High-speed high-response multimode photoelectric detector chip based on electric field regulation and control

Abstract

The invention relates to a high-speed high-response multimode photoelectric detector chip based on electric field regulation and control, and belongs to the technical field of near-infrared photoelectric detection. The photoelectric detector chip comprises tube cores arranged in an array mode, each tube core comprises a semiconductor epitaxial structure, an anti-reflection film, metal electrodes located on the surfaces of the semiconductor epitaxial structure and the anti-reflection film and a metal bonding pad formed on the surface of the chip, and the metal electrodes extend to the metal bonding pad through the surface of the anti-reflection film. The semiconductor epitaxial structure comprises a P-type contact layer, an N-type contact layer and a depletion layer between the two contact layers, and the depletion layer comprises an absorption layer, a cliff layer and a collection layer. By optimizing the design of the semiconductor epitaxial structure, the electric field distribution in the depletion layer is accurately regulated and controlled, so that photon-generated carriers are transported at an over-saturation speed, and the response speed of a detector chip is greatly improved. And meanwhile, the photon absorption rate is considered, so that the detector chip obtains high responsivity, and the problem of mutual restriction of bandwidth and responsivity is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of near-infrared photoelectric detection, and relates to a high-speed and high-response multi-mode photoelectric detector chip based on electric field regulation. Background Art

[0002] With the rapid development of cloud computing, big data, and artificial intelligence, the demand for data transmission between data centers has exploded. Multimode fiber optic communications are widely used in short-distance data center optical interconnects due to their cost-effectiveness and ease of connection. Multimode photodetector chips based on III-V compound semiconductors are key components that enable high-speed data transmission and meet the urgent bandwidth needs of data centers. Multimode photodetector chips based on III-V compound semiconductors are mainly divided into PIN type and avalanche photodiode (APD) type. PIN type detectors are suitable for high-speed applications due to their fast response speed and low cost.

[0003] Multimode optical fiber and its supporting components are relatively low-cost, offering an economic advantage in short-distance, high-speed transmission scenarios that are insensitive to modal dispersion. However, to accommodate the different modes of light propagation, multimode optical fiber typically has a larger core diameter, typically 50μm or 62.5μm. This large core diameter poses challenges for fiber coupling to the detector chip. To ensure responsiveness, surface-incident detector chips require high coupling efficiency with the multimode fiber, necessitating a larger photosensitivity surface. A larger photosensitivity surface increases the capacitance of the detector chip, reducing its bandwidth. Reducing capacitance by increasing the thickness of the depletion layer in a PIN detector increases the transit time of photogenerated carriers, similarly reducing the device's bandwidth and making it difficult to meet the high-speed data transmission requirements of data centers.

[0004] Several approaches have been developed to address the trade-off between device responsivity and bandwidth, such as the use of lensed fiber arrays or back-incident flip-chip mounting. However, these approaches increase overall system cost and fail to address the conflict between the chip's photosensitivity and its optoelectronic bandwidth at the chip structure level. Therefore, increasing the bandwidth of multimode photodetector chips while maintaining photoresponsivity has become a hot topic in recent years in improving the overall performance of photodetector chips. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a high-speed and high-response multi-mode photodetector chip based on electric field regulation, so as to solve the contradiction between the size of the chip's photosensitive surface and the chip's photoelectric bandwidth from the chip structure level, thereby improving the bandwidth of the multi-mode photodetector chip while ensuring the light response.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A high-speed, high-response multi-mode photodetector chip based on electric field regulation includes multiple tube cores arranged in an array, each tube core has the same structure, and its structure includes a substrate, a semiconductor epitaxial structure located on the surface of the substrate, an anti-reflection film covering the semiconductor epitaxial structure, metal electrodes formed on the surfaces of the semiconductor epitaxial structure and the anti-reflection film, and a metal pad formed on the surface of the chip.

[0008] The semiconductor epitaxial structure comprises, from bottom to top, an N-type contact layer, a depletion layer, and a P-type contact layer, wherein the depletion layer is located between the P-type contact layer and the N-type contact layer. The depletion layer comprises, from bottom to top, a collection layer, a cliff layer, and an absorption layer.

[0009] Furthermore, the thickness of the P-type contact layer is 50 nm to 500 nm, and the p-type doping concentration is 2×10 18 cm -3 ~1×10 19 cm -3 The n-type contact layer has an n-doping concentration of 1×10 18 cm -3 ~5×10 18 cm -3 .

[0010] Furthermore, the collection layer has a thickness of 500 nm to 1500 nm and an n-doping concentration of 5×10 14 cm -3 ~1×10 16 cm -3 .

