Medium-wave avalanche photodiode and medium-wave infrared detector

Abstract

According to the medium-wave avalanche photodiode and the medium-wave infrared detector provided by the invention, a separation absorption and multiplication structure is adopted, InAs / GaSb class-II superlattice with an adjustable band gap is selected as an absorption layer, AlInAsSb with a high ionization coefficient is selected as a multiplication layer, and the thickness and doping concentration of each layer are accurately optimized; the invention aims at intensively limiting a high electric field to a multiplication layer to promote an avalanche effect and enabling an absorption layer to be in a low electric field to suppress tunneling dark current. According to the structure provided by the invention, the gain up to 85.2 is realized under 62V bias voltage, the light response wave band completely covers 3-5 microns, and the responsivity of 3A / W is reached at 3.08 microns, so that the targets of high internal signal amplification capability and high-efficiency medium-wave infrared photoelectric conversion are synchronously achieved, and the sensitivity of the detector is effectively improved.

Description

Technical Field

[0001] This invention relates to the field of electronic components technology, and in particular to a mid-wave avalanche photodiode and a mid-wave infrared detector. Background Technology

[0002] Mid-wave infrared (MWIR, typically referring to the 3-5 micrometer band) detection technology plays an irreplaceable role in numerous fields such as military reconnaissance, precision guidance, astronomical observation, environmental monitoring, and industrial non-destructive testing. In this band, the thermal radiation characteristics of target objects are significant, and the atmospheric transmission window is excellent, thus the demand for high-performance mid-wave infrared detectors is increasingly urgent. Avalanche photodiodes (APDs), as semiconductor optoelectronic devices with intrinsic carrier multiplication effects, can amplify weak light signals, significantly improving the system's signal-to-noise ratio and detection sensitivity. They represent an ideal technological path for achieving high-performance, low-light, and even single-photon-level infrared detection.

[0003] To achieve efficient detection in the mid-infrared band, selecting a suitable semiconductor material system is crucial. Although traditional HgCdTe (mercury cadmium telluride) materials have excellent optical properties, their poor crystal growth uniformity, the volatility of elemental mercury leading to poor device stability, and the complex and costly fabrication process limit their large-scale application.

[0004] In recent years, InAs / GaSb Type-II Superlattice (T2SL) materials based on group III-V compounds have emerged as a highly competitive solution for mid-wave infrared detection. This material system forms a unique band structure by alternately growing atomically thick InAs and GaSb layers. Its effective bandgap can be precisely controlled through "tailoring" the superlattice period thickness and layer thickness ratio, thus flexibly matching the target detection band. Compared to HgCdTe, InAs / GaSb Type-II superlattices offer advantages such as high effective electron mass, low Auger recombination rate, good material uniformity, and compatibility with mature group III-V semiconductor processes, laying the foundation for achieving high-performance, large-area, and uniform infrared focal plane arrays. However, applying InAs / GaSb Type-II superlattices to avalanche photodiodes (APDs) still faces a series of significant challenges. The core issue lies in effectively suppressing the dark current of the device under high operating bias voltages. The dark current of an APD mainly includes diffusion current, generation-recombination current, and tunneling current. In the high electric field region close to the breakdown voltage, band-to-band tunneling (BTBT) and trap-assisted tunneling (TAT) currents increase dramatically, severely overwhelming the weak avalanche gain signal, leading to a surge in device noise, a reduction in dynamic range, and even malfunction. Therefore, a new design scheme for mid-wave avalanche photodiodes is urgently needed. Summary of the Invention

[0005] In view of this, embodiments of the present invention provide a mid-wave avalanche photodiode and a mid-wave infrared detector to eliminate or improve one or more defects existing in the prior art, and solve the problems of insensitive response and weak gain of existing mid-wave avalanche photodiodes.

