A broadband microcavity array coupling structure for quantum well detectors and a method of manufacturing the same

Abstract

The application provides a broadband microcavity array coupling structure for a quantum well detector and a preparation method thereof. In the coupling structure, a plurality of microcavity units are arranged in an array, and the sizes of the plurality of microcavity units gradually change. Each microcavity unit supports electromagnetic waves of different frequency bands, so that the coupling frequency band can be effectively widened, the light absorption efficiency of the quantum well is improved, the dark current of the device is reduced, and the working temperature of the device is improved. In addition, the application adopts a standard GaAs material system process, which is simple and easy to operate, and does not increase the process difficulty of device preparation.

Description

Technical Field

[0001] This invention relates to the field of semiconductor photonic detectors, and more specifically to a broadband microcavity array coupling structure for quantum well detectors and its fabrication method. Background Technology

[0002] Terahertz (THz) waves typically refer to electromagnetic waves with frequencies ranging from 100 GHz to 10 THz, corresponding to wavelengths between 3 mm and 30 μm, falling between millimeter waves and infrared light. THz waves occupy a unique position in the electromagnetic spectrum, situated in the transition region from electronics to photonics. Their long-wavelength end overlaps with submillimeter waves, while their short-wavelength end overlaps with the far-infrared band. THz wave technology has vast application potential in information and communication technologies, biomedicine, space exploration, and global environmental monitoring.

[0003] Terahertz quantum well photodetectors (THz QWPs) based on inter-subband transitions possess high detection sensitivity and fast response capabilities. They also offer advantages such as a wide linear response range, simple design, mature material growth and device fabrication processes, and the ability to fabricate large-scale imaging arrays, making them ideal devices for space heterodyne detection, high-speed communication, and large-scale focal plane imaging. For example... Figure 1 As shown, the commonly used THz QWPs structure in the prior art includes: a GaAs substrate 1, a lower contact layer 8, an active region 4 and an upper contact layer 7 disposed sequentially from bottom to top on the upper surface of the GaAs substrate 1, a lower electrode 11 disposed on the upper surface of the GaAs substrate 1 and located on both sides of the lower contact layer 8, and an upper electrode 12 disposed on the upper surface of the upper contact layer 7. The active region 4 is composed of a GaAs / AlxGa1-xAs multi-quantum-well periodic structure. After the bound electrons in the quantum well absorb THz photons, they transition to the continuous state and form a photocurrent under an applied bias voltage. The THz wave is detected by measuring and analyzing the changes in the photocurrent.

[0004] Therefore, low inter-subband absorption efficiency is a key factor limiting the performance of THz QWPs, and improving the optical coupling method is crucial for achieving better THz QWPs performance. Currently, the two commonly used coupling methods for THz QWPs are: 45° beveled polished substrate coupling and metal scattering grating coupling. However, the 45° beveled polished substrate coupling mechanism cannot achieve normal light incidence (e.g., ...). Figure 1As shown, GaAs substrate 1 requires 45° bevel polishing (the incident light needs to enter from this 45° bevel), which is also detrimental to device integration. Although grating coupling can achieve normal incident light coupling, it does not significantly improve device performance. Subwavelength patch antenna coupling is a novel coupling method for THz QWPs. This coupling method is beneficial for large-scale integration and can significantly improve device performance. Currently, subwavelength patch antenna THz QWPs structures are all single-frequency operating and have not been applied to broadband THz QWPs.

[0005] In summary, the study of broadband subwavelength fractal patch antenna microcavity coupling units for broadband THz QWPs is of great significance. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, this invention provides a broadband microcavity array coupling structure for quantum well detectors and its fabrication method. In this coupling structure, multiple microcavity units are arranged in an array, and the size of the multiple microcavity units gradually varies. Each microcavity unit supports electromagnetic waves of different frequency bands, thereby effectively broadening the coupling frequency band, improving the light absorption efficiency of the quantum well, reducing the dark current of the device, and increasing the operating temperature of the device. In addition, this invention uses a standard GaAs material system process, which is simple and easy to operate, and does not add additional process difficulty to the device fabrication.

