Surface microstructured wide-spectrum detector and method of manufacture

Abstract

This application provides a broadband detector with enhanced surface microstructure and its fabrication method, relating to the field of photodetector technology. The broadband detector includes: an N-type doped contact layer; functional layers and a second detector electrode are respectively disposed in different regions of the lower surface of the N-type doped contact layer; the functional layer includes a barrier layer, an absorption layer, and a P-type doped contact layer stacked sequentially from top to bottom; a first detector electrode is disposed on the lower surface of the P-type doped contact layer, and a passivation layer disposed vertically on the side of the functional layer; a surface microstructure array is formed on the upper surface of the N-type doped contact layer, the surface microstructure array including multiple microstructure units arranged at intervals and periodically, and an antireflection layer is disposed on the exposed areas of the surface microstructure array and the upper surface of the N-type doped contact layer. The broadband detector of this application can excite lateral guided modes, improve the incident light angle tolerance, and enhance the absorption efficiency of multi-band light.

Description

Technical Field

[0001] This application relates to the field of photodetector technology, specifically to a broadband detector with enhanced surface microstructure and its fabrication method. Background Technology

[0002] Broadband detection technology covering the visible to mid-infrared band (0.4μm~5.0μm) is a core technology in aerospace remote sensing, security monitoring and other fields. At present, various fields have put forward higher application requirements for the wideband response capability, light absorption efficiency, working stability and integration of detectors.

[0003] Traditional broadband detectors often employ planar stacked structures, which have several technical drawbacks: First, planar structures are prone to specular reflection of light, and a single planar antireflection layer is difficult to adapt to multi-band optical characteristics, resulting in low light absorption efficiency. Some microstructure improvement schemes also suffer from limited material selection and parameters not optimized for broadband spectral performance, failing to simultaneously enhance light absorption across multiple sub-bands. Second, the lack of effective passivation protection on the functional layer sides easily leads to leakage current and increased dark current. The rational design of the gold-based electrodes has also not received sufficient attention, affecting the efficiency of electrical signal transmission. Third, the fabrication process has poor integration. Improper coordination between substrate removal, microstructure etching, and antireflection layer deposition processes can easily lead to microstructure morphology distortion, uneven antireflection layer thickness, poor dimensional consistency of the fabricated microstructure, and low device yield. Furthermore, current broadband imaging systems typically rely on the integration of multiple discrete single-spectral detectors, which requires complex image registration algorithms and correction of optical axis misalignment and resolution mismatch between subsystems. This results in complex system structures, heavy weight, and high costs. Therefore, developing optical structures that integrate multiple mechanisms for synergistic enhancement using a single detector still faces challenges. Summary of the Invention

[0004] In view of this, this application provides a broadband detector with enhanced surface microstructure and its fabrication method, which solves the problem that the spectral response range of existing photodetectors is limited due to a single absorption layer and reflection loss.

[0005] The first aspect of this application provides a broadband detector with enhanced surface microstructure, comprising: an N-type doped contact layer, wherein a functional layer and a second detector electrode are respectively disposed in different regions of the lower surface of the N-type doped contact layer; the functional layer comprises a barrier layer, an absorption layer and a P-type doped contact layer stacked sequentially from top to bottom; and a first detector electrode is disposed on the lower surface of the P-type doped contact layer, and a passivation layer disposed vertically on the side of the functional layer; a surface microstructure array is formed on the upper surface of the N-type doped contact layer, the surface microstructure array comprising a plurality of microstructure units arranged at intervals and periodically, and an antireflection layer is disposed on the exposed areas of the surface of the surface microstructure array and the upper surface of the N-type doped contact layer.

[0006] Furthermore, the broadband detector also includes a readout circuit; the readout circuit includes a readout circuit substrate and a first readout circuit electrode and a second readout circuit electrode respectively disposed on the upper surface of the readout circuit substrate; wherein, the first readout circuit electrode and the first detector electrode are connected through a first indium pillar; the second readout circuit electrode and the second detector electrode are connected through a second indium pillar.

[0007] Furthermore, the material of the absorption layer includes short-wave infrared material, mid-wave infrared material, long-wave infrared material, or very long-wave infrared material.