[0006] One aspect of the present invention provides a mid-wave avalanche photodiode, the mid-wave avalanche photodiode adopting a SAM structure, which includes a continuously arranged n-type doped type II superlattice bottom contact layer, a p-type doped multiplication layer, a p-type doped type II superlattice absorption layer, a p-type doped type II superlattice middle contact layer and a p-type doped top contact layer. The bottom contact layer, the absorption layer, and the middle contact layer of the type II superlattice are doped with InAs / GaSb, the multiplication layer is doped with AlInAsSb, and the top contact layer is doped with InAs. The thickness of the type-II superlattice absorber layer is 0.5~2μm, and the doping concentration is 1×10⁻⁶. 14 ~1×10 17 cm -3 ; The thickness of the multiplication layer is 0.5~0.8 μm, and the doping concentration is 1×10⁻⁶. 14 ~1×10 16 cm -3 ; The thickness of the bottom contact layer and the middle contact layer of the type-II superlattice are 0.1~0.4μm, and the doping concentration is 1×10⁻⁶. 18 ~5×10 18 cm -3 .

[0007] In some embodiments, the absorption layer is configured with multiple InAs and GaSb single-atom layer ratios to control the bandgap width and cover multiple mid-wave ranges.

[0008] In some embodiments, the thickness of the InAs single-atom layer and the GaSb single-atom layer is set to 0.3 nm; the InAs single-atom layer is set to 7 mL and the GaSb single-atom layer is set to 4 mL to cover the target response wavelength of 3~5 μm.

[0009] In some embodiments, the bottom contact layer of the type II superlattice, the absorption layer of the type II superlattice, and the middle contact layer of the type II superlattice are prepared by molecular beam epitaxy.

[0010] In some embodiments, the thickness of the bottom contact layer of the type-II superlattice is 0.2 μm, and the doping concentration is 5 × 10⁻⁶. 18 cm -3 ; The multiplication layer has a thickness of 0.6 μm and a doping concentration of 1 × 10⁻⁶. 15 cm -3 ; The type-II superlattice absorption layer has a thickness of 1 μm and a doping concentration of 1 × 10⁻⁶. 14 cm -3 ; The thickness of the intermediate contact layer of the type-II superlattice is 0.2 μm, and the doping concentration is 5 × 10⁻⁶. 18 cm -3 ; The top contact layer has a thickness of 0.02 μm and a doping concentration of 2 × 10⁻⁶. 19 cm -3 .

[0011] On the other hand, the present invention also provides a mid-wave infrared detector, comprising: An optical assembly, including optical lenses and filters, is used to introduce mid-wave infrared light in the 3-5μm band; The aforementioned mid-wave avalanche photodiode is used to perform photoelectric conversion on the mid-wave infrared light to obtain a photocurrent signal. The readout circuit is used to collect, integrate, and amplify the photocurrent signal.

[0012] In some embodiments, the mid-wave infrared detector further includes: the mid-wave infrared detector is vacuum-sealed and equipped with a cooler.

[0013] In some embodiments, the mid-wave infrared detector further includes a signal readout processing module for correcting and storing the photocurrent signal.

[0014] The mid-wave avalanche photodiode and mid-wave infrared detector described in this invention employ a separated absorption and multiplication structure. This scheme uses a bandgap-tunable InAs / GaSb type-two superlattice as the absorption layer and AlInAsSb with a high ionization coefficient as the multiplication layer, and precisely optimizes the thickness and doping concentration of each layer. The aim is to concentrate the high electric field within the multiplication layer to promote the avalanche effect, while simultaneously maintaining a low electric field in the absorption layer to suppress tunneling dark current. The structure of this invention achieves a gain of up to 85.2 at a bias voltage of 62V, with a complete optical response band covering 3~5μm and a responsivity of 3 A / W at 3.08μm. This simultaneously achieves the goals of high internal signal amplification capability and efficient mid-wave infrared photoelectric conversion, effectively improving the detector's sensitivity.

[0015] Additional advantages, objects, and features of the invention will be set forth in part in the description which follows, and will also become apparent in part to those skilled in the art upon studying the text, or may be learned by practice of the invention. The objects and other advantages of the invention can be realized and obtained by means of the structures specifically pointed out in the description and drawings.

[0016] Those skilled in the art will understand that the objectives and advantages achievable with the present invention are not limited to those specifically described above, and that the above and other objectives achievable with the present invention will become clearer from the following detailed description. Attached Figure Description

[0017] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, are not intended to limit the scope of the invention. The components in the drawings are not drawn to scale but are merely illustrative of the principles of the invention. For ease of illustration and description of certain parts of the invention, corresponding portions in the drawings may be enlarged, i.e., may appear larger relative to other components in an exemplary device actually manufactured according to the invention. In the drawings: Figure 1 This is a schematic diagram of the structure of a medium-wave avalanche photodiode according to an embodiment of the present invention.