[0007] To achieve the above and other related objectives, the present invention provides a broadband microcavity array coupling structure for a quantum well detector, comprising: a substrate, and a plurality of microcavity units arranged in a uniform array above the substrate.

[0008] The plurality of microcavity units have N columns in a first direction and M rows in a second direction perpendicular to the first direction, where N≥1, M≥1, and the first side length of the microcavity unit in the first direction is L. i In the arrangement direction of the microcavity units, the first side length L of the plurality of microcavity units i Gradually increase;

[0009] The microcavity unit has a groove extending from the edge of the microcavity unit toward the center. The groove includes a first groove extending along the first direction and a second groove extending along the second direction. The first groove is symmetrically distributed along the central axis of symmetry of the microcavity unit in the second direction, and the second groove is symmetrically distributed along the central axis of symmetry of the microcavity unit in the first direction. The first groove and the second groove make the middle region of the microcavity unit a continuous region.

[0010] Optionally, in the first direction, the first side length L of the plurality of microcavity units i Satisfy Li -L i-1 =1μm, 2≤i≤N.

[0011] Optionally, along the second direction, the width of the first groove is W′. j , W′ j -W′ j-1 =2μm, 2≤j≤M.

[0012] Optionally, in the first direction, the first depth of the first groove is de', the first span distance of the continuous region in the first direction is d, and d = L i -2*de', the first depth de' of the plurality of microcavity units gradually increases in the arrangement direction of the microcavity units.

[0013] Optionally, the first span distance d is a fixed value.

[0014] Optionally, each of the microcavity units includes: an epitaxial layer, and an upper metal electrode disposed on the surface of the epitaxial layer, wherein the geometric dimensions of the epitaxial layer are the same as the geometric dimensions of the upper metal electrode;

[0015] All of the aforementioned microcavity units further include: a common lower metal electrode plate on which the epitaxial layer is disposed, the lower metal electrode plate being disposed on the surface of the substrate.

[0016] Optionally, the upper metal electrode is a subwavelength fractal patch antenna.

[0017] Optionally, in the second direction, the plurality of microcavity units are connected in series via microcavity connecting lines.

[0018] Optionally, a passivation layer is further provided on the surface of the lower metal electrode plate. The passivation layer fills the spaces between the plurality of microcavity units and the grooves, and the thickness of the passivation layer is equal to the thickness of the epitaxial layer.

[0019] Optionally, a metal layer is also provided on the back side of the substrate.

[0020] The present invention also provides a method for fabricating a broadband microcavity array coupling structure for a quantum well detector, comprising the following steps:

[0021] S1: Provide a sample material layer, which includes a first substrate and an epitaxial layer from bottom to top;

[0022] S2: Provide a second substrate, form a first metal material layer on the surface of the epitaxial layer of the sample material layer, and form a second metal material layer on the surface of the second substrate;

[0023] S3: Press and bond the first metal material layer and the second metal material layer to form the lower metal electrode plate;

[0024] S4: Remove the first substrate to expose the epitaxial layer, and form an upper metal electrode on the surface of the epitaxial layer;

[0025] S5: Etch the upper metal electrode and the epitaxial layer to form a plurality of microcavity units in the coupling structure, wherein the microcavity unit is any of the microcavity units described in the above-described technical solutions;

[0026] S6: A passivation layer is formed by filling the spaces between the multiple microcavity units and in the grooves of the microcavity units, and a microcavity connection line is deposited on the surface of the passivation layer to connect the multiple microcavity units to an external power source.

[0027] Optionally, after step S6, the second substrate may be thinned and a back gold layer may be formed on the side of the second substrate away from the lower metal electrode plate.

[0028] The broadband microcavity array coupling structure for quantum well detectors and its fabrication method provided by this invention have at least the following technical advantages:

[0029] 1. The upper metal electrode in the microcavity unit adopts a fractal patch antenna, which can effectively increase the effective absorption area of ​​the detector's photosensitive surface and improve the device's absorption efficiency of incident light.

