Multi-spectral InGaAs avalanche focal plane detector and manufacturing method thereof

Abstract

The application discloses a kind of multispectral InGaAs avalanche focal plane detector and manufacturing method, detector uses back-illumination structure, multispectral integrated optical filter is set in the light entrance surface of detector by ceramic support;When manufacturing, InP substrate is thinned by mechanical grinding;Chemical etching process is used, and remaining InP substrate and InP etching sacrificial layer, InGaAs etching sacrificial layer are removed in turn;Prepare by Fabry-Perot narrow-band filter unit on transparent optical substrate, and multispectral integrated optical filter is installed on indium gallium arsenide avalanche focal plane module InP contact layer side by ceramic support.The application is combined with avalanche multiplication structure and multispectral integrated optical filter array, and wide-spectrum light response and multispectral selective detection can be realized in the range of visible light to near-infrared band, and single-photon level sensitivity detection is realized, and overall dynamic range can reach 120 dB and above, and can be used in photon counting imaging and low-light night vision, hyperspectral imaging detection and other application fields.

Description

Technical Field

[0001] This invention relates to the field of semiconductor chip manufacturing technology, and in particular to a multi-band InGaAs avalanche focal plane detector and its manufacturing method. Background Technology

[0002] InGaAs focal plane detectors, which are lattice-matched with InP substrates, typically have a spectral response range of 900–1700 nm. They offer advantages such as near-room temperature operation, high detectivity, high uniformity, stable performance, and relatively low cost. They are of great value in short-wave infrared imaging through smoke, fog, and dust, and are an important type of device in the field of short-wave infrared detection.

[0003] Compared to traditional PIN-based InGaAs focal plane arrays, InGaAs avalanche focal plane array detectors utilize the collisional ionization multiplication effect within avalanche photodiode pixels to achieve high-gain photoelectric conversion within the pixel. When operating in Geiger mode, the charge carriers generated by a single photon can trigger a self-sustaining avalanche, generating a large-amplitude electrical signal, thus achieving photon-level sensitivity. Furthermore, photon-counting imaging detectors based on InGaAs Geiger avalanche focal plane arrays are not limited by the full-well capacity of traditional image sensors, enabling them to adapt to wide dynamic range imaging requirements from strong light to extremely weak light environments. Therefore, InGaAs avalanche focal plane arrays combine high sensitivity, high-speed response, large dynamic range, and weak-light imaging capabilities, making them promising candidates for next-generation active / passive dual-mode, multi-functional, multi-band infrared focal plane array detectors.

[0004] In passive low-light imaging applications, natural low-light radiation such as moonlight, atmospheric glow, and starlight covers the visible to short-wave infrared bands. Ambient photon resources are particularly abundant in the 400–900 nm visible and near-infrared range. However, conventional InGaAs focal plane arrays only cover approximately 900–1700 nm, failing to fully utilize the visible and near-infrared ambient photons in the 400–900 nm range, thus limiting their photon utilization efficiency and imaging quality in low-light night vision scenarios. If the response range of the InGaAs avalanche focal plane array can be extended from the conventional short-wave infrared to 400–1700 nm, ambient photons in the visible, near-infrared, and short-wave infrared bands can be utilized simultaneously. Combined with avalanche gain and photon counting mechanisms, higher sensitivity and a wider dynamic range can be achieved in low-light imaging, resulting in clearer images and richer target detail information.

[0005] Hyperspectral imaging can simultaneously acquire two-dimensional spatial information and one-dimensional spectral information of a target, forming a three-dimensional data cube. Different materials exhibit different reflection, absorption, and transmission characteristics in the visible to near-infrared bands, displaying distinctive spectral fingerprints. Therefore, wide-spectrum detection capabilities are beneficial for acquiring richer target spectral information, improving target recognition, material differentiation, camouflage identification, and complex scene perception capabilities. However, hyperspectral imaging typically requires dividing the incident light into multiple narrow spectral bands using beam-splitting elements such as gratings, prisms, or narrowband filters, resulting in a significant reduction in photon flux within each spectral band. Especially in scenarios such as low-light conditions at night, long-range detection, and low-reflectivity target identification, traditional PIN-type focal plane arrays are easily limited by insufficient weak light signals, leading to a decrease in image signal-to-noise ratio, loss of details in weak targets, and incomplete spectral information.