[0018] Figure 2 This is a diagram showing the electric field intensity distribution under different multiplication layer thicknesses in the medium-wave avalanche photodiode described in this invention.

[0019] Figure 3 This is a diagram showing the voltage and breakdown voltage of the mid-wave avalanche photodiode described in this invention under different multiplication layer thicknesses.

[0020] Figure 4 This is a diagram showing the electric field intensity distribution under different doping concentrations of the multiplication layer in the medium-wave avalanche photodiode described in this invention.

[0021] Figure 5 This is a photoresponse curve of the mid-wave avalanche photodiode described in this invention.

[0022] Figure 6 This is a performance illustration of the mid-wave avalanche photodiode described in this invention.

[0023] Figure label: 1: Top contact layer; 2: Middle contact layer; 3: Absorption layer; 4: Multiplication layer; 5: Bottom contact layer. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments and accompanying drawings. Here, the illustrative embodiments and descriptions of this invention are used to explain the invention, but are not intended to limit the invention.

[0025] It should also be noted that, in order to avoid obscuring the invention with unnecessary details, only the structures and / or processing steps closely related to the solution according to the invention are shown in the accompanying drawings, while other details that are not closely related to the invention are omitted.

[0026] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, element, step, or component, but does not exclude the presence or addition of one or more other features, elements, steps, or components.

[0027] It should also be noted that, unless otherwise specified, the term "connection" in this article can refer not only to a direct connection, but also to an indirect connection involving an intermediary.

[0028] In the following description, embodiments of the invention will be illustrated with reference to the accompanying drawings. In the drawings, the same reference numerals represent the same or similar parts, or the same or similar steps.

[0029] Mid-wave infrared (MWIR) detectors are indispensable in military low-light imaging, long-range target detection, and civilian environmental monitoring and medical imaging. Avalanche photodiodes, with their internal carrier multiplication effect, can improve the signal-to-noise ratio in weak light detection and are core devices in this field. However, existing MWIR avalanche photodiodes suffer from excessively high dark current and unstable breakdown voltage characteristics, making it difficult to meet the requirements for detection limit and gain stability. InAs / GaSb type-II superlattices are key materials for MWIR avalanche photodiodes. Their bandgap can be precisely matched to the MWIR band by adjusting the periodic structure. Spatial separation of electron and hole wave functions can suppress Auger recombination and reduce dark current. Moreover, relying on mature III-V epitaxial technology, high uniformity and low defect growth can be achieved, resulting in significant advantages in device yield and consistency. In terms of structural design, this application adopts a "separated absorption multiplication layer" (SAM) structure to reduce tunneling current.

[0030] Specifically, one aspect of the present invention provides a mid-wave avalanche photodiode, such as... Figure 1 As shown, the mid-wave avalanche photodiode adopts a SAM structure, which includes a continuously arranged n-type doped type II superlattice bottom contact layer, p-type doped multiplication layer, p-type doped type II superlattice absorption layer, p-type doped type II superlattice middle contact layer and p-type doped top contact layer.

[0031] The bottom contact layer, absorber layer, and middle contact layer of the type II superlattice are doped with InAs / GaSb, the multiplication layer is doped with AlInAsSb, and the top contact layer is doped with InAs. The thickness of the absorber layer of the type II superlattice is 0.5~2μm, and the doping concentration is 1×10⁻⁶. 14 ~1×10 17 cm -3 The thickness of the multiplication layer is 0.5~0.8 μm, and the doping concentration is 1×10⁻⁶. 14 ~1×10 16 cm -3 The thickness of the bottom contact layer and the middle contact layer of the type-II superlattice are 0.1~0.4 μm, and the doping concentration is 1×10⁻⁶. 18 ~5×10 18 cm -3 .

