Fig.14 is a schematic cross section of a photodetector according to a ninth embodiment of the present invention.

[0034] Fig.15 is a schematic cross section of a photodetector according to a tenth embodiment of the present invention.

[0035] Fig.16 The diagram shows a detector array comprising a two-dimensional (2D) array of light sensors, each light sensor of the array being a light detector as described above.

[0036] Fig.17 A photodetector according to any of the above-described embodiments is shown operating as a high-speed photoelectric converter. DETAILED DESCRIPTION

[0037] In the following detailed description, for purposes of explanation rather than limitation, specific details are set forth in order to provide a better understanding of the present disclosure. It will be apparent to those skilled in the art that the present disclosure can be practiced in other embodiments that depart from these specific details.

[0038] Figure 2A and Figure 2B Schematic representation in cross-section and in plan view, respectively, of a photodetector according to a first embodiment of the invention.

[0039] The growth direction, ie the direction orthogonal to the plane of the wafer, is marked as z-direction.The first and second contact regions of the n+ and p+ doped semiconductor regions, respectively, extend in the y-direction. Figure 2A The section AA is Figure 2B The body region 15 is formed in two parts, namely a p-doped semiconductor sub-region 15p adjacent to the n+ contact region and an n-doped semiconductor region 15n adjacent to the p+ contact region, wherein the n-type sub-region and the p-type sub-region have a common interface where they meet. In the x-direction, the structure thus has the order n+pn p+ in the x-direction. The body sub-regions 15p and 15n can be made of a suitable semiconductor material such as silicon or germanium or silicon carbide or a suitable alloy thereof, wherein the band gap is selected to be suitable for absorbing incoming photons hv of the wavelength range to be detected. Highly doped n+ and p+ regions are arranged on either side of the body region 15 beyond the gate and serve as outputs for reading out the photocurrent. The layers of the photodetector are epitaxially fabricated on a semiconductor-on-insulator (SOI) substrate 3 formed by a silicon wafer 7 and an insulator layer 8.

[0040] The photodetector can be operated with the following bias voltages. A negative or zero voltage V1 (e.g., 0 or -1V) is applied to the n+ region and a positive voltage V2 (e.g., +1V) is applied to the p+ region. The n-type and p-type sub-regions of the body region are not biased. The triggering time of the photodetector is a function of the electric field of the body region and can therefore be tuned by adjusting the bias voltages V1 and V2. Under these bias conditions, photons hv incident on the light absorption region, for example from the optical fiber device 30, are absorbed, thereby generating electron-hole pairs, which are then swept out by the electric field induced by the bias voltage, so they are detected as current flowing between the n+ region and the p+ region.

[0041] Figure 3A , Figure 3B and Figure 3C is the energy band diagram along the x direction. Figure 3A The photodetector is shown in reverse bias. Figure 3B and Figure 3C Both show a photodetector in forward bias with a bias voltage V2-V1. Figure 3B shows the conditions that cause the structure to be in a non-conducting state when no light is incident, and Figure 3CThe condition that causes the structure to be in the on-state when light is incident is shown. In the forward bias, when the sensor does not detect any light, almost no current flows between the p+ region and the n+ region due to the potential barrier provided or caused by the bias voltage V2-V1. However, when the sensor detects light, the incident photons are absorbed to generate electron-hole pairs and the sensor changes to the on-state. That is, under the electric field generated by the bias voltage, the holes move toward the n+ contact region and the electrons move toward the p+ contact region. The migrated holes accumulate in the portion of the p-region adjacent to the n+ contact region and induce a reduction in the potential barrier to prevent electron movement and electron current flow from the n+ region. Similarly, the migrated electrons accumulate in the portion of the n-region adjacent to the p+ contact region and induce a reduction in the hole potential barrier and a hole current flowing from the p+ region. In its on-state, the sensor provides a large internal current gain. In addition, the positive feedback mechanism accelerates the accumulation of excess positive negative charge carriers adjacent to the n+ contact region and the p+ contact region, which in turn reduces the associated potential barriers corresponding to such regions and causes current to flow between the p+ region and the n+ region of the photosensor and output current when incident light is detected or in response to incident light.