[0008] Furthermore, the material of the surface microstructure array includes at least one of indium antimony arsenide, gallium antimonide, gallium arsenide, indium arsenide, indium phosphide, germanium, and silicon;

[0009] Each microstructure unit has a cross-sectional shape that is rectangular, trapezoidal, inverted trapezoidal, or funnel-shaped.

[0010] Furthermore, the surface microstructure array can enhance the light absorption efficiency of multiple sub-bands of the broadband detector; the period of the surface microstructure array is 0.5 to 1.0 times the center wavelength of the sub-band, the depth is 100 nm to 2000 nm, and the duty cycle is 0.2 to 0.8.

[0011] Furthermore, the antireflective layer is made of at least one of silicon oxide, titanium oxide, zinc sulfide, magnesium fluoride, germanium, aluminum oxide, and tantalum oxide.

[0012] Furthermore, the passivation layer material includes at least one of silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, tantalum oxide, and zinc sulfide.

[0013] Furthermore, the materials of the first electrode and the second electrode of the detector are gold or gold-containing stacked structures, and the thickness of both the first electrode and the second electrode of the detector is greater than 100 nm.

[0014] The second aspect of this application provides a method for fabricating a broadband detector with enhanced surface microstructure, comprising: step S1, performing patterned etching on an epitaxial structure containing a substrate, an etch stop layer, an N-type doped contact layer, a barrier layer, an absorption layer, and a P-type doped contact layer stacked sequentially to form a mesa structure and expose a portion of the surface of the N-type doped contact layer; step S2, forming a first detector electrode on the surface of the P-type doped contact layer and a second detector electrode on the surface of the N-type doped contact layer; forming a first indium pillar on the first detector electrode and a second indium pillar on the second detector electrode; step S3, electrically connecting the first and second indium pillars to the electrodes of a readout circuit; step S4, removing the substrate and exposing the etch stop layer; and step S5, forming a surface microstructure array on the etch stop layer and covering the surface microstructure array and the surface of the N-type doped contact layer with an antireflection layer to obtain a broadband detector.

[0015] Furthermore, step S1 also includes: patterning the epitaxial structure using inductively coupled plasma etching or wet etching.

[0016] Furthermore, after forming the mesa structure, a passivation layer is applied to the side surface composed of the barrier layer, the absorption layer, and the P-type doped contact layer.

[0017] Further, substrate removal includes: thinning the substrate to 50μm~100μm using mechanical grinding and polishing; and removing the thinned substrate using a chemical etching solution to expose the etch stop layer.

[0018] Furthermore, forming a surface microstructure array on the etch stop layer includes: forming a microstructure mask on the etch stop layer; using the microstructure mask as a barrier layer to transfer the pattern to the etch stop layer, forming a surface microstructure array composed of periodically arranged microstructure units.

[0019] Further, forming an antireflection layer on the surface microstructure array includes: forming a protective region on the surface microstructure array; depositing an antireflection layer on the surface microstructure array and the protective region; removing the antireflection layer on the protective region and the surface, while retaining the antireflection layer on the surface microstructure array.

[0020] This application proposes a broadband detector with enhanced surface microstructure and its fabrication method, which has at least the following beneficial effects:

[0021] (1) Improve the tolerance of incident light angle: By exciting the transverse guided mode through the surface microstructure array, the tolerance of the detector to the incident light angle is significantly improved, so that the detector can maintain efficient light absorption capability in a wider range of incident angles.

[0022] (2) Achieving wide-spectrum detection capability: This detector can achieve wide-spectrum detection from visible light to mid-infrared, covering a wide spectral range from visible light to mid-infrared, solving the problem of narrow spectral response range of traditional detectors;

[0023] (3) Reduce leakage current and dark current: By covering the side of the functional layer with a passivation layer set in the vertical direction, the side of the functional layer is effectively protected, leakage current and dark current problems are reduced, and the efficiency of electrical signal transmission is improved.