[0006] Currently, there are some research reports on visible extended InGaAs focal plane arrays based on PIN pixels. For example, Sensors Unlimited in the United States has fabricated a visible extended InGaAs / InP PIN focal plane array detector based on InP substrate lift-off technology and achieved broadband night vision imaging; SCD in Israel has also reported a similar visible extended InGaAs PIN focal plane array device. However, such devices lack avalanche gain and photon counting capabilities, making it difficult to meet the requirements for photon-level sensitive detection; at the same time, they are usually a single broadband response mode, making it difficult to separate and acquire different spectral information within the same focal plane, thus limiting the ability to identify targets and extract spectral information.

[0007] For InGaAs avalanche focal plane arrays, due to the presence of in-pixel gain, extending the spectral response range from 900-1700 nm to cover the visible light band (400-1700 nm) and integrating multi-spectral filters would allow for more efficient utilization of the photon energy reflected from the target. This would leverage multiple advantages, including in-pixel gain, broad spectral response, multi-spectral discrimination, photon counting capabilities, and a large dynamic range. This would enable photon-level sensitivity detection across a wide spectral range, resulting in clearer images and more target information, significantly enhancing night vision imaging capabilities and target recognition accuracy. However, because the working principle, device structure, and fabrication process of InGaAs avalanche focal plane arrays are more complex than those of PIN focal plane arrays, there are currently no InGaAs avalanche focal plane array detectors based on avalanche photodiode pixels and integrated with multi-spectral filters. There are difficulties in achieving visible response extension and multi-spectral filter integration technology. Technological innovation is needed in the structural design of avalanche detector image components, spectral extension process, and multi-spectral filter integration process to achieve photon-level sensitive detection in multiple spectral bands over a wide spectral range and ensure the large dynamic range and operational stability of the device. Summary of the Invention

[0008] The purpose of this invention is to provide a multi-band InGaAs avalanche focal plane detector and its fabrication method, which overcomes the shortcomings of existing InGaAs focal plane detectors that can only cover the approximately 900–1700 nm wavelength band and cannot fully utilize visible and near-infrared environmental photons in the 400–900 nm range, thus limiting their photon utilization efficiency and imaging quality in low-light night vision scenarios.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A multi-band InGaAs avalanche focal plane detector is composed of a multi-band integrated filter and an InGaAs avalanche focal plane detector. The InGaAs avalanche focal plane detector includes a heavily doped InP contact layer, an InGaAs absorption layer, a band transition layer, a charge layer, an avalanche layer, a P-type electrode contact layer, an indium pillar, and a Si readout circuit. The multi-band integrated filter is mounted on the heavily doped InP contact layer via a ceramic support.

[0011] The InGaAs avalanche focal plane detector has a pixel array size of M×N; correspondingly, the multi-band integrated filter is a microstructure array filter composed of multiple filter units, each filter unit being sequentially divided along the column direction of the pixel array and covering the corresponding pixel subarray.

[0012] The multi-band integrated filter is composed of multiple Fabry-Perot narrowband filter units, each of which includes a lower high-reflectivity film, a resonant cavity layer, and an upper high-reflectivity film.

[0013] The lower and upper high-reflectivity films are formed by alternating stacking of high-refractive-index dielectric films and low-refractive-index dielectric films. The high-refractive-index dielectric films are TiO2, Ta2O5, ZnS, or Si3N4, and the low-refractive-index dielectric films are SiO2, MgF2, or Al2O3. The resonant cavity layer is a transparent dielectric layer of SiO2, MgF2, Al2O3, Si3N4, Ta2O5, TiO2, or ZnS. The resonant cavity layers in different narrowband filter units have different optical thicknesses to achieve different center transmission wavelengths.

[0014] The multi-band integrated filter has 2 to 32 spectral channels, covering a spectral range of 400 to 1700 nm, and the filter bandwidth of each spectral channel is 10 to 100 nm.

[0015] The thickness of the heavily doped InP contact layer is 10–80 nm, the doping type is N, and the doping concentration is ≥1×10⁻⁶. 18 cm -3The heavily doped InP contact layer also serves as the N-type electrode contact layer for the InGaAs avalanche focal plane detector pixel; the InGaAs avalanche focal plane detector operates in Geiger mode and employs a photon counting operating system.