[0042] Figure 4 is a graph showing the time when incident light is detected (“on”) and not detected (“off”) (i.e. Figure 3C and Figure 3B Schematic graph of the output current of the photodetector as a function of the bias voltage V2-V1 between the n+ contact region and the p+ contact region in the on-state and the non-conducting state (Fig. 1). It should be noted that above the threshold bias voltage Vth, the output current in the on-state is more or less static as the bias voltage varies, which is the preferred mode of operation considering that the incident light intensity is measured by the trigger time rather than the photocurrent amplitude.

[0043] Figure 5A and Figure 5B Oscilloscope screenshots showing the applied voltage Vd=V2-V1 and the output current I in the absence and presence of light, respectively. The trigger time t decreases with increasing light intensity. Figure 5A A triggering time of t0 = 5.5 μs is shown in the absence of light. Figure 5B A trigger time of t1 = 1.5 μs in the presence of light is shown at an absorbed power of 35 nW. The switch from the low current state to the high current state occurs very suddenly, which facilitates accurate measurement of the delay time. The output current of 0.8 mA is more than four orders of magnitude higher than can be achieved with a conventional photodiode at an absorbed power of 35 nW.

[0044] Figure 6is a graph plotting the reciprocal trigger time 1 / t as a function of the absorbed optical power A (in nanowatts). As can be seen, there is a linear relationship between the reciprocal of the trigger time and the absorbed optical power.

[0045] Figure 7 is a schematic cross-section of a vertical photodetector according to a second embodiment of the invention. By vertical, we mean that the layers are epitaxially formed in the xy plane, which is the plane of the substrate, so the layer sequence is in the z direction. The structure is subdivided into individual pixels in a one-dimensional row array or a two-dimensional row and column array by insulating trenches filled with dielectric material, which electrically isolates adjacent pixels from each other. For example, the dielectric material can be a material deposited after etching, or a material produced by an oxidation process after etching. Instead of filling the trenches with dielectric material, they may be left unfilled or only partially filled by a thin layer of oxide or other insulating material coating the sides of the trenches. The insulating trenches thus extend vertically through the light absorption region and at least one of the contact regions so as to subdivide the photodetector into an array of independently contacted pixels.

[0046] The semiconductor layers are deposited on a suitable substrate in the order of p+np n+ as shown or in the reverse order. Depending on the need, the doping of each layer can be achieved at the time of deposition or by a post-deposition process such as ion implantation, or a combination of the two. The n-type layer and the p-type layer form the light absorption region of the detector, and the n+ layer and the p+ layer form its contact region. The n-type layer and the p-type layer have an interface forming a pn junction. The n-type layer and the p-type layer have a band gap suitable for absorbing incident light photons hv in a specified wavelength (energy) range and generate electron and hole pairs, which drift toward the p+ layer and the n+ layer, respectively, when the pn junction is under forward bias. When the device is under forward bias, the electron-hole pairs generated by absorbing photons in the p layer (as schematically illustrated) or in the n layer are separated by the electric field induced by the forward bias, wherein the holes drift toward the n+ layer and the electrons drift toward the p+ layer. The substrate is not shown, but a suitable substrate may be provided, such as a p+ substrate for a pixel that ohmically contacts the p+ layer. When the structure is switched from reverse bias to forward bias with respect to the pn junction, electron-hole pairs generated by photon absorption initiate current flow between the contacts once a sufficient number of electrons and holes have drifted to sufficiently reduce the potential barrier. There is therefore a time delay from the reverse to forward bias switching event to the start of current flow that is inversely proportional to the incident light intensity.

[0047] The photodetector operates by switching from reverse bias to forward bias in repeated cycles. That is, the operation proceeds by the following steps: applying a voltage to reverse bias the n+ contact and the p+ contact; switching the reverse bias voltage to a forward bias voltage. After switching, the electrons and holes generated in the light absorption region in response to photon absorption drift toward the p+ contact region and the n+ contact region, respectively. The device then senses the start of current flow between the first contact and the second contact. The time delay between the switching and the start is measured, which is inversely proportional to the incident light intensity. This reverse to forward bias sequence is then repeated. The repeated cycles of driving and reading out can be periodic or non-periodic. In the periodic case, the duration of the forward bias and reverse bias segments is fixed. In the non-periodic case, the reverse bias segment has a fixed duration, but the forward bias duration varies in response to the incident light intensity within a time window set between a minimum and a maximum value. After the start of the current has occurred and the time delay has been measured, the forward bias segment of the cycle can be terminated. The forward bias duration will then have a maximum value when there is no incident light because there will be no onset of current flow, and a minimum value when the incident light intensity is high because the time delay will be shorter than the minimum value, but will have intermediate values ​​when the incident light intensity is such that the time delay for the onset of current flow is within the window.