[0024] (4) Improve device yield: By optimizing the fabrication process (the process coordination of substrate removal, microstructure etching and antireflection layer deposition), the size consistency of microstructure fabrication is improved, and problems such as poor connection of traditional fabrication processes, microstructure morphology distortion and uneven thickness of antireflection layer are solved, thereby improving device yield. Attached Figure Description

[0025] Figure 1A cross-sectional view of a surface microstructure-enhanced broadband detector according to an embodiment of this application is schematically shown;

[0026] Figure 2a The diagram schematically illustrates an array arrangement of circular surface microstructures according to an embodiment of this application;

[0027] Figure 2b The diagram schematically illustrates an array arrangement of square surface microstructures according to an embodiment of this application;

[0028] Figure 2c The diagram schematically illustrates an array arrangement of cross-shaped surface microstructures according to an embodiment of this application.

[0029] Figure 3 A flowchart illustrating a method for fabricating a surface microstructure-enhanced broadband detector according to an embodiment of this application is shown schematically.

[0030] Figure 4a A cross-sectional view following step S1 according to an embodiment of this application is shown schematically;

[0031] Figure 4b A cross-sectional view after step S4 according to an embodiment of this application is shown schematically;

[0032] Figure 4c A cross-sectional view following step S5 according to an embodiment of this application is shown schematically. Detailed Implementation

[0033] The embodiments of this application will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of this application. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of this application for ease of explanation. However, it will be apparent that one or more embodiments may be implemented without these specific details. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of this application.

[0034] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The terms “comprising,” “including,” etc., as used herein indicate the presence of features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0035] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0036] Figure 1 A cross-sectional view of a surface microstructure-enhanced broadband detector according to an embodiment of this application is schematically shown.

[0037] like Figure 1 As shown, the surface microstructure-enhanced broadband detector of this application embodiment includes: an N-type doped contact layer 12, with functional layers and detector second electrodes 18 respectively disposed in different regions of the lower surface of the N-type doped contact layer 12; the functional layer includes a barrier layer 13, an absorption layer 14 and a P-type doped contact layer 15 stacked sequentially from top to bottom; and a detector first electrode 17 is disposed on the lower surface of the P-type doped contact layer 15, and a passivation layer 16 disposed in a vertical direction is also covered on the side of the functional layer; a surface microstructure array 111 is formed on the upper surface of the N-type doped contact layer 12, the surface microstructure array 111 includes a plurality of microstructure units arranged at intervals and periodically, and the exposed areas of the surface of the surface microstructure array 111 and the upper surface of the N-type doped contact layer 12 are covered with an antireflection layer 4.

[0038] Through the above-mentioned composition structure, thus forming Figure 1 The detector absorption structure 1 of the broadband detector is used to achieve broadband and efficient light absorption.

[0039] In this embodiment, the broadband detector further includes a readout circuit 2; the readout circuit 2 includes a readout circuit substrate 21 and a first readout circuit electrode 22 and a second readout circuit electrode 23 respectively disposed on the upper surface of the readout circuit substrate 21; wherein, the first readout circuit electrode 22 and the first detector electrode 17 are connected through a first indium pillar 24; the second readout circuit electrode 23 and the second detector electrode 18 are connected through a second indium pillar 25.

[0040] The readout circuit substrate 21 is preferably made of silicon or gallium arsenide, with a thickness of 500 μm to 1000 μm, and its surface is precision polished to ensure a flatness of less than 0.1 μm. The first electrode 22 and the second electrode 23 of the readout circuit adopt a multilayer metal structure design, specifically including: a titanium layer (thickness 10 nm to 50 nm), a platinum layer (thickness 20 nm to 50 nm), and a gold layer (thickness 100 nm to 300 nm), i.e., a Ti / Pt / Au structure.

[0041] In this embodiment, a filler adhesive 26 is filled in the area between the detector absorption structure 1 and the readout circuit 2. The filler adhesive 26 can be made of at least one of epoxy resin, polyimide, benzocyclobutene or silicon-based polymer, which is used to effectively protect the internal structure and support the detector absorption structure 1.

[0042] In this embodiment, the material of the absorption layer 14 includes short-wave infrared material, mid-wave infrared material, long-wave infrared material, or very long-wave infrared material.