[0032] Specifically, the scheme is a five-layer vertical heterostructure from bottom to top, with each layer having a clear functional division: the n-type doped type-II superlattice bottom contact layer serves as the cathode contact and electron collection layer of the device. A heavily doped InAs / GaSb superlattice is used to ensure low-resistance ohmic contacts. The p-type doped AlInAsSb multiplication layer is one of the core functional layers of the device; its wide bandgap and optimized thickness / doping are designed to withstand and concentrate the highest electric field, specifically responsible for the avalanche multiplication process of photogenerated carriers. The p-type doped type-II superlattice absorption layer is another core functional layer, employing a precisely tunable InAs / GaSb superlattice, responsible for efficiently absorbing infrared photons with wavelengths of 3~5μm and generating photogenerated carriers (electron-hole pairs). Its light doping and relatively thick design ensure sufficient light absorption. The p-type doped type-II superlattice middle contact layer is a crucial transition layer, serving both as a low-resistance pathway between the absorption layer and the top electrode, and participating in the modulation of the band structure at the interface between the absorption layer and the multiplication layer. The p-type doped InAs top contact layer serves as the anode contact of the device. By using heavily doped InAs, a high-quality p-type ohmic contact is achieved to facilitate current extraction.

[0033] AlInAsSb has several outstanding advantages as a multiplication region APD: its excess noise is extremely low, with a k-value as low as about 0.01; it has excellent high-temperature performance, requiring no low-temperature cooling and maintaining stable performance in the temperature range of 200~300K; it has strong bandgap adjustability, and the bandgap width can be flexibly adjusted by changing the Al composition. The wide bandgap characteristic can suppress interband tunneling under high electric fields in the multiplication region to reduce dark current, while also being adaptable to the detection requirements of different infrared bands.

[0034] The working principle of this invention's mid-wave avalanche photodiode is based on two core physical concepts: separation of absorption and multiplication space, and zonal management of electric field. Functional separation refers to the absorption of infrared light in the absorption layer, generating primary photogenerated carriers, primarily electrons. These carriers are injected into adjacent multiplication layers. Because the multiplication layer is subjected to an extremely high electric field, typically close to the breakdown field, the injected carriers undergo violent collisional ionization, producing an avalanche effect and achieving exponential current amplification, i.e., gain. Electric field control refers to the careful design of the doping concentration and thickness of each layer. For example, the multiplication layer is moderately lightly doped to broaden the depletion region, while the absorption layer is lightly doped to reduce the electric field. The SAM structure ensures that the depletion region under reverse bias mainly extends towards the multiplication layer, thus strictly confining the high electric field within the wide bandgap multiplication layer. Simultaneously, the absorption layer is subjected to a relatively low electric field. This "high-low" electric field distribution ensures both the high gain of the multiplication layer and significantly suppresses the interband tunneling dark current generated by the high electric field in the narrow bandgap absorption layer.

[0035] In some embodiments, the bottom contact layer, the absorber layer, and the intermediate contact layer of the type-II superlattice are fabricated using molecular beam epitaxy. In some embodiments, the bottom contact layer of the type-II superlattice has a thickness of 0.2 μm and a doping concentration of 5 × 10⁻⁶. 18 cm -3 The multiplication layer has a thickness of 0.6 μm and a doping concentration of 1 × 10⁻⁶. 15 cm -3 The thickness of the type-II superlattice absorber layer is 1 μm, and the doping concentration is 1 × 10⁻⁶. 14 cm -3 The thickness of the intermediate contact layer in the type-II superlattice is 0.2 μm, and the doping concentration is 5 × 10⁻⁶. 18 cm -3 The top contact layer has a thickness of 0.02 μm and a doping concentration of 2 × 10⁻⁶. 19 cm -3 .

[0036] The technical solution of this embodiment achieves a significant improvement in overall performance by employing a Separated Absorption and Multiplication (SAM) structure and synergistically optimizing the materials, thickness, and doping of the InAs / GaSb superlattice absorber layer and the AlInAsSb multiplication layer. Its core effect lies in simultaneously achieving high internal gain and low noise operation. By precisely confining the high electric field to the wide bandgap multiplication layer, the device achieves an avalanche gain of up to 85.2% at a 62V bias, while simultaneously forcing the narrow bandgap absorber layer to operate in a low electric field state, thereby effectively suppressing tunneling dark current from a physical mechanism. Furthermore, by utilizing the tunable bandgap characteristic of the type-II superlattice, the device achieves a peak responsivity of 3A / W at 3.08μm in the 3~5μm mid-wave infrared band, realizing high-efficiency photoelectric conversion. The optimization of the multiplication layer thickness and doping, such as 0.6μm and 1×10⁻⁶, further enhances its performance. 15 cm -3 This allows key parameters such as breakdown voltage to have good controllability, ultimately creating a mid-wave infrared detection solution that combines high sensitivity, low noise, and wide-spectrum response.