[0048] Figure 8 is a schematic cross-section of a vertical light detector according to a third embodiment of the present invention, which will be mainly based on Figure 7 , can be understood from the previous discussion of . In a third embodiment, each pixel is composed of a group of sub-pixels. As in the second embodiment, each pixel is defined by a dielectric material groove extending through the entire structure (i.e., through the n+pn p+ layer). The sub-pixels of a given pixel are separated from each other by a dielectric material groove, but partially, but not entirely, extending through the structure (i.e., at least through the top contact layer (here n+) and at least partially through the upper part of the light absorbing layer (here p) and possibly also partially through the lower part of the light absorbing layer (here n)). Each pixel is therefore subdivided into a one-dimensional or two-dimensional array of sub-pixels by additional insulating grooves, and for each pixel, the additional insulating grooves are laterally located inside the insulating grooves defining the pixel and extend vertically through one of the contact areas and at least one of the light absorbing areas, but not as far as another contact area in the contact area, so that the sub-pixels of any one pixel remain in normal contact. The sub-pixel structure can be used to reduce internal capacitance and thus provide better sensitivity.

[0049] Fig. 9 is a schematic cross section of a vertical photodetector according to a fourth embodiment of the present invention. Figure 7The photodetector structure shown is combined with a semiconductor circuit layer arranged on the upper contact area. The circuit layer includes an array of readout sensors for the pixel array of the photodetector, wherein the sensor-to-pixel connection is realized using vias. In particular, the circuit layer can be a CMOS circuit layer that is electrically connected to the pixel using through silicon vias (TSVs). A bias voltage can then be applied to the n+ contact area and the p+ contact area through the TSVs. In addition, a signal current induced by the incident light hv can be detected on a per-pixel basis through the TSV connection. The CMOS circuit layer is shown as being arranged on the n+ contact layer, but alternatively it can be arranged on the p+ contact layer. Figure 7 The structure can also be combined with a CMOS circuit layer in a similar manner.

[0050] Fig.10 is a schematic cross-section of a light detector according to a fifth embodiment of the present invention. This embodiment can be understood as Figure 7 A variation of the embodiment, in that the epitaxial layer structure includes a p+ contact layer, an n-type layer and a p-type layer from bottom to top, wherein the n-type layer and the p-type layer form a light absorption region. However, instead of forming the top contact as an epitaxial layer, the top contact is formed in the p-type epitaxial layer with one or more embedded regions. Two adjacent embedded regions are shown, wherein the arrangement of adjacent embedded regions can be used to define pixels. Alternatively, a dielectric material groove can be used as described in other embodiments. It should also be noted that in some embodiments as schematically illustrated, light hv can be incident from the split side surface. The substrate is not shown, but a suitable substrate can be provided, such as a p+ substrate for ohmic contact to the p+ layer. It should also be understood that the opposite structure can be achieved, i.e. as shown but wherein n+--->p+, p-->n, n-->p and p+-->n+.

[0051] Fig.11 is a schematic cross-section of a light detector according to a sixth embodiment of the present invention. Figure 2A A horizontal n+pn p+ structure somewhat similar to the / 2B structure is used. A p-type layer is epitaxially deposited on a substrate 3. In the p-type layer, an embedded n-type region is formed, and a p+ contact region is formed within the n-type region. Laterally offset from the n-type region, an n+ contact region is formed in the p-type layer. It will also be understood that the opposite structure can be achieved. In addition, the substrate 3 is not an electrically active part of the device, so it can be, for example, an n-type, p-type, semi-insulating (SI) semiconductor, sapphire or insulator, as required.

[0052] Fig.12 is a schematic cross section of a photodetector according to a seventh embodiment of the present invention. A p-type or n-type substrate 3 is provided. In the surface of the substrate, an embedded n-type region is formed, and a p+ contact region is formed within the n-type region. Laterally offset from the n-type region, a p-type embedded region is formed, and an n+ contact region is formed within that.