[0016] The height of the ceramic support is 10–100 μm.

[0017] The total number of filter units in the multi-band integrated filter is Y, where the pixel area covered by the i-th filter is M× Let i = 1, 2, ..., Y, and satisfy... Furthermore, the coverage areas of all filter units are arranged sequentially in the column direction without overlapping, and satisfy the following conditions: This constitutes a multi-spectral filter integrated structure that completely covers the M×N pixel array.

[0018] A method for fabricating a multi-band InGaAs avalanche focal plane array detector as described in any of the preceding claims includes the following steps:

[0019] S1. Fabricate an InGaAs avalanche focal plane module interconnected with a Si readout circuit. The InGaAs avalanche focal plane module includes an InP substrate, an InP etched sacrificial layer, an InGaAs etched sacrificial layer, a heavily doped InP contact layer, an InGaAs absorber layer, a band transition layer, a charge layer, an avalanche layer, and a P-type electrode contact layer. The Si readout circuit is interconnected with the InGaAs avalanche focal plane module through an indium pillar.

[0020] S2. The InP substrate is mechanically thinned to a remaining thickness of 50 μm to 100 μm. Then, a two-step selective chemical etching process is used. First, the remaining InP substrate and the InP etching sacrificial layer are removed using an etching solution containing HCl:H3PO4, and the etching stops at the InGaAs etching sacrificial layer. Then, the InGaAs etching sacrificial layer is removed using an etching solution containing tartaric acid:H2O2, and the etching stops at the heavily doped InP contact layer, thus obtaining the InGaAs avalanche focal plane detector.

[0021] S3, supported by a transparent optical substrate, a lower high-reflectivity film composed of alternating high and low refractive index dielectric films is deposited, and a resonant cavity layer is formed on the lower high-reflectivity film;

[0022] S4. The thickness of the resonant cavity layer in different regions is controlled by regional photolithography and selective etching or step-by-step deposition process. Then, a high-reflectivity film composed of alternating high and low refractive index dielectric films is deposited, so that FP narrowband filter units with different central transmission wavelengths are formed in different regions, and multi-spectral integrated filter is obtained.

[0023] S5, the multi-band integrated filter is mounted on the heavily doped InP contact layer on the incident surface side of the InGaAs avalanche focal plane detector through a ceramic bracket, and different narrowband filter units are set to correspond to the detector pixel area to achieve multi-band selective transmission and detection of incident light.

[0024] The InP etch sacrificial layer has a thickness of 5 nm to 10 μm, the InGaAs etch sacrificial layer has a thickness of 5 nm to 5 μm, and the heavily doped InP contact layer has a thickness of 10 nm to 100 nm.

[0025] The heavily doped InP contact layer serves as both a selective etching stop layer and an N-type electrode contact layer for the InGaAs avalanche focal plane detector pixel; the InGaAs absorption layer is adjacent to the heavily doped InP contact layer to reduce the absorption of InP 400 nm to 925 nm visible and near-infrared photons and improve the incident light absorption efficiency; the charge layer is InP, the avalanche layer is InP, and the detector doping structure is P-on-N.