[0030] 2. The microcavity unit with a double-sided metal structure can achieve resonance enhancement between the plasma wave inside the microcavity and the THz optical field, thereby improving the responsivity of the quantum well detector;

[0031] 3. The array structure composed of multiple microcavity units has a grating-like effect, which can change the direction of normally incident THz light to conform to the transition selection rule, so that it can be absorbed by the active region of the quantum well detector.

[0032] 4. The array has multiple microcavity units of varying sizes, which enables each microcavity unit to support electromagnetic waves of different frequency bands. This achieves resonance enhancement between plasma waves and incident light field within a certain frequency range. Furthermore, the superposition of electromagnetic waves of different frequency bands combined with the active region of broadband detection enables broadband detection.

[0033] 5. The subwavelength fractal patch antenna microcavity array coupling structure of the present invention is not only applicable to the THz band, but also to quantum well detectors in the infrared band, and has broad application prospects in the field of large-scale focal plane array imaging in the infrared and THz bands.

[0034] 6. The present invention has a high degree of design freedom. Designers can design the geometric dimensions of the microcavity unit according to the intrinsic frequency of the detector, so that the microcavity unit supports electromagnetic waves of a specific oscillation frequency, thereby achieving resonance enhancement between plasma waves and incident light field. Attached Figure Description

[0035] Figure 1 The diagram shows a structural schematic of mid-infrared and THz QWPs commonly used in the prior art.

[0036] Figure 2 The diagram shown is a schematic diagram of the broadband microcavity array coupling structure for a quantum well detector provided in Embodiment 1.

[0037] Figure 3 The image shown is a top view of the microcavity unit in Embodiment 1.

[0038] Figure 4 The image shown is a cross-sectional view of the microcavity unit in Example 1.

[0039] Figure 5 This is a schematic diagram showing the formation of a first metallic material layer on the surface of a sample material layer in Example 2.

[0040] Figure 6 This is a schematic diagram showing the formation of a second metal material layer on the surface of a second substrate in Embodiment 2.

[0041] Figure 7 The diagram shows the structure formed in step S3 of Example 2.

[0042] Figure 8 The diagram shows the structure formed in step S4 of Example 2.

[0043] Component designation explanation

[0044] 1. Electrode on substrate 12

[0045] 2. Lower metal electrode plate 100 microcavity unit

[0046] 3. Passivation layer 101 First groove

[0047] 4. Active area 102, second groove

[0048] 5. Continuous region of upper metal electrode 103

[0049] 6 Microcavity interconnects 110 First substrate

[0050] 7 Upper contact layer 111 Etching barrier layer

[0051] 8 Lower contact layer 112 First metallic material layer

[0052] 9. Back gold layer 210 Second substrate

[0053] 10 Epitaxial layer 211 Second metallic material layer

[0054] 11 Lower electrode Detailed Implementation

[0055] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0056] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Although the illustrations only show components related to the present invention and are not drawn according to the actual number, shape and size of the components, the shape, quantity, positional relationship and proportion of each component can be arbitrarily changed under the premise of realizing the technical solution of this invention, and the layout of the components may also be more complex.

[0057] Example 1

[0058] This embodiment provides a broadband microcavity array coupling structure for quantum well detectors, such as... Figure 2 As shown, it includes a substrate 1 and a plurality of microcavity units 100 arranged in a uniform array above the substrate 1.

[0059] like Figure 2 As shown, multiple microcavity units 100 have N columns in a first direction (i.e., the X direction shown in the figure) and M rows in a second direction perpendicular to the first direction (i.e., the Y direction shown in the figure), where N ≥ 1 and M ≥ 1. Figure 3 As shown, the first side length of the microcavity unit 100 in the first direction (i.e., the X direction shown in the figure) is L. i And along the first direction (i.e., the X direction shown in the figure), the first side length L of the plurality of microcavity units 100 i Gradually increase, satisfying L i -L i-1 = 1μm, 2≤i≤N. In this embodiment, the first side length L of the microcavity unit 100 is... i The minimum value is 21 μm. Multiple microcavity units are arranged in an array, which has a grating-like effect. It can change the direction of normally incident THz light to conform to the transition selection rule, so that it can be absorbed by the active region of the device.