[0053] Fig.13 is a schematic cross-section of a light detector according to an eighth embodiment of the present invention. Fig.12 A variant of the embodiment wherein Fig.12 The role of the substrate in the device is assumed by the epitaxial layer. The substrate 3 is therefore not an electrically active part of the device and can therefore be, for example, an n-type, p-type, semi-insulating (SI) semiconductor, sapphire or an insulator, as required.

[0054] Fig.14 is a schematic cross-section of a photodetector according to a ninth embodiment of the present invention. A p-type layer is deposited on a substrate. In the p-type layer, an embedded n-type region is formed, and a p-type region is formed within the n-type region, and a p+ contact region is formed within the p-type region. An n+ contact region is formed in the p-type layer laterally offset from the n-type region. It should also be understood that the opposite structure can be achieved. In addition, the substrate 3 is not an electrically active part of the device, so it can be, for example, an n-type, p-type, semi-insulating (SI) semiconductor, sapphire or insulator, as required. In this device structure, the active pn junction is the one pointed to in the figure in terms of time-delayed light-induced current.

[0055] Fig.15 is a schematic cross section of a photodetector according to the tenth embodiment of the present invention. A p-type layer is deposited on a p+ substrate 3. In the p-type layer, an embedded n-type region is formed, and a p-type region is formed within the n-type region, and an n+ contact region is formed within the p-type region. Laterally offset from the n-type region, a p+ contact region is formed in the p-type layer. It should also be understood that the opposite structure can be achieved. In this device structure, the active pn junction is the one pointed to in the figure in terms of time-delayed light-induced current.

[0056] Fig.16 The detector array is shown as including a two-dimensional (2D) array of light sensors 5, each light sensor of the array being a light detector as described above. In addition to the array of sensors, the detector array may also include a control circuit system 25 to manage the acquisition, capture and / or sensing operations of the light sensors of the array by outputting appropriate control signals. For example, the control circuit system (which may be integrated on the same substrate as the sensor) may control or enable / disable the sensor in a manner such that data acquisition or sensing is related to the data rate of the transmission; the detector array may be coupled to a plurality of fiber optic output devices, wherein each fiber optic device is associated with one or a group of sensors in the sensor. The sensors may be configured and / or arranged in any array architecture and in combination with any type of integrated circuit system. In addition, any manufacturing technology may be used to make the array.

[0057] Fig.17A photodetector according to any of the above embodiments is shown coupled to an optional current amplifier. The photodetector is illustrated in operation as a high-speed photoelectric converter operable to convert an optical pulse train of incident light hv or other more complex signal into an equivalent electrical pulse train or other more complex signal. The pulse train schematically illustrated above shows the optical signal transmitted by the optical fiber 30, and the pulse train schematically illustrated below shows the electrical signal output by the photodetector having received the optical signal as input. Due to the large output signal, the photodetector does not require an amplifier and can be directly connected to a digital circuit. Not requiring an amplifier is advantageous because amplifiers are noise sources.

[0058] It should be noted that the term "circuit" may particularly mean a single component or multiple components (whether in the form of an integrated circuit or otherwise) that are active and / or passive and are coupled together to provide or perform a desired function. The term "circuitry" may particularly mean a circuit (whether integrated or otherwise), a group of such circuits, one or more processors, one or more state machines, one or more processors implementing software, one or more gate arrays, programmable gate arrays and / or field programmable gate arrays, or a combination of one or more circuits (whether integrated or otherwise), one or more state machines, one or more processors, one or more processors implementing software, one or more gate arrays, programmable gate arrays and / or field programmable gate arrays. The term "data" may particularly mean a current or voltage signal, whether in analog or digital form, which may be a single bit (or the like) or multiple bits (or the like).

[0059] It should be further noted that the various circuits and circuit systems disclosed herein can be described using computer-aided design tools and expressed (or represented) as data and / or instructions embodied in various computer-readable media, for example, in terms of their behavior, register transfers, logic components, transistors, layout geometry, and / or other characteristics. The formats of files and other objects in which such circuit expressions can be implemented include, but are not limited to, formats that support behavioral languages ​​such as C, Verilog, and HLDL, formats that support register-level description languages ​​like RTL, and formats that support geometric description languages ​​such as GDSII, GDSIII, GDSIV, CIF, MEBES, and any other suitable formats and languages. Computer-readable media in which such formatted data and / or instructions can be embodied include, but are not limited to, various forms of non-volatile storage media (e.g., optical, magnetic, or semiconductor storage media) and carriers that can be used to transfer such formatted data and / or instructions via wireless, optical, or wired signal media, or any combination thereof. Examples of transfers of such formatted data and / or instructions by carriers include, but are not limited to, transfers (uploads, downloads, emails, etc.) over the Internet and / or other computer networks via one or more data transfer protocols (e.g., HTTP, FTP, SMTP, etc.). The present invention is also directed to such representations of circuitry described herein and / or techniques implemented thereby, and therefore, are intended to fall within the scope of the present invention.