[0026] In view of the above technical features, the present invention has the following beneficial effects: 1. The present invention is a photon-level sensitive indium gallium arsenide (IGaAs) multi-spectral imaging detector; 2. The present invention achieves nanoscale precise control of the InP contact layer through a double sacrificial layer selective etching process, effectively reducing material damage; 3. The detector combines an IGaAs avalanche multiplication structure with a multi-spectral integrated filter array, enabling broadband optical response and multi-spectral selective detection in the visible to near-infrared range. Simultaneously, relying on the high-gain characteristics of the avalanche layer, the detector can achieve single-photon-level sensitivity detection, with an overall dynamic range of 120dB or higher, possessing large dynamic range and high signal-to-noise ratio imaging capabilities, suitable for photon counting imaging and applications such as low-light night vision and hyperspectral imaging detection; 4. The present invention employs an epitaxial structure combining an InP etched sacrificial layer, an InGaAs etched sacrificial layer, and an InP contact layer, matched with a two-step selective chemical etching process, achieving high-precision, low-damage removal of the InP substrate. By controlling the thickness of the InP contact layer at the nanometer level, its absorption of visible and near-infrared photons in the 400 nm–925 nm range can be reduced, enabling the InGaAs avalanche focal plane to achieve a broad spectral response capability of 400 nm–1700 nm. 5. This invention integrates a multi-band filter array on the incident surface side of the broad-spectrum InGaAs avalanche focal plane, allowing different narrowband filter units to correspond to different pixel subarrays, thereby achieving selective detection of multiple target spectral bands within a single focal plane. Compared to traditional single broadband response focal planes, this structure can simultaneously acquire multi-band information during imaging, improving target spectral feature extraction capabilities and scene information dimensions. 6. The multi-band integrated filter described in this invention can adopt an FP narrowband filter structure. By adjusting the optical thickness of the resonant cavity layer in different filter units, different center transmission wavelengths can be achieved. Through the film system design of the upper and lower high-reflectivity films, the filter bandwidth, peak transmittance, and out-of-band suppression capability can be adjusted. This structure facilitates selective transmission of multi-spectral light signals in the visible to near-infrared range, and establishes a corresponding relationship with the lower pixel sub-array. 7. This invention combines the internal gain, photon counting capability, and broadband response capability of the InGaAs avalanche focal plane array with the integration capability of multi-spectral filters, enabling photon-level sensitivity detection across multiple spectral bands. This detector can fully utilize visible to short-wave infrared photons in low-light environments such as moonlight, atmospheric glow, and starlight, improving the quality of low-light night vision imaging. Simultaneously, the parallel acquisition of multi-spectral information helps enhance target recognition, material differentiation, camouflage identification, and hyperspectral scene perception capabilities. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the multi-band InGaAs avalanche focal plane detector of the present invention.

[0028] Figure 2This is a schematic diagram of the InGaAs / InP avalanche focal plane array structure of the present invention.

[0029] Figure 3 This is a top view of the InGaAs avalanche focal plane of the present invention.

[0030] Figure 4 This is a top view of the multi-band InGaAs avalanche focal plane detector of the present invention.

[0031] Figure 5 This is a schematic diagram of the material structure of the InGaAs / InP avalanche focal plane in Embodiment 1 of the present invention.

[0032] Figure 6 This is a schematic diagram of the structure of the multi-band InGaAs avalanche focal plane detector in Embodiment 1 of the present invention.

[0033] In the figure: 1—Multi-band integrated filter; 2—Ceramic support; 3—InP substrate; 4—InP etched sacrificial layer; 5—InGaAs etched sacrificial layer; 6—Heavily doped InP contact layer; 7—InGaAs absorption layer; 8—Band transition layer; 9—Charge layer; 10—Avalanche layer; 11—P-type electrode contact layer.

[0034] 12—Indium pillar; 13—Si readout circuit. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these drawings and embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that some components well-known to those skilled in the art but not related to the main content of the present invention may be omitted in the drawings or description. Additionally, for ease of description, some components in the drawings may be omitted, enlarged, or reduced, but this does not represent the actual size or complete structure of the product.

[0036] A multi-band InGaAs avalanche focal plane detector, such as Figure 1 As shown, it is composed of a multi-band integrated filter 1 and an InGaAs avalanche focal plane detector. The InGaAs avalanche focal plane detector includes a heavily doped InP contact layer 6, an InGaAs absorption layer 7, a band transition layer 8, a charge layer 9, an avalanche layer 10, a P-type electrode contact layer 11, an indium pillar 12, and a Si readout circuit 13. The multi-band integrated filter 1 is mounted on the heavily doped InP contact layer 6 on the light-incident side of the InGaAs avalanche focal plane detector via a ceramic support 2.

[0037] like Figure 3 As shown, the pixel array size of the InGaAs avalanche focal plane detector is M×N; correspondingly, as Figure 4As shown, the multi-band integrated filter 1 is a microstructure array filter composed of multiple filter units. Each filter unit is divided sequentially along the column direction of the pixel array and covers the corresponding pixel sub-array.