[0037] In some embodiments, the absorption layer is configured with multiple InAs and GaSb single-atom layer ratios to control the bandgap width and cover multiple mid-wave ranges.

[0038] In some embodiments, the thickness of the InAs single-atom layer and the GaSb single-atom layer is set to 0.3 nm; the InAs single-atom layer is set to 7 mL and the GaSb single-atom layer is set to 4 mL to cover the target response wavelength of 3~5 μm.

[0039] On the other hand, the present invention also provides a mid-wave infrared detector, comprising: an optical device group, a mid-wave avalanche photodiode as described above, and a readout circuit. The optical device group includes an optical lens and a filter to guide mid-wave infrared light in the 3~5μm band; the mid-wave avalanche photodiode is used to perform photoelectric conversion on the mid-wave infrared light to obtain a photocurrent signal; the readout circuit is used to collect, integrate, and amplify the photocurrent signal.

[0040] This embodiment constructs a complete mid-wave infrared detection system. By systematically integrating high-sensitivity core optoelectronic devices with front-end optics and back-end readout circuitry, high-performance detection of infrared signals in the 3-5μm band is achieved. The optical device group is responsible for filtering and introducing infrared radiation in the target band, providing a clean optical signal input to the system. The mid-wave avalanche photodiode with SAM structure described in this invention serves as the core conversion unit. Utilizing its high gain and low noise characteristics, it efficiently converts the weak optical signal into an amplified photocurrent signal, significantly improving the system's signal-to-noise ratio and detection sensitivity. The readout circuit follows closely behind, responsible for collecting, integrating, and amplifying the primary electrical signal, providing a stable and robust signal foundation for subsequent image processing or data analysis. This scheme embodies the end-to-end optimization concept from optical input to electrical signal output, allowing the overall performance of the detector to be fully utilized.

[0041] In some embodiments, the mid-wave infrared detector further includes a vacuum Dewar cascade and a cryostat. This embodiment employs a vacuum Dewar cascade for the mid-wave infrared detector, creating a high-vacuum, heat-insulating environment that significantly reduces external heat load. An integrated cryostat, typically a Stirling or pulse tube cryostat, is then used to actively and stably cool the entire focal plane array to deep cryogenic temperatures. This combined design aims to physically suppress dark currents caused by temperature in the detector chip, reduce thermal noise, and improve carrier lifetime and mobility, thereby ensuring that high-gain, low-noise characteristics are fully realized at the system level. Ultimately, this achieves high sensitivity and excellent signal-to-noise ratio for the detector, representing a typical technical path for supporting strategic-level high-performance detector specifications.

[0042] In some embodiments, the mid-wave infrared detector further includes a signal readout processing module for correcting and storing the photocurrent signal. In this embodiment, the signal readout processing module intervenes after the readout circuit completes front-end amplification, performing critical back-end algorithm processing on the initially converted photocurrent signal. The correction function typically refers to non-uniformity correction (NUC), used to compensate for inter-pixel response differences caused by manufacturing processes, as well as for bad pixel repair and temporal noise suppression, to eliminate fixed pattern noise and transient interference; while the storage function means that the module integrates buffer or frame storage capabilities, providing necessary support for continuous signal reading, multi-frame processing, or asynchronous data transmission with external systems.

[0043] The present invention will now be described with reference to a specific embodiment: This invention proposes a SAM structure avalanche photodiode for mid-wave infrared detection, such as... Figure 1 As shown, the device structure uses an InAs / GaSb superlattice structure as the bottom contact layer, absorption layer, and intermediate contact layer, AlInAsSb as the multiplication layer, and InAs as the top contact layer. The absorption layer has a doping concentration of 1×10⁻⁶. 14 cm -3 The doping concentration of the multiplication layer is 1×10⁻⁶. 15 cm -3 The doping concentration of the bottom and middle contact layers of the type-II superlattice is 5 × 10⁻⁶. 18 cm -3 The doping concentration of the top contact layer of InAs is 2×10⁻⁶. 19 cm -3 The invention mainly separates the absorption layer and the multiplication layer, and controls the thickness and doping to increase the electric field strength of the multiplication layer, making it easier for electrons to ionize in the multiplication layer and improving device gain.