[0043] Specifically, the material of the absorption layer 14 can be selected from short-wave infrared (SWIR, wavelength range 1μm-2.5μm), mid-wave infrared (MWIR, wavelength range 3μm-5μm), long-wave infrared (LWIR, wavelength range 8μm-12μm), or very long-wave infrared (VLWIR, wavelength range 12μm-20μm) materials and combinations thereof. For example, InAs / GaSb superlattice (thickness 2μm-4μm). Through bandgap engineering design, the InAs / GaSb superlattice material enables the absorption layer to maintain high light absorption efficiency in the visible to mid-wave infrared band (0.4μm-5μm), covering a wide spectral range without the need for a multi-layer stacked structure.

[0044] The material of the absorption layer 14 can achieve a continuous response from visible light (0.4μm) to mid-wave infrared (5μm), solving the problem of traditional detectors requiring multi-chip integration and enabling the detector to complete broadband imaging in a single device; at the same time, the band structure of the InAs / GaSb superlattice and the surface microstructure work together to improve the light absorption efficiency by more than 60% (compared to 30% improvement compared to the planar structure), significantly improving the signal-to-noise ratio.

[0045] In this embodiment, the surface microstructure array 111 can enhance the light absorption efficiency of multiple sub-bands of the broadband detector; the period of the surface microstructure array 111 is 0.5 to 1.0 times the center wavelength of the sub-band, the depth is 100 nm to 2000 nm, and the duty cycle is 0.2 to 0.8.

[0046] For example, the parameter design of the surface microstructure array 111 is based on the synergistic effect of guided mode resonance (GMR) and Fabry-Perot (FP) optical resonance, and its parameter range is determined through optical simulation and experimental optimization.

[0047] Specifically, the period of the microstructure unit is the distance between the centers of two adjacent microstructure units, that is, the period is 0.5 to 1.0 times the center wavelength of the sub-band (for example, for the 1.0 μm band, the period is 0.5 μm to 1.0 μm), to ensure multi-band resonance in a wide spectral range from visible light (0.4 μm to 0.7 μm) to MWIR (3 μm to 5 μm); the depth of the microstructure unit is the vertical height of the microstructure unit from the surface to the bottom. The depth affects the propagation path length of light in the microstructure, and the depth value is 100 nm to 2000 nm, to achieve continuous spectral coverage from visible light to MWIR, eliminating the band limitations of traditional single microstructure units; the duty cycle of the microstructure unit is the ratio of the width of the microstructure unit to the period, and the duty cycle value is 0.2 to 0.8, which can balance optical coupling and mechanical strength, improve light absorption efficiency while ensuring the feasibility of microstructure fabrication.

[0048] In this embodiment, the antireflection layer 4 is made of at least one of silicon oxide, titanium oxide, zinc sulfide, magnesium fluoride, germanium, aluminum oxide, and tantalum oxide.

[0049] The aforementioned material is formed by physical vapor deposition (such as electron beam evaporation), and its optical thickness is designed to match the center wavelength of the target enhancement band, so that the surface reflectivity of the detector in the visible light (0.4μm~0.7μm), short-wave infrared (1.0μm~2.5μm) and mid-wave infrared (3.0μm~5.0μm) bands is less than 5%, which significantly improves the light absorption efficiency.

[0050] In this embodiment, the material of the passivation layer 16 includes at least one of silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, tantalum oxide, and zinc sulfide.

[0051] Specifically, the passivation layer 16 covers all sidewalls of the functional layers (including the barrier layer 13, the absorption layer 14, and the p-type doped contact layer 15) and is formed using plasma-enhanced chemical vapor deposition (PECVD). Since conventional infrared detectors suffer from high dark current due to sidewall leakage (affecting nighttime imaging), the passivation layer 16 effectively blocks the sidewall leakage path, reducing the detector's dark current density to 10 at an operating temperature of 150K~200K. -4 A / cm 2 The following significantly improves the signal-to-noise ratio without requiring additional circuit compensation.

[0052] In this embodiment, the materials of the detector first electrode 17 and the detector second electrode 18 are gold or gold-containing stacked structures, and the thickness of the detector first electrode 17 and the detector second electrode 18 is greater than 100 nm.

[0053] Specifically, the first electrode 17 and the second electrode 18 of the detector adopt a gold or gold-containing stacked structure (such as Ti / Pt / Au), wherein the gold layer thickness is greater than 100 nm.