[0038] The multi-band integrated filter 1 has a total of Y filter units, where the pixel area covered by the i-th filter is M× Let i = 1, 2, ..., Y, and satisfy... Furthermore, the coverage areas of all filter units are arranged sequentially in the column direction without overlapping, and satisfy the following conditions: This constitutes a multi-spectral filter integrated structure that completely covers the M×N pixel array.

[0039] Each filter corresponds to a different target spectral band, used to achieve multi-band selective transmission of incident light in a wide visible-near infrared range.

[0040] Preferably, the multi-band integrated filter 1 is composed of multiple Fabry-Perot narrowband filter units, each of which includes a lower high-reflectivity film, a resonant cavity layer, and an upper high-reflectivity film.

[0041] The lower and upper high-reflectivity films are formed by alternating stacking of high-refractive-index dielectric films and low-refractive-index dielectric films. The high-refractive-index dielectric films are TiO2, Ta2O5, ZnS, or Si3N4, and the low-refractive-index dielectric films are SiO2, MgF2, or Al2O3. The resonant cavity layer is a transparent dielectric layer of SiO2, MgF2, Al2O3, Si3N4, Ta2O5, TiO2, or ZnS. The resonant cavity layers in different narrowband filter units have different optical thicknesses to achieve different center transmission wavelengths.

[0042] In one embodiment, the resonant cavity layer is made of SiO2 transparent dielectric material. The thickness of the resonant cavity layer in different Fabry-Perot narrowband filter units is 150 nm to 600 nm, corresponding to narrowband filtering with different center transmission wavelengths in the range of 400 nm to 1700 nm. Specifically, when the thickness of the resonant cavity layer is 154 nm, 182 nm, 223 nm, 291 nm, 364 nm, 449 nm, 531 nm and 582 nm, it corresponds to center transmission wavelengths of 450 nm, 532 nm, 650 nm, 850 nm, 1064 nm, 1310 nm, 1550 nm and 1700 nm, respectively.

[0043] The multi-band integrated filter 1 has 2 to 32 spectral channels, covering a spectral range of 400 to 1700 nm, and the filter bandwidth of each spectral channel is 10 to 100 nm.

[0044] The multi-band integrated filter 1 is independently fabricated with a transparent optical substrate as support, and is set on the light-incident surface side of the InGaAs avalanche focal plane detector by a ceramic support 2, so that each narrowband filter unit is aligned with the corresponding pixel sub-array below. The height of the ceramic support 2 is 10-100 μm, so that the gap between the multi-band integrated filter 1 and the InGaAs avalanche focal plane detector is 10-100 μm.

[0045] The thickness of the heavily doped InP contact layer 6 is 10–80 nm, the doping type is N, and the doping concentration is ≥1×10⁻⁶. 18 cm -3 The heavily doped InP contact layer 6 also serves as the N-type electrode contact layer for the InGaAs avalanche focal plane detector pixel; the InGaAs avalanche focal plane detector operates in Geiger mode and employs a photon counting operating system.

[0046] A method for fabricating a multi-band InGaAs avalanche focal plane detector as described in any of the preceding claims, comprising the following steps:

[0047] S1, fabricate an InGaAs avalanche focal plane array module interconnected with the Si readout circuit 13, such as Figure 2 As shown, the InGaAs avalanche focal plane module includes an InP substrate 3, an InP etched sacrificial layer 4, an InGaAs etched sacrificial layer 5, a heavily doped InP contact layer 6, an InGaAs absorber layer 7, a band transition layer 8, a charge layer 9, an avalanche layer 10, and a P-type electrode contact layer 11. The Si readout circuit 13 is interconnected with the InGaAs avalanche focal plane module through an indium pillar 12.

[0048] The InP etch sacrificial layer 4 has a thickness of 5 nm to 10 μm, the InGaAs etch sacrificial layer 5 has a thickness of 5 nm to 5 μm, and the heavily doped InP contact layer 6 has a thickness of 10 nm to 100 nm.

[0049] S2, the InP substrate 3 is mechanically thinned by grinding to a remaining thickness of 50 μm to 100 μm; then a two-step selective chemical etching process is used. First, the remaining InP substrate 3 and the InP etching sacrificial layer 4 are removed using an etching solution containing HCl and H3PO4, and the etching stops at the InGaAs etching sacrificial layer 5; then, the InGaAs etching sacrificial layer 5 is removed using an etching solution containing tartaric acid and H2O2, and the etching stops at the heavily doped InP contact layer 6, thus obtaining the InGaAs avalanche focal plane detector.