[0060] like Figure 3As shown, the microcavity unit 100 has grooves extending from its edge to the center, including a first groove 101 extending along a first direction (i.e., the X direction shown in the figure) and a second groove 102 extending along a second direction (i.e., the Y direction shown in the figure). The first groove 101 is symmetrically distributed along the central axis of symmetry of the microcavity unit 100 in the second direction, and the second groove 102 is symmetrically distributed along the central axis of symmetry of the microcavity unit 100 in the first direction. The first groove 101 and the second groove 102 make the middle region of the microcavity unit 100 a continuous region 103.

[0061] like Figure 3 As shown, in the first direction (i.e., the X direction shown in the figure), the first depth of the first groove 101 is de', the first span distance of the continuous region 103 in the first direction is d, and the first depth de' of the multiple microcavity units 100 gradually increases along the first direction, satisfying d = L. i -2*de', and the first span distance d is a fixed value, for example, in this embodiment the first span distance d is 8μm; in the second direction (i.e. the Y direction shown in the figure), the width W′ of the first groove 101 of the plurality of microcavity units 100 is... j Gradually increase, satisfying W′ j -W′ j-1 = 2μm, 2≤j≤M, in this embodiment, the width W′ of the first groove 101 is 2μm. j The minimum value is 4 μm. The depth de” of the second groove 102 in the second direction (i.e., the Y direction shown in the figure) and the width W″ in the first direction are... j (i.e., the Y direction shown in the figure) is a fixed value. In this embodiment, the width W″ of the second groove 102 is... j The length is 4 μm. After determining the intrinsic probe frequency of the THz QWPs material, the aforementioned geometric dimensions of the microcavity unit 100 can be designed so that the microcavity unit supports electromagnetic wave modes equal to the intrinsic probe frequency of the THz QWPs; and by adjusting the first side length L of each microcavity unit 100 in the array... i The first depth de′ and width W′ of the first groove 101 j The gradient design of three parameters enables the gradual change of the operating frequency band of microcavity units of different sizes, thereby enabling broadband detection of the device.

[0062] like Figure 4As shown, each microcavity unit 100 includes an upper metal electrode 5, an epitaxial layer 10 of a quantum well detector disposed on the lower surface of the upper metal electrode 5, and a common lower metal electrode plate 2 on which the epitaxial layer 10 of the quantum well detector is disposed, the lower metal electrode plate 2 being disposed on the upper surface of the substrate 1. As an example, the epitaxial layer 10 of the quantum well detector includes an upper contact layer 7, an active region 4, and a lower contact layer 8 connected sequentially from top to bottom, and the geometric dimensions of the epitaxial layer 10 are the same as the geometric dimensions of the upper metal electrode 5, wherein the active region 4 includes a semiconductor superlattice structure of alternating GaAs and AlGaAs growth. The upper metal electrode 5 in the microcavity unit 100 is a subwavelength fractal patch antenna. The upper metal electrode 5 and the lower metal electrode plate 2 are made of metals that can form ohmic contacts with semiconductors. For example, they can be made of unalloyed Ti and Au or continuously grown Pd, Ge, Ti and Au. Choosing the latter will be more conducive to the upper metal electrode 5 and the lower metal electrode plate 2 forming good ohmic contacts with the upper contact layer 7 and the lower contact layer 8 of the epitaxial layer, respectively.