[0054] For example, by using a titanium layer to enhance the adhesion between the electrode and the detector, and a platinum layer to block gold diffusion, the contact resistance is reduced to below 50mΩ, while avoiding electrode oxidation and breakage, thus significantly improving the reliability and signal quality of the detector.

[0055] In this embodiment, incident light enters from one side of the antireflection layer 4 and the surface microstructure array 111, and after being modulated by the surface microstructure array and interacting with the antireflection layer, it enters the detector absorption structure 1. The absorption layer 14 absorbs photons and generates photogenerated carriers. Under an applied bias voltage, photogenerated holes move towards the P-type doped contact layer 15 and are output to the readout circuit 2 through the detector's first electrode 17 and the first indium pillar 24; photogenerated electrons move towards the N-type doped contact layer 12 and are output to the readout circuit 2 through the detector's second electrode 18 and the second indium pillar 25. The directional movement of photogenerated carriers forms a photocurrent, and by reading this current signal, the detection of broadband light is achieved.

[0056] Furthermore, the surface microstructure array 111 significantly enhances the localization and optical path length of light within the absorption layer by exciting guided mode resonance and forming a Fabry-Perot resonance with the bottom reflective structure; the antireflection layer effectively reduces surface reflection loss. The synergistic effect of these two elements greatly improves the photon injection and absorption efficiency of the detector in the visible to mid-infrared band, thereby enhancing the device's broadband quantum efficiency.

[0057] Figure 2a The diagram schematically illustrates an array arrangement of circular surface microstructures according to an embodiment of this application; Figure 2b The diagram schematically illustrates an array arrangement of square surface microstructures according to an embodiment of this application; Figure 2c An array arrangement diagram of cross-shaped surface microstructures according to an embodiment of this application is shown schematically.

[0058] In this embodiment, the material of the surface microstructure array 111 includes at least one of indium antimony arsenide, gallium antimonide, gallium arsenide, indium arsenide, indium phosphide, germanium, and silicon; wherein, the cross-sectional shape of each microstructure unit is rectangular, trapezoidal, inverted trapezoidal, or funnel-shaped, and the top view shape of each microstructure unit is circular, square, or cross-shaped.

[0059] like Figure 2a The diagram shows an array of circular surface microstructures, where each microstructure unit has a circular top view and is uniformly distributed across the detector surface. These circular microstructures can be arranged in a tetragonal close-packed or hexagonal close-packed configuration to ensure uniformity of response across the entire photosensitive surface.

[0060] Among them, the four-sided close-packed arrangement consists of four adjacent circular microstructures surrounding each other, forming a regular square grid; the six-sided close-packed arrangement consists of six adjacent circular microstructures surrounding each other, forming a honeycomb pattern. This arrangement maximizes the fill rate and reduces voids. Both the four-sided and six-sided close-packed arrangements can effectively improve optical coupling efficiency and reduce reflection loss. Furthermore, due to their symmetry, circular microstructures exhibit consistent optical properties in all directions, making them suitable for applications requiring uniform light absorption.

[0061] like Figure 2b The diagram shows an array of square surface microstructures. Each microstructure unit has a square top view and is neatly arranged on the detector surface. Square microstructures are typically arranged in a close-packed manner, meaning that each square microstructure is surrounded by four adjacent square microstructures, forming a regular matrix layout.

[0062] Square microstructures facilitate alignment and etching in the manufacturing process, making them particularly suitable for large-scale production. The regular matrix layout helps simplify subsequent process steps, such as antireflection layer deposition and electrode fabrication. At the same time, square microstructures have smaller edge effects, which is beneficial for improving overall light absorption efficiency.

[0063] like Figure 2c The diagram shows an array of cross-shaped surface microstructures. Each microstructure unit has a cross-shaped top view and is distributed on the detector surface. The cross-shaped microstructures can be arranged in a close-packed manner to form a regular matrix layout.

[0064] The cross-shaped microstructure has a unique geometry that can enhance the optical coupling effect in a specific direction, making it particularly suitable for applications that require directional light absorption. While maintaining a high fill rate, it provides more edge interfaces, increases photon scattering paths, and thus improves light absorption efficiency. At the same time, this structure can also effectively suppress sidewall leakage current and improve the overall performance of the device.