[0050] S3, supported by a transparent optical substrate, a lower high-reflectivity film composed of alternating high and low refractive index dielectric films is deposited, and a resonant cavity layer is formed on the lower high-reflectivity film;

[0051] S4. The thickness of the resonant cavity layer in different regions is controlled by regional photolithography and selective etching or step-by-step deposition process. Then, a high-reflectivity film composed of alternating high and low refractive index dielectric films is deposited, so that FP narrowband filter units with different central transmission wavelengths are formed in different regions, and multi-spectral integrated filter 1 is obtained.

[0052] S5, the multi-band integrated filter 1 is mounted on the heavily doped InP contact layer 6 on the light incident surface side of the InGaAs avalanche focal plane detector through the ceramic support 2, and different narrowband filter units are set to correspond to the detector pixel area to achieve multi-band selective transmission and detection of incident light.

[0053] The heavily doped InP contact layer 6 serves as both a selective etching stop layer and an N-type electrode contact layer for the InGaAs avalanche focal plane detector pixel. The InGaAs absorption layer 7 is adjacent to the heavily doped InP contact layer 6 to reduce the absorption of InP photons in the 400 nm–925 nm visible and near-infrared range and improve the incident light absorption efficiency. The charge layer 9 is InP, the avalanche layer 10 is InP, and the detector doping structure is P-on-N.

[0054] The following is a specific embodiment 1. The purpose of this embodiment is to realize an InGaAs avalanche focal plane detector with an integrated multi-spectral filter and a wide spectral response capability in the visible-near infrared range, using the avalanche detector material structure and manufacturing method of the present invention, specifically for an InGaAs avalanche focal plane detector employing an InP multiplication layer and a back-illuminated structure, thus verifying the feasibility of the present invention. The avalanche focal plane detector adopts a P-on-N doped structure, and its structural schematic diagram is shown in the attached diagram. Figure 5 From bottom to top, it includes: a semi-insulating InP substrate 3, 350 μm thick; an N-type InP etching sacrificial layer 4, which also serves as an epitaxial buffer layer, 2000 nm thick; and an N-type In... 0.53 Ga 0.47 As corrosion sacrificial layer 5, 500 nm thick; N-type heavily doped (N+) InP contact layer 6, 40 nm thick; unintentionally doped In 0.53 Ga 0.47 As absorption layer 7, thickness 2000 nm; unintentionally doped InGaAsP band transition layer a, thickness 20 nm; unintentionally doped InGaAsP band transition layer b, thickness 20 nm; unintentionally doped InGaAsP band transition layer c, thickness 20 nm; unintentionally doped InGaAsP band transition layer a, unintentionally doped InGaAsP band transition layer b and unintentionally doped InGaAsP band transition layer c together constitute band transition layer 8; N-type moderately doped InP charge layer 9, thickness 120 nm; unintentionally doped InP avalanche layer 10, thickness 3500 nm.

[0055] The fabrication steps for a multi-band InGaAs avalanche focal plane array detector are as follows:

[0056] Step 1: The InGaAs avalanche focal plane array and the Si readout circuit 13 are interconnected by flip soldering through indium pillars 12, and the gaps between the indium pillars 12 are filled with adhesive. After curing, the avalanche focal plane array module is formed.

[0057] Step 2: Fix the avalanche focal plane module onto a quartz carrier with paraffin wax, and use No. 303 corundum powder polishing slurry to mechanically rotate and grind one side of the InP substrate 3 on a grinding disk to thin it to 50 μm.

[0058] Step 3: Place the thinned and polished avalanche focal plane module into a selective etching solution with a volume ratio of HCl:H3PO4:H2O = 1:3:3 to remove the remaining InP substrate 3 and the InP etching sacrificial layer 4, and stop at the InGaAs etching sacrificial layer 5.

[0059] Step four: Place the avalanche focal plane module obtained in step three into a selective etching solution with a volume ratio of tartaric acid:H2O2:H2O = 1:5:5 to remove the InGaAs etching sacrificial layer 5 and stop at the heavily doped InP contact layer 6.