[0011] Furthermore, the cliff layer has a thickness of 20 nm to 50 nm and a doping concentration of 5×10 14 cm -3 ~1×10 18 cm -3 .

[0012] Furthermore, the absorption layer has a thickness of 500 nm to 1500 nm and an n-doping concentration of 5×10 14 cm -3 ~1×10 18 cm -3 .

[0013] Furthermore, the metal electrode includes a P electrode and an N electrode, the P electrode contacts the surface of the P-type contact layer, and the N electrode contacts the surface of the N-type contact layer.

[0014] The P electrode contacts the surface of the P-type contact layer through an etched electrode window, is led out from the surface of the P-type contact layer, extends through the surface of the anti-reflection film to the P pad, and is connected to the P pad. The N electrode also contacts the surface of the N-type contact layer through an etched electrode window, is led out from the surface of the N-type contact layer, extends through the surface of the anti-reflection film to the N pad, and is connected to the N pad.

[0015] Furthermore, the reflectivity of the anti-reflection film is less than 5%.

[0016] The beneficial effects of the present invention are as follows: the present invention proposes a high-speed, high-response multi-mode photodetector chip based on electric field regulation. The present invention optimizes the thickness and doping concentration of each layer in the semiconductor epitaxial structure to accurately control the electric field distribution in the depletion layer, so that the carriers in the depletion layer can be transported at a speed exceeding the saturation rate, thereby improving the response speed of the device; by precisely optimizing the shape and size of the metal electrode, the high-frequency output characteristics of the detector chip are enhanced and the device bandwidth is improved; by optimizing the depletion layer thickness, a smaller capacitance can be maintained when the photosensitive surface is larger, so the detector chip can have a larger photosensitive surface, ensuring good fiber coupling quality; by optimizing the design of the anti-reflection film, the reflectivity of the incident light is reduced, thereby improving the responsiveness of the detector chip.

[0017] Compared with traditional high-speed photodetector chips, the present invention designs a precisely modulated semiconductor epitaxial structure so that the chip has an optimized electric field distribution under a certain bias voltage and has a higher responsiveness. It breaks through the problem of mutual constraints between bandwidth, responsiveness and capacitance in traditional photodetectors, and increases the chip bandwidth without affecting the responsiveness of the detector chip, greatly improving the overall performance of the high-speed photodetector chip, laying the foundation for the widespread application of short-distance high-speed data transmission in scenarios such as data centers, cloud computing and high-speed digital communications.

[0018] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0020] Figure 1 This is a simulation diagram of a high-speed, high-response, multi-mode photodetector chip based on electric field regulation according to an embodiment of the present invention;

[0021] Figure 2 A schematic half-section diagram of a die structure in a photodetector chip provided in one embodiment of the present invention;

[0022] Figure 3 is the relationship between electron drift velocity and electric field strength in InGaAs and InP materials;

[0023] Figure 4 The electric field intensity distribution and electron drift velocity distribution in the depletion layer of the detector chip simulated and designed for one embodiment of the present invention;

[0024] Figure 5 Comparison of frequency response characteristics test results and simulation results of a high-speed, high-response, multi-mode photodetector chip based on electric field regulation manufactured according to an embodiment of the present invention.

[0025] Figure numerals: 110 - semi-insulating substrate; 120 - N-type contact layer; 130 - collection layer; 131 - cliff layer; 132 - absorption layer; 140 - P-type contact layer; 210 - anti-reflection film; 310 - P electrode; 311 - N electrode; 410 - P pad; 411: N pad. DETAILED DESCRIPTION

[0026] The following describes the embodiments of the present invention by means of specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0027] Among them, the accompanying drawings are only for illustrative purposes and represent only schematic diagrams rather than actual pictures, and should not be understood as limiting the present invention. In order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the dimensions of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the accompanying drawings.

[0028] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "back", etc. indicating directions or positional relationships, they are based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0029] The high-speed, high-response, multi-mode photodetector chip based on electric field regulation proposed in this invention comprises multiple die arranged in an array. Each die includes a semiconductor epitaxial structure, an antireflection film, and a metal electrode located on the antireflection film. The semiconductor epitaxial structure comprises a P-type contact layer, an N-type contact layer, and a depletion layer. The depletion layer is located between the P-type and N-type contact layers and comprises an absorption layer, a cliff layer, and a collection layer.