[0044] Electric field distribution at different thicknesses of the multiplication layer is as follows Figure 2 As shown. By Figure 2 It can be seen that when the thickness of the multiplication layer increases from 0.5 μm to 0.8 μm, the peak electric field intensity increases from 6.4 × 10⁻⁶ μm. V / cm decreased to 6.0× V / cm, which affects the impact ionization of charge carriers, thus reducing avalanche gain. The effect of different multiplication layer thicknesses on punch-through voltage and breakdown voltage is as follows: Figure 3 As shown, the device's punch-through voltage increased from 23V to 37V, and its breakdown voltage increased from 53V to 66V. Increasing the thickness of the multiplication region requires a larger bias voltage to achieve the same multiplication effect, resulting in a significant increase in both punch-through and breakdown voltages. Therefore, the multiplication layer thickness was set to 0.6μm.

[0045] Electric field distribution of multiplication layer with different doping: Figure 4 As shown, increasing the doping concentration of the dynamometer layer significantly increases the space charge density. According to the Poisson equation, this increases the slope of the adsorption dynamometer electric field, leading to greater randomness in carrier multiplication during avalanche multiplication and thus affecting device performance. Therefore, the dynamometer layer doping concentration is set to 1×10⁻⁶. 15 cm -3 .

[0046] The optical response curve of the device is as follows Figure 5 As shown. By Figure 5 It can be seen that the device's response band covers 3-5 μm, with a maximum photoresponsivity of 3 A / W at 3.08 μm. The device's IV characteristic curves and gain are shown below.Figure 6 As shown, with the increase of the applied bias voltage, the photocurrent changes from... A increased to A. When the bias voltage is 62V, the device gain is 85.2.

[0047] Furthermore, this embodiment provides a preferred embodiment of an avalanche photodiode, comprising the following structure: a bottom contact layer, a multiplication layer, an absorption layer, an intermediate contact layer, and a top contact layer. The bottom contact layer is an InAs / GaSb superlattice structure with a thickness of 0.2 μm, n-type doped, and a doping concentration of 5 × 10⁻⁶. 18 cm -3 The multiplication layer is an AlInAsSb structure with a thickness of 0.6 μm, p-type doped, and a doping concentration of 1×10⁻⁶. 15 cm -3 The absorption layer is an InAs / GaSb superlattice structure with a thickness of 1 μm, p-type doped, and a doping concentration of 1 × 10⁻⁶. 14 cm -3 The intermediate contact layer is an InAs / GaSb superlattice structure with a thickness of 0.2 μm, p-type doped, and a doping concentration of 5 × 10⁻⁶. 18 cm -3 The top contact layer is an InAs structure with a thickness of 0.02 μm, p-type doped, and a doping concentration of 2 × 10⁻⁶. 19 cm -3 .like Figure 6 As shown, in this embodiment, the photocurrent increases from 10^(-9) A to 10^(-6) A as the applied bias voltage increases. When the bias voltage reaches 32V, the device enters the linear operating region and breaks down when the bias voltage increases to 62V. When the device enters the linear operating region, the gain is 52, because photogenerated carriers gain enough energy to reach the multiplication region, where they undergo avalanche multiplication through collisional ionization, resulting in a significant increase in gain. When the bias voltage reaches 62V and the device breaks down, the gain rises to 85.2.

[0048] In summary, the mid-wave avalanche photodiode and mid-wave infrared detector described in this invention employ a separated absorption and multiplication structure. This scheme utilizes a bandgap-tunable InAs / GaSb type-two superlattice as the absorption layer and AlInAsSb with a high ionization coefficient as the multiplication layer, precisely optimizing the thickness and doping concentration of each layer. The aim is to concentrate the high electric field within the multiplication layer to promote the avalanche effect, while simultaneously maintaining a low electric field in the absorption layer to suppress tunneling dark current. The structure of this invention achieves a gain as high as 85.2 at a 62V bias, with a complete optical response band covering 3–5 μm and a responsivity of 3 A / W at 3.08 μm. This simultaneously achieves the goals of high internal signal amplification capability and efficient mid-wave infrared photoelectric conversion, effectively improving the detector's sensitivity.