[0060] Step 5: After the corrosion is completed, the avalanche focal plane module is cleaned and dried, and then separated from the quartz carrier by heating.

[0061] Step 6: Using quartz as a transparent optical substrate, TiO2 and SiO2 dielectric films are alternately deposited on its surface using physical vapor deposition to form a lower high-reflectivity film; wherein TiO2 is used as a high-refractive-index dielectric film and SiO2 is used as a low-refractive-index dielectric film.

[0062] Step 7: Deposit a SiO2 resonant cavity layer on the surface of the lower high-reflectivity film, and adjust the thickness of the SiO2 resonant cavity layer in different regions through regional photolithography and physical vapor deposition processes, so that each region corresponds to a different central transmission wavelength.

[0063] Step 8: After completing the fabrication of the regional resonant cavity layer, TiO2 and SiO2 dielectric films are deposited alternately on its surface to form an upper high-reflectivity film. The upper and lower high-reflectivity films use the same number of film layer cycles, so that different regions form Fabry-Perot narrowband filter units with different central transmission wavelengths, thus obtaining a multi-spectral integrated filter 1.

[0064] Step nine: The SiO2 resonant cavity layer thicknesses in different Fabry-Perot narrowband filter units are set to 154 nm, 182 nm, 223 nm, 291 nm, 364 nm, 449 nm, 531 nm, and 582 nm, respectively, corresponding to center transmission wavelengths of 450 nm, 532 nm, 650 nm, 850 nm, 1064 nm, 1310 nm, 1550 nm, and 1700 nm. These resonant cavity layers of different thicknesses form eight Fabry-Perot narrowband filter units with different center transmission wavelengths, thus constituting a multispectral integrated filter 1.

[0065] Step 10: The multi-band integrated filter 1 is mounted on one side of the ultrathin heavily doped InP contact layer 6 of the broadband InGaAs avalanche focal plane module via a ceramic support 2, and each FP narrowband filter unit is aligned and adjusted to cover the corresponding pixel sub-array area; the ceramic support 2 defines the interval between the multi-band integrated filter 1 and the detector incident surface as 100 μm.

[0066] After the above process is completed, a multi-spectral InGaAs avalanche focal plane array detector is obtained, the structure of which is shown in the appendix. Figure 6 .

[0067] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. All equivalent changes and modifications made within the scope of the claims of this invention should be considered within the technical scope of this invention.

Claims

1. A multi-band InGaAs avalanche focal plane detector, characterized in that: It is composed of a multi-band integrated filter (1) and an InGaAs avalanche focal plane detector. The InGaAs avalanche focal plane detector includes a heavily doped InP contact layer (6), an InGaAs absorption layer (7), a band transition layer (8), a charge layer (9), an avalanche layer (10), a P-type electrode contact layer (11), an indium pillar (12), and a Si readout circuit (13). The multi-band integrated filter (1) is mounted on the heavily doped InP contact layer (6) through a ceramic support (2). The pixel array size of the InGaAs avalanche focal plane detector is M×N; correspondingly, the multi-band integrated filter (1) is a microstructure array filter composed of multiple filter units, each filter unit is divided sequentially along the column direction of the pixel array and covers the corresponding pixel subarray.

2. The multi-band InGaAs avalanche focal plane detector according to claim 1, characterized in that: The multi-band integrated filter (1) is composed of multiple Fabry-Perot narrowband filter units, each of which includes a lower high-reflectivity film, a resonant cavity layer, and an upper high-reflectivity film.

3. The multi-band InGaAs avalanche focal plane detector according to claim 2, characterized in that: The lower and upper high-reflectivity films are formed by alternating stacking of high-refractive-index dielectric films and low-refractive-index dielectric films. The high-refractive-index dielectric films are TiO2, Ta2O5, ZnS, or Si3N4, and the low-refractive-index dielectric films are SiO2, MgF2, or Al2O3. The resonant cavity layer is a transparent dielectric layer of SiO2, MgF2, Al2O3, Si3N4, Ta2O5, TiO2, or ZnS. The resonant cavity layers in different narrowband filter units have different optical thicknesses to achieve different center transmission wavelengths.