[0030] In the optical communications industry, the detector chips used in optical modules are typically based on III-V semiconductors, namely, semiconductor materials such as GaAs and InGaAs. In the application scenario of short-distance optical interconnection in data centers, the mainstream near-infrared light wavelength used is 850nm. The InGaAs / InP material system has a higher absorption coefficient at 850nm than the GaAs / AlGaAs material system and a higher electron mobility, which is more advantageous when manufacturing high-speed multimode photodetector chips. Therefore, the high-speed, high-response multimode photodetector chip proposed in the embodiment of the present invention uses InGaAs / InP-based semiconductors as materials.

[0031] Example 1

[0032] Figure 1 The figure shows a simulation diagram of a high-speed, high-response, multi-mode photodetector chip based on electric field regulation provided by this embodiment. The metal electrodes of the chip are designed through simulation, and the shape and size are as follows: Figure 1 shown.

[0033] In this embodiment, the structure of each die in the photodetector chip is as follows: Figure 2 As shown, it includes a non-insulating substrate 110 , a semiconductor epitaxial structure, an anti-reflection film 210 , metal electrodes 310 , 311 and metal pads 410 , 411 .

[0034] The semiconductor epitaxial structure is composed of a P-type contact layer 140, an N-type contact layer 120, and a depletion layer, wherein the depletion layer is located between the P-type contact layer 140 and the N-type contact layer 120. The depletion layer includes, from bottom to top, a collection layer 130, a cliff layer 131, and an absorption layer 132.

[0035] In this embodiment, the non-insulating substrate 110 , the N-type contact layer 120 , the collection layer 130 , and the cliff layer 131 are made of InP material, and the absorption layer 132 and the P-type contact layer 140 are made of InGaAs material.

[0036] The thickness of the N-type contact layer 120 can be adjusted as needed. The n-doping concentration in the N-type contact layer is 1×10 18 cm -3 ~5×10 18 cm -3 In this embodiment, the preferred thickness of the N-type contact layer 120 is 500 nm, and the preferred n-doping concentration is 5×10 18 cm -3 .

[0037] The thickness of the collection layer 130 is 500 nm to 1500 nm, and the n-doping concentration is 5×10 14 cm -3 ~1×10 16 cm -3 In this embodiment, the preferred thickness of the collection layer 130 is 1300 nm, and the preferred n-doping concentration is 5×10 14 cm -3 .

[0038] The thickness of the cliff layer 131 is 20nm to 50nm, and can be p-doped or n-doped, with a doping concentration of 5×10 14 cm -3 ~1×10 18 cm -3 In this embodiment, the preferred thickness of the cliff layer 131 is 30 nm, and the preferred p-doping concentration is 2×10 16 cm -3 .

[0039] The thickness of the absorption layer 132 is 500 nm to 1500 nm, and the n-doping concentration is 5×10 14 cm -3 ~1×10 18 cm -3 In this embodiment, the preferred thickness of the absorption layer 132 is 1150 nm, and the preferred n-doping concentration is 5×10 14 cm -3 .

[0040] The thickness of the P-type contact layer 140 is 50 nm to 500 nm, and the p-type doping concentration is 2×10 18 cm -3 ~1×10 19 cm -3 In this embodiment, the preferred thickness of the P-type contact layer 140 is 200 nm, and the preferred p-doping concentration is 1×10 19 cm -3 .

[0041] like Figure 2 As shown, in this embodiment, the anti-reflection film 210 is formed by depositing a layer of SiN with a specific thickness on the surface of the semiconductor epitaxial structure. x Thin film formation. SiN x The thickness of the film is 0-400 nm, preferably 100 nm in this embodiment. When the thickness of the anti-reflection film 210 is 100 nm, the surface reflectivity is less than 3%.

[0042] like Figure 2 As shown, in this embodiment, the metal electrodes include a P-electrode 310 and an N-electrode 311. The P-electrode 310 and the N-electrode 311 are formed by depositing a layer of metal on the surface of the semiconductor epitaxial structure and the anti-reflection film 210. It should be noted that in the photodetector chip, the functional layers included in each die are cylindrical, and the radius of the N-type contact layer 120 is larger than the radius of its surface collection layer 130, cliff layer 131, absorption layer 132, and P-type contact layer 140.

[0043] On the surface of the N-type contact layer 120, except for the collection layer 130, an electrode window is formed by etching the anti-reflection film. The electrode window surrounds the collection layer 130 but is not closed, that is, the electrode window has two ends. Metal is deposited in the electrode window and extended from the electrode window through the anti-reflection film surface to the outside of the semiconductor epitaxial structure. The metal is then shaped to form a Figure 1 The N electrode 311 and the N pad 411 are shown.