[0063] like Figure 4 As shown, a passivation layer 3 is also disposed on the surface of the lower metal electrode plate 2 of the microcavity unit. The passivation layer 3 fills the spaces between the multiple microcavity units 100 and in the first groove 101 and the second groove 102 to prevent leakage current in the active region 4. The thickness of the passivation layer 3 is equal to the thickness of the epitaxial layer 10, and its material can be SiO2 or Si3N4. A back gold layer 9 is also disposed on the back side of the substrate 1 to enable the coupling structure to be more firmly bonded to the heat sink and to improve its heat dissipation. As an example, the material of the back gold layer 9 is the same as that of the upper metal electrode 5, such as unalloyed Ti and Au or continuously grown Pd, Ge, Ti and Au.

[0064] The number of microcavity units 100 arranged in an array can be designed as needed in both the horizontal and vertical directions of the array. In this embodiment, in order to... Figure 1 The quantum well detector shown in the figure employs a conventional 45° beveled polished substrate coupling structure. In contrast, the sum of the upper surface areas of the active regions 122 in the multiple microcavity units 100 is equal to the photosensitive area of ​​the 45° coupled structure THz QWPs.

[0065] Reference Figure 2 and Figure 3 As shown, in the second direction (i.e., the Y direction shown in the figure), multiple microcavity units 100 are connected in series via microcavity connecting lines 6, which further connect the multiple microcavity units 100 to an external circuit. As an example, the material of the microcavity connecting lines 6 is selected to be a conductive material, such as the same material as the upper metal electrode 5, for example, unalloyed Ti and Au or continuously grown Pd, Ge, Ti and Au.

[0066] Example 2

[0067] This embodiment provides a method for fabricating a broadband microcavity array coupling structure for a quantum well detector, comprising the following steps:

[0068] S1: Provide a sample material layer, which includes a first substrate and an epitaxial layer from bottom to top;

[0069] like Figure 5 As shown, a first substrate 110 made of semi-insulating GaAs is provided, and a GaAs buffer layer (not shown), an etch stop layer 111, and an epitaxial layer 10 of a quantum well detector are sequentially grown from bottom to top on the upper surface of the first substrate 110. The epitaxial layer 10 includes an N-type doped lower contact layer, an active region, and an N-type doped upper contact layer (not shown). As an example, the material of the etch stop layer 111 can be AlGaAs.

[0070] S2: Provide a second substrate, form a first metal material layer on the surface of the epitaxial layer of the sample material layer, and form a second metal material layer on the surface of the second substrate;

[0071] like Figure 6 As shown, a second substrate 210 made of N+ type GaAs is provided as substrate 1 in the coupling structure, and the planar geometry of the second substrate 210 is larger than the planar geometry of the first substrate 110.

[0072] Next, refer to Figure 5 and Figure 6 As shown, in step S1, the epitaxial layer 10 and the upper surface of the second substrate 210 are respectively formed by electron beam evaporation (or magnetron sputtering) to form a first metal material layer 112 and a second metal material layer 211. As an example, both the first metal material layer 112 and the second metal material layer 211 can be made of unalloyed Ti and Au or of continuously grown Pd, Ge, Ti and Au, preferably of continuously grown Pd, Ge, Ti and Au.

[0073] S3: Press and bond the first metal material layer and the second metal material layer to form the lower metal electrode plate;

[0074] like Figure 7 As shown, the first metal material layer 112 and the second metal material layer 211 are pressed and bonded for no less than 20 minutes at a temperature of 320°C and a pressure of 8 MPa to form the lower metal electrode plate in the coupling structure.

[0075] S4: Remove the first substrate to expose the epitaxial layer, and form an upper metal electrode on the surface of the epitaxial layer;

[0076] like Figure 8 As shown, after the first substrate 110 is thinned by a grinding and polishing machine, the remaining first substrate 110 and the etch barrier layer 111 are etched away by a wet etching solution to expose the N-type doped lower contact layer in the epitaxial layer 10 in step S1, which serves as the upper contact layer of the epitaxial layer 10. At this time, the N-type doped upper contact layer in the epitaxial layer 10 in step S1 serves as the lower contact layer of the epitaxial layer 10.