[0049] Those skilled in the art will understand that the exemplary components, systems, and methods described in conjunction with the embodiments disclosed herein can be implemented in hardware, software, or a combination of both. Whether implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this invention. When implemented in hardware, it can be, for example, electronic circuits, application-specific integrated circuits (ASICs), appropriate firmware, plug-ins, function cards, etc. When implemented in software, the elements of this invention are programs or code segments used to perform the desired tasks. The programs or code segments can be stored in a machine-readable medium or transmitted over a transmission medium or communication link via data signals carried in a carrier wave.

[0050] It should be clarified that the present invention is not limited to the specific configurations and processes described above and shown in the figures. For the sake of brevity, detailed descriptions of known methods are omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of the present invention is not limited to the specific steps described and shown. Those skilled in the art can make various changes, modifications, and additions, or change the order of steps, after understanding the spirit of the present invention.

[0051] In this invention, features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, and / or combined with or in place of features of other embodiments.

[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, various modifications and variations of the embodiments of the present invention are possible. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A medium-wave avalanche photodiode, characterized in that, The mid-wave avalanche photodiode adopts a SAM structure, which includes a continuously arranged n-type doped type II superlattice bottom contact layer, p-type doped multiplication layer, p-type doped type II superlattice absorption layer, p-type doped type II superlattice middle contact layer and p-type doped top contact layer. The bottom contact layer, the absorption layer, and the middle contact layer of the type II superlattice are doped with InAs / GaSb, the multiplication layer is doped with AlInAsSb, and the top contact layer is doped with InAs. The thickness of the type-II superlattice absorber layer is 0.5~2μm, and the doping concentration is 1×10⁻⁶. 14 ~1×10 17 cm -3 ; The thickness of the multiplication layer is 0.5~0.8 μm, and the doping concentration is 1×10⁻⁶. 14 ~1×10 16 cm -3 ; The thickness of the bottom contact layer and the middle contact layer of the type-II superlattice are 0.1~0.4μm, and the doping concentration is 1×10⁻⁶. 18 ~5×10 18 cm -3 .

2. The mid-wave avalanche photodiode according to claim 1, characterized in that, The absorption layer is configured with multiple InAs and GaSb single-atom layer ratios to control the bandgap width and cover multiple mid-wave ranges.

3. The mid-wave avalanche photodiode according to claim 2, characterized in that, The thickness of the InAs single-atom layer and the GaSb single-atom layer is set to 0.3 nm; the InAs single-atom layer is set to 7 mL and the GaSb single-atom layer to 4 mL, so as to cover the target response wavelength of 3~5 μm.

4. The mid-wave avalanche photodiode according to claim 1, characterized in that, The bottom contact layer of the type II superlattice, the absorption layer of the type II superlattice, and the middle contact layer of the type II superlattice are prepared by molecular beam epitaxy.

5. The mid-wave avalanche photodiode according to claim 1, characterized in that, The bottom contact layer of the type-II superlattice has a thickness of 0.2 μm and a doping concentration of 5 × 10⁻⁶. 18 cm -3 ; The multiplication layer has a thickness of 0.6 μm and a doping concentration of 1 × 10⁻⁶. 15 cm -3 ; The type-II superlattice absorption layer has a thickness of 1 μm and a doping concentration of 1 × 10⁻⁶. 14 cm -3 ; The thickness of the intermediate contact layer of the type-II superlattice is 0.2 μm, and the doping concentration is 5 × 10⁻⁶. 18 cm -3 ; The top contact layer has a thickness of 0.02 μm and a doping concentration of 2 × 10⁻⁶. 19 cm -3 .

6. A mid-wave infrared detector, characterized in that, include: An optical assembly, including optical lenses and filters, is used to introduce mid-wave infrared light in the 3-5μm band; The mid-wave avalanche photodiode as described in any one of claims 1 to 5 is used to perform photoelectric conversion on the mid-wave infrared light to obtain a photocurrent signal; The readout circuit is used to collect, integrate, and amplify the photocurrent signal.

7. The mid-wave infrared detector according to claim 6, characterized in that, Also includes: The mid-wave infrared detector is vacuum-sealed and equipped with a cooler.

8. The mid-wave infrared detector according to claim 6, characterized in that, It also includes a signal readout processing module for correcting and storing the photocurrent signal.

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