[0044] Similarly, on the surface of the P-type contact layer 140, an electrode window is formed by etching the anti-reflection film. The electrode window is a smaller fan-shaped ring window. Metal is deposited in the electrode window and extended from the electrode window through the anti-reflection film surface to the outside of the semiconductor epitaxial structure. The metal is then shaped to form a structure as shown in FIG. Figure 1 The P electrode 310 and the P pad 410 are shown.

[0045] The metal type and thickness of the P electrode 310 , N electrode 311 , P pad 410 , and N pad 411 can be adjusted as needed. In this embodiment, the thickness of the P electrode 310 , N electrode 311 , P pad 410 , and N pad 411 is preferably 2000 nm.

[0046] like Figure 3 As shown in the figure, in this embodiment, the depletion layer materials InP and InGaAs used in the semiconductor epitaxial structure exhibit different electron drift velocities under different electric fields. It can be seen that the electron drift velocity first increases and then decreases with increasing electric field strength. The higher the electron drift velocity, the faster the electrons generated by the incident light are transported within the chip, and the faster the chip response speed.

[0047] Figure 4 The figure shows the electric field distribution and electron drift velocity distribution of the semiconductor epitaxial structure under 3V bias. Figure 4 It can be seen that the semiconductor epitaxial structure described in this embodiment can optimize the electric field distribution in the depletion region, so that electrons have a high transport velocity.

[0048] Figure 5 The following are the simulation results and test results of the frequency response characteristics of the high-speed and high-response multi-mode photodetector chip based on electric field control in this embodiment. Figure 5 It can be seen that the simulation results of the frequency response characteristics of the photodetector chip are in good agreement with the test results. The chip has a 3dB cutoff frequency of 30GHz, which enables high-speed data transmission of 100Gb / s per channel under PAM4 modulation.

[0049] As an improvement based on traditional high-speed photodetector chips, the present invention designs a precisely modulated semiconductor epitaxial structure to enable the chip to have an optimized electric field distribution under a certain bias voltage and a high responsiveness. This breaks through the problem of the mutual constraints of bandwidth, responsiveness, and capacitance in traditional photodetectors, increases the chip bandwidth without affecting the responsiveness of the detector chip, greatly improving the overall performance of the high-speed photodetector chip, and laying the foundation for the widespread application of short-distance, high-speed data transmission in scenarios such as data centers, cloud computing, and high-speed digital communications.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A high-speed, high-response multi-mode photodetector chip based on electric field regulation, characterized in that: It comprises a plurality of tube cores arranged in an array, each of which has the same structure, including a substrate, a semiconductor epitaxial structure located on the surface of the substrate, an anti-reflection film covering the semiconductor epitaxial structure, metal electrodes formed on the surface of the semiconductor epitaxial structure and the anti-reflection film, and a metal pad formed on the surface of the chip.

2. The photodetector chip according to claim 1, wherein: The semiconductor epitaxial structure includes an N-type contact layer, a depletion layer and a P-type contact layer, wherein the depletion layer is located between the P-type contact layer and the N-type contact layer; the depletion layer includes a collection layer, a cliff layer and an absorption layer from bottom to top.

3. The photodetector chip according to claim 2, wherein: The thickness of the P-type contact layer is 50nm to 500nm, and the p-doping concentration is 2×10 18 cm -3 ~1×10 19 cm -3 The n-type contact layer has an n-doping concentration of 1×10 18 cm -3 ~5×10 18 cm -3 .

4. The photodetector chip according to claim 2, wherein: The collection layer has a thickness of 500 nm to 1500 nm and an n-doping concentration of 5×10 14 cm -3 ~1×10 16 cm -3 .

5. The photodetector chip according to claim 2, wherein: The cliff layer has a thickness of 20 nm to 50 nm and a doping concentration of 5×10 14 cm -3 ~1×10 18 cm -3 .

6. The photodetector chip according to claim 2, wherein: The absorption layer has a thickness of 500 nm to 1500 nm and an n-doping concentration of 5×10 14 cm -3 ~1×10 18 cm -3 .

7. The photodetector chip according to claim 2, wherein: The metal electrode includes a P electrode and an N electrode, and the metal pad includes a P pad and an N pad; the P electrode contacts the surface of the P-type contact layer, extends to the P pad through the surface of the anti-reflection film, and is connected to the P pad; the N electrode contacts the surface of the N-type contact layer, extends to the N pad through the surface of the anti-reflection film, and is connected to the N pad.

8. The photodetector chip according to claim 1, 2 or 7, characterized in that: The reflectivity of the anti-reflection film is less than 5%.

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