4. The multi-band InGaAs avalanche focal plane detector according to claim 3, characterized in that: The multi-band integrated filter (1) has 2 to 32 spectral channels, covering a spectral range of 400 to 1700 nm, and the filter bandwidth of each spectral channel is 10 to 100 nm.

5. The multi-band InGaAs avalanche focal plane detector according to claim 1, characterized in that: The thickness of the heavily doped InP contact layer (6) is 10–80 nm, the doping type is N, and the doping concentration is ≥1×10⁻⁶. 18 cm -3 The heavily doped InP contact layer (6) also serves as the N-type electrode contact layer for the InGaAs avalanche focal plane detector pixel; the InGaAs avalanche focal plane detector operates in Geiger mode and employs a photon counting working system.

6. The multi-band InGaAs avalanche focal plane detector according to claim 1, characterized in that: The height of the ceramic support (2) is 10-100 μm.

7. The multi-band InGaAs avalanche focal plane detector according to claim 1, characterized in that: The total number of filter units in the multi-band integrated filter (1) is Y, where the pixel area covered by the i-th filter is M× Let i = 1, 2, ..., Y, and satisfy... Furthermore, the coverage areas of all filter units are arranged sequentially in the column direction without overlapping, and satisfy the following conditions: This constitutes a multi-spectral filter integrated structure that completely covers the M×N pixel array.

8. A method for fabricating a multi-band InGaAs avalanche focal plane array detector according to any one of claims 1-7, characterized in that: Includes the following steps, S1, Prepare an InGaAs avalanche focal plane module interconnected with the Si readout circuit (13). The InGaAs avalanche focal plane module includes an InP substrate (3), an InP etched sacrificial layer (4), an InGaAs etched sacrificial layer (5), a heavily doped InP contact layer (6), an InGaAs absorption layer (7), a band transition layer (8), a charge layer (9), an avalanche layer (10), and a P-type electrode contact layer (11). The Si readout circuit (13) is interconnected with the InGaAs avalanche focal plane module through an indium pillar (12). S2, the InP substrate (3) is mechanically ground to thin it to a remaining thickness of 50 μm to 100 μm; then a two-step selective chemical etching process is used. First, the remaining InP substrate (3) and the InP etching sacrificial layer (4) are removed using an etching solution containing HCl:H3PO4, and the process stops at the InGaAs etching sacrificial layer (5); then, the InGaAs etching sacrificial layer (5) is removed using an etching solution containing tartaric acid:H2O2, and the process stops at the heavily doped InP contact layer (6) to obtain the InGaAs avalanche focal plane detector. S3, supported by a transparent optical substrate, a lower high-reflectivity film composed of alternating high and low refractive index dielectric films is deposited, and a resonant cavity layer is formed on the lower high-reflectivity film; S4, the thickness of the resonant cavity layer in different regions is controlled by regional photolithography and selective etching or step-by-step deposition process. Then, a high-reflection film composed of alternating high and low refractive index dielectric films is deposited, so that FP narrowband filter units with different central transmission wavelengths are formed in different regions, and multi-spectral integrated filter (1) is obtained. S5, the multi-band integrated filter (1) is installed on the heavily doped InP contact layer (6) on the incident surface side of the InGaAs avalanche focal plane detector through a ceramic bracket (2), and different narrowband filter units are set to correspond to the detector pixel area to achieve multi-band selective transmission and detection of incident light.

9. The method for fabricating a multi-band InGaAs avalanche focal plane array detector according to claim 8, characterized in that: The InP etch sacrificial layer (4) has a thickness of 5 nm to 10 μm, the InGaAs etch sacrificial layer (5) has a thickness of 5 nm to 5 μm, and the heavily doped InP contact layer (6) has a thickness of 10 nm to 100 nm.

10. The method for fabricating a multi-band InGaAs avalanche focal plane array detector according to claim 8, characterized in that: The heavily doped InP contact layer (6) serves as both a selective etching stop layer and an N-type electrode contact layer for the InGaAs avalanche focal plane detector pixel; the InGaAs absorption layer (7) is adjacent to the heavily doped InP contact layer (6) to reduce the absorption of InP 400 nm to 925 nm visible and near-infrared photons and improve the incident light absorption efficiency; the charge layer (9) is InP, the avalanche layer (10) is InP, and the detector doping structure is P-on-N.

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