[0060] In practice, when received within a computer system via one or more computer-readable media, the above-described circuitry based on such data and / or instruction representations can be processed by a processing entity (e.g., one or more processors) within the computer system in conjunction with the execution of one or more other computer programs, including but not limited to a netlist generator, a placement and routing program, etc., to generate a representation or image of the physical manifestation of such circuitry. Such a representation or image can thereafter be used in device fabrication, for example, by enabling the generation of one or more masks for forming various components of the circuitry during device fabrication.

[0061] In addition, various circuits and circuit systems and technologies disclosed herein can be represented via simulations using computer-aided design, simulation and / or testing tools and expressions based on simulation instructions. The simulation of the circuit system of the present invention including the photodetector and / or the technology implemented thereby can be implemented by a computer system, wherein the characteristics and operations of such circuit system and the technology implemented thereby are simulated, imitated, copied, analyzed and / or predicted via the computer system. The present invention is also directed to such simulations and tests of the inventive device and / or circuit system and / or the technology implemented thereby, and therefore, is intended to fall within the scope of the present invention. Computer-readable media and data corresponding to such simulation and / or testing tools are also intended to fall within the scope of the present invention.

[0062] It will be apparent to those skilled in the art that many improvements and modifications can be made to the foregoing exemplary embodiments without departing from the scope of the present disclosure.

Claims

1. A photodetector device, comprising: a first light absorption region and a second light absorption region, the first light absorption region and the second light absorption region being composed of a semiconductor material and being doped n-type and p-type, respectively, wherein the first light absorption region and the second light absorption region are formed as respective epitaxial layers arranged on top of each other over a substrate, wherein the light absorption regions are configured to generate electron and hole pairs in response to absorption of photons when light is incident on the device; a first contact region and a second contact region, the first contact region and the second contact region being made of a semiconductor material and being doped p-type and n-type, respectively, wherein the contact regions have a higher doping concentration than the light absorbing region and are labeled p+ and n+, respectively; and a first contact and a second contact, the first contact and the second contact being connected to the first contact region and the second contact region, respectively, wherein the first light absorption region and the second light absorption region and the second contact region and the first contact region are arranged above the substrate in an n+pn p+ continuous order, so that after the voltage applied between the second contact and the first contact is switched to change the junction of the n+pn p+ continuous order from reverse bias to forward bias, the electrons and holes generated in the light absorption region in response to photon absorption drift toward the first contact region and the second contact region, respectively, which causes the current to begin to flow between the contacts after a time delay inversely proportional to the intensity of the incident light.

2. The device of claim 1, further comprising an isolation trench extending vertically through the light absorbing region and at least one of the contact regions to subdivide the photodetector into an array of independently contacted pixels.

3. The device of claim 2 , further comprising a semiconductor circuit layer disposed on the epitaxial layer forming one of the first contact region and the second contact region, the circuit layer comprising an array of readout sensors for the pixel array of the photodetectors electrically connected to the pixels using vias.

4. The device according to claim 2, wherein Each pixel is subdivided into an array of sub-pixels by further insulating trenches, and for each pixel, the further insulating trenches are laterally arranged inside the insulating trenches defining the pixel and extend vertically through one of the contact areas and at least one of the light absorption areas, but not as far as another of the contact areas, so that the sub-pixels of any pixel remain in contact.

5. The device according to claim 1, wherein The first light absorption region and the second light absorption region are arranged so that one of the first light absorption region and the second light absorption region is formed as an epitaxial layer on the substrate, or is formed integrally with the substrate, and the other of the first light absorption region and the second light absorption region is formed as an embedded region within the epitaxial layer.