[0065] Figure 3 A flowchart illustrating a method for fabricating a surface microstructure-enhanced broadband detector according to an embodiment of this application is shown schematically. Figure 4a A cross-sectional view following step S1 according to an embodiment of this application is shown schematically; Figure 4b A cross-sectional view after step S4 according to an embodiment of this application is shown schematically; Figure 4c A cross-sectional view following step S5 according to an embodiment of this application is shown schematically.

[0066] like Figure 3 The method for fabricating a broadband detector with enhanced surface microstructure, as shown, includes:

[0067] Step S1 involves patterning etching on an epitaxial structure containing a substrate 3, an etch stop layer 11, an N-type doped contact layer 12, a barrier layer 13, an absorber layer 14, and a P-type doped contact layer 15 stacked sequentially to form a mesa structure and expose part of the surface of the N-type doped contact layer 12.

[0068] In this embodiment, a stop layer 11, an N-type doped contact layer 12, a barrier layer 13, an absorber layer 14, and a P-type doped contact layer 15 are sequentially etched on one side of the substrate 3 using molecular beam epitaxy to form an epitaxial structure in preparation for subsequent etching.

[0069] In this embodiment, step S1 further includes: patterning the epitaxial structure using inductively coupled plasma etching or wet etching.

[0070] For example, patterned etching can be performed using inductively coupled plasma dry etching, chemical solution wet etching, or a combination of inductively coupled plasma dry etching and chemical solution wet etching. The etching depth can be just enough to expose the N-type doped contact layer 12 to half its thickness.

[0071] Optionally, the gas used in inductively coupled plasma dry etching can be a mixture of chlorine (Cl2), boron trichloride (BCl3), and argon (Ar). Optionally, the chemical solution can be a solution of citric acid: phosphoric acid: hydrogen peroxide: water in a ratio of 1:1:2:20.

[0072] In this embodiment, after forming the mesa structure, a passivation layer 16 is covered on the side surface composed of the barrier layer 13, the absorption layer 14, and the p-type doped contact layer 15, as shown below. Figure 4a The cross-sectional view shown.

[0073] The passivation layer 16 can be formed by plasma-enhanced chemical vapor deposition, electron beam, thermal evaporation or atomic layer deposition.

[0074] Step S2: A detector first electrode 17 is formed on the surface of the P-type doped contact layer, and a detector second electrode 18 is formed on the surface of the N-type doped contact layer 12; a first indium pillar 24 is formed on the detector first electrode 17, and a second indium pillar 25 is formed on the detector second electrode 18.

[0075] In this embodiment, the electrodes and indium pillars of the detector and readout circuit can be fabricated using a negative adhesive stripping process.

[0076] Step S3, an electrical connection is made with the electrodes of the readout circuit 2 through the first indium pillar 24 and the second indium pillar 25.

[0077] In this embodiment, the detector absorption structure 1 and the readout circuit 2 are interconnected by indium pillar flip-chip bonding. The indium pillar flip-chip bonding process is carried out by high-precision flip-chip bonding equipment. After optical alignment of the detector and the readout circuit, the corresponding indium pillars are thermo-bonded under certain temperature and pressure to form an interconnection structure, namely the first indium pillar 24 and the second indium pillar 25.

[0078] Step S4, remove substrate 3 and expose etch stop layer 11, as shown. Figure 4b The cross-sectional view shown.

[0079] In this embodiment, removing the substrate 3 includes: thinning the substrate 3 to 50μm~100μm by mechanical grinding and polishing; and removing the thinned substrate 3 by chemical etching solution to expose the etch stop layer 11.

[0080] Alternatively, the chemical etching solution may be a chromium trioxide (CrO3):hydrogen fluoride (HF):water (H2O) solution with a ratio of 10:1:20, to selectively etch the detector substrate 3 without etching the etching stop layer 11.

[0081] Step S5: A surface microstructure array 111 is formed on the etch stop layer 11, and an antireflection layer 4 is coated on the surface of the surface microstructure array 111 and the N-type doped contact layer 12, thereby obtaining a broadband detector, such as... Figure 4c The cross-sectional view shown.

[0082] In this embodiment, forming a surface microstructure array 111 on the etch stop layer 11 includes: forming a microstructure mask on the etch stop layer 11; using the microstructure mask as a barrier layer, transferring the pattern to the etch stop layer 11 to form a surface microstructure array 111 composed of periodically arranged microstructure units.

[0083] The surface microstructure array 111 can be formed by directly etching the etch stop layer 11. Specifically, a patterned mask corresponding to the surface microstructure array is formed on the exposed surface of the etch stop layer 11. Subsequently, using the patterned mask as a barrier layer, inductively coupled plasma etching or wet etching is employed to etch the maskless region of the etch stop layer 11, transferring the pattern of the patterned mask into the etch stop layer 11. Optionally, the etching depth is controlled between 100 nm and 2000 nm. Finally, the remaining patterned mask is removed to obtain the surface microstructure array 111.

[0084] Optionally, a patterned dielectric layer can be deposited to form the surface microstructure array 111. Specifically, the etch stop layer 11 is first removed to expose the underlying N-type doped contact layer 12. Then, a dielectric layer of a different material than the N-type doped contact layer 12 is deposited on the surface of the N-type doped contact layer 12. Next, a patterned mask corresponding to the surface microstructure array is formed on the dielectric layer, and the dielectric layer is etched using the patterned mask as a barrier layer to form the surface microstructure array 111. Finally, any remaining patterned mask is removed.

[0085] In this embodiment, forming an antireflection layer on the surface microstructure array includes: forming a protective region on the surface microstructure array 111; depositing an antireflection layer 4 on the surface microstructure array 111 and the protective region; removing the antireflection layer 4 from the protective region and the surface, while retaining the antireflection layer 4 on the surface microstructure array 111.

[0086] For example, the antireflection layer 4 is prepared by physical vapor deposition, and its material is selected from at least one or a combination of silicon oxide, titanium oxide, zinc sulfide, magnesium fluoride, germanium, aluminum oxide, and tantalum oxide. Optionally, the optical thickness of the antireflection layer 4 is designed to be correlated with the center wavelength of the target enhancement response band in order to minimize reflectivity over a wide spectral range.

[0087] It should be noted that the above embodiments describe a mesa-type superlattice infrared detector and its fabrication method. The embodiments of this application can also be extended to mercury cadmium telluride, quantum well, or quantum dot detectors. Accordingly, the materials of the etching stop layer and the microstructure array can be adapted and selected according to the chosen absorption layer material system.

[0088] Those skilled in the art will understand that the features described in the various embodiments of this application can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in this application. In particular, the features described in the various embodiments of this application can be combined and / or combined in various ways without departing from the spirit and teachings of this application. All such combinations and / or combinations fall within the scope of this application.

[0089] The embodiments of this application have been described above. However, these embodiments are merely illustrative and not intended to limit the scope of this application. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. Without departing from the scope of this application, those skilled in the art can make various substitutions and modifications, all of which should fall within the scope of this application.

Claims

1. A broadband detector with enhanced surface microstructure, characterized in that, include: An N-type doped contact layer (12) is provided with functional layers and detector second electrodes (18) in different regions on the lower surface of the N-type doped contact layer (12); the functional layer includes a barrier layer (13), an absorption layer (14) and a P-type doped contact layer (15) stacked from top to bottom; and a detector first electrode (17) is provided on the lower surface of the P-type doped contact layer (15); and a passivation layer (16) is also provided on the side of the functional layer along the vertical direction. A surface microstructure array (111) is formed on the upper surface of the N-type doped contact layer (12). The surface microstructure array (111) includes a plurality of microstructure units that are spaced apart and arranged periodically. The exposed areas of the surface microstructure array (111) and the upper surface of the N-type doped contact layer (12) are covered with an anti-reflection layer (4).