6. The device according to claim 1, wherein The first light absorption region and the second light absorption region are arranged so that one of the first light absorption region and the second light absorption region is formed in the first part as an epitaxial layer on the substrate or integrally with the substrate, and is formed in the second part as an embedded region within the epitaxial layer or the substrate, and wherein the other of the first light absorption region and the second light absorption region is formed as another embedded region within the epitaxial layer.

7. The device according to claim 6, wherein The embedded region and the further embedded region are laterally separated by a portion of the epitaxial layer or the substrate.

8. The device according to claim 6, wherein One of the first contact region and the second contact region is formed as yet another embedded region within the embedded region of the first light absorption region or the second light absorption region, respectively.

9. The device according to claim 6, wherein The first contact region and the second contact region are formed as respective further embedded regions within the embedded regions of the first light absorption region and the second light absorption region, respectively.

10. The device according to claim 1, wherein One of the first contact region and the second contact region is formed as an epitaxial layer on the substrate, and at least one of the first light absorption region and the second light absorption region is at least partially formed as an additional epitaxial layer on the epitaxial layer of the one of the first contact region and the second contact region.

11. The device according to claim 1, wherein At least one of the first contact region and the second contact region is respectively formed as an embedded region within an epitaxial layer that forms at least a portion of the first light absorption region and the second light absorption region.

12. The device according to claim 1, wherein The first and second contact regions are formed as respective laterally spaced first and second embedded regions within an epitaxial layer that forms at least a portion of the first and second light absorbing regions.

13. The device according to claim 1, wherein One of the first and second contact regions is formed as laterally spaced first and second embedded regions, respectively, formed within an epitaxial layer that forms at least a portion of one of the first and second light absorbing regions.

14. A method for manufacturing a photodetector device, the method comprising: fabricating a first light absorption region and a second light absorption region using semiconductor materials doped n-type and p-type, respectively, wherein the first light absorption region and the second light absorption region are fabricated as respective epitaxial layers arranged on top of each other over a substrate, wherein the light absorption regions are configured to generate electron and hole pairs in response to absorption of photons when light is incident on the device; Making a first contact region and a second contact region made of semiconductor material and doped to p-type and n-type, respectively, wherein the contact regions have a higher doping concentration than the light absorbing region and are marked as p+ and n+, respectively; and providing a first contact and a second contact connected to the first contact area and the second contact area, respectively, wherein the first light absorption region and the second light absorption region and the second contact region and the first contact region are arranged above the substrate in an n+pn p+ continuous order, so that after the voltage applied between the second contact and the first contact is switched to change the junction of the n+pn p+ continuous order from reverse bias to forward bias, the electrons and holes generated in the light absorption region in response to photon absorption drift toward the first contact region and the second contact region, respectively, which causes the current to begin to flow between the contacts after a time delay inversely proportional to the intensity of the incident light.

15. The method of claim 14, further comprising making an insulating trench extending vertically through the light absorbing region and at least one of the contact regions to subdivide the photodetector into an array of independently contacted pixels.

16. A method of operating a photodetector device, the method comprising: A photodetector device is provided, the photodetector device having: a first light absorption region and a second light absorption region, the first light absorption region and the second light absorption region being composed of a semiconductor material and being doped n-type and p-type, respectively, wherein the first light absorption region and the second light absorption region are fabricated as respective epitaxial layers arranged on top of each other over a substrate, wherein the light absorption regions are configured to generate electron and hole pairs in response to absorption of photons when light is incident on the device; a first contact region and a second contact region, the first contact region and the second contact region being made of a semiconductor material and being doped p-type and n-type, respectively, wherein the contact regions have a higher doping concentration than the light absorbing region and are labeled p+ and n+, respectively; and a first contact and a second contact, the first contact and the second contact being connected to the first contact region and the second contact region, respectively, wherein the first light absorption region and the second light absorption region and the second contact region and the first contact region are arranged above the substrate in an n+pn p+ sequential order; and The photodetector device is operated by repeating: applying a voltage to reverse bias the second contact and the first contact; switching the reverse bias voltage to a forward bias voltage to change the n+pn p+ sequential junction from reverse bias to forward bias, so that after the switching, electrons and holes generated in the light absorption region in response to photon absorption drift toward the first contact region and the second contact region, respectively; and The initiation of current flow between the first contact and the second contact is sensed and a time delay between the switching and the initiation is measured, wherein the time delay is inversely proportional to the intensity of the incident light.

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