2. The broadband detector according to claim 1, characterized in that, The broadband detector also includes a readout circuit (2); The readout circuit (2) includes a readout circuit substrate (21) and a first readout circuit electrode (22) and a second readout circuit electrode (23) respectively disposed on the upper surface of the readout circuit substrate (21); The first electrode (22) of the readout circuit and the first electrode (17) of the detector are connected by a first indium pillar (24); the second electrode (23) of the readout circuit and the second electrode (18) of the detector are connected by a second indium pillar (25).

3. The broadband detector according to claim 1, characterized in that, The material of the absorption layer (14) includes short-wave infrared material, mid-wave infrared material, long-wave infrared material or very long-wave infrared material.

4. The broadband detector according to claim 1, characterized in that, The material of the surface microstructure array (111) includes at least one of indium antimony arsenide, gallium antimonide, gallium arsenide, indium arsenide, indium phosphide, germanium, and silicon; The cross-sectional shape of each microstructure unit is rectangular, trapezoidal, inverted trapezoidal, or funnel-shaped.

5. The broadband detector according to claim 1, characterized in that, The surface microstructure array (111) can enhance the light absorption efficiency of multiple sub-bands of the broadband detector; The period of the surface microstructure array (111) is 0.5 to 1.0 times the center wavelength of the sub-band, the depth is 100 nm to 2000 nm, and the duty cycle is 0.2 to 0.

8.

6. The broadband detector according to claim 1, characterized in that, The antireflective layer (4) is made of at least one of silicon oxide, titanium oxide, zinc sulfide, magnesium fluoride, germanium, aluminum oxide and tantalum oxide.

7. The broadband detector according to claim 1, characterized in that, The material of the passivation layer (16) includes at least one of silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, tantalum oxide and zinc sulfide.

8. The broadband detector according to claim 1, characterized in that, The materials of the first electrode (17) and the second electrode (18) of the detector are gold or gold-containing stacked structures, and the thickness of the first electrode (17) and the second electrode (18) of the detector is greater than 100 nm.

9. A method for fabricating a broadband detector with enhanced surface microstructure, characterized in that, include: Step S1: Patterned etching is performed on the epitaxial structure containing a substrate (3), an etch stop layer (11), an N-type doped contact layer (12), a barrier layer (13), an absorption layer (14), and a P-type doped contact layer (15) stacked in sequence to form a mesa structure and expose part of the surface of the N-type doped contact layer (12). Step S2: A first detector electrode is formed on the surface of the P-type doped contact layer, and a second detector electrode is formed on the surface of the N-type doped contact layer; a first indium pillar (24) is formed on the first detector electrode, and a second indium pillar (25) is formed on the second detector electrode. Step S3, an electrical connection is made between the first indium pillar (24) and the second indium pillar (25) and the electrodes of the readout circuit 2; Step S4, remove the substrate (3) and expose the etch stop layer (11). Step S5: A surface microstructure array (111) is formed on the etch stop layer (11), and an antireflection layer (4) is covered on the surface microstructure array (111) and the N-type doped contact layer (12) to obtain the broadband detector.

10. The preparation method according to claim 9, characterized in that, Step S1 further includes: The epitaxial structure is patterned by inductively coupled plasma etching or wet etching.

11. The preparation method according to claim 9, characterized in that, After the mesa structure is formed, a passivation layer (16) is covered on the side composed of the barrier layer (13), the absorption layer (14) and the P-type doped contact layer (15).

12. The preparation method according to claim 9, characterized in that, Removing the substrate (3) includes: The substrate (3) was thinned to 50 μm to 100 μm by mechanical grinding and polishing; The thinned substrate (3) is removed using a chemical etching solution to expose the etching stop layer (11).

13. The preparation method according to claim 9, characterized in that, A surface microstructure array (111) is formed on the etch stop layer (11), including: A microstructure mask is formed on the etch stop layer (11); Using the microstructure mask as a barrier layer, the pattern is transferred to the etching stop layer (11) to form a surface microstructure array (111) composed of periodically arranged microstructure units.

14. The preparation method according to claim 9, characterized in that, The formation of the antireflection layer on the surface microstructure array includes: A protective region is formed on the surface microstructure array (111); An antireflection layer (4) is deposited on the surface microstructure array (111) and the protective region. Remove the antireflection layer (4) from the protected area and surface, and retain the antireflection layer (4) on the surface microstructure array (111).

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