[0077] Next, an upper metal electrode 5 in the coupling structure is formed on the upper surface of the epitaxial layer 10 by electron beam evaporation (or magnetron sputtering). As an example, the upper metal electrode 5 can be made of unalloyed Ti and Au or continuously grown Pd, Ge, Ti and Au. Choosing the latter will be more conducive to the formation of a good ohmic contact between the upper metal electrode 5 and the upper contact layer of the epitaxial layer.

[0078] S5: Etch the upper metal electrode and the epitaxial layer to form multiple microcavity units in the coupling structure, wherein the microcavity unit is the microcavity unit described in Embodiment 1;

[0079] Next, a patch antenna array pattern is photolithographically patterned on the upper surface of the upper metal electrode 5, and a photoresist mask is used to etch and form multiple microcavity units 100 and microcavity interconnects 6 in the coupling structure. As an example, the structure of the microcavity units and microcavity interconnects can be referred to the description in Embodiment 1, and will not be repeated here.

[0080] S6: A passivation layer is formed by filling the spaces between the multiple microcavity units and in the grooves of the microcavity units, and a microcavity connection line is deposited on the surface of the passivation layer to connect the multiple microcavity units to an external power source.

[0081] Reference Figure 4 As shown, a passivation layer 3 is formed between multiple microcavity units and in the grooves of the microcavity units to prevent leakage current in the active region 4. The thickness of the passivation layer 3 is equal to the thickness of the epitaxial layer 10, and its material can be SiO2 or Si3N4.

[0082] Next, microcavity interconnects 6 are deposited on the surface of the passivation layer 3 to connect the plurality of microcavity units to an external power source. As an example, the material of the microcavity interconnects 6 is selected to be a conductive material, such as the same material as the upper metal electrode 5, for example, unalloyed Ti and Au or continuously grown Pd, Ge, Ti and Au.

[0083] Next, the second substrate 210 is thinned, and a back gold layer 9 is formed on the side away from the lower metal electrode plate 2 to enable the coupling structure to adhere more firmly to the heat sink and improve its heat dissipation. As an example, the material of the back gold layer 9 can be unalloyed Ti and Au or continuously grown Pd, Ge, Ti and Au.

[0084] Next, a high-temperature rapid annealing process is performed at a temperature of not less than 350°C for no less than 30 seconds to ensure that the upper metal electrode 5 and the lower metal electrode plate 2 in the coupling structure form a good ohmic contact, effectively suppressing the dark current of the quantum well detector.

[0085] Finally, the components are dissected, gold wires are soldered, and the components are packaged, thus completing the fabrication of the coupling structure.

[0086] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A broadband microcavity array coupling structure for quantum well detectors, characterized in that, Includes: a substrate, and a plurality of microcavity units arranged in a uniform array above the substrate. The plurality of microcavity units have N columns in a first direction and M rows in a second direction perpendicular to the first direction, where N > 1 and M > 1, and the first side length of the microcavity unit in the first direction is L. i In the arrangement direction of the microcavity units, the first side length L of the plurality of microcavity units i Gradually increase, where 2≤i≤N; The microcavity unit includes: an epitaxial layer and an upper metal electrode disposed on the surface of the epitaxial layer, wherein the geometric dimensions of the epitaxial layer are the same as those of the upper metal electrode; all the microcavity units also include: a common lower metal electrode plate on which the epitaxial layer is disposed, wherein the lower metal electrode plate is disposed on the surface of the substrate; Furthermore, each of the microcavity units has a groove extending from the edge of the microcavity unit toward the center. The groove includes a first groove extending along the first direction and a second groove extending along the second direction. The first groove is symmetrically distributed along the central axis of symmetry of the microcavity unit in the second direction, and the second groove is symmetrically distributed along the central axis of symmetry of the microcavity unit in the first direction. The first groove and the second groove make the middle region of the microcavity unit a continuous region.

2. The broadband microcavity array coupling structure for quantum well detectors according to claim 1, characterized in that, In the first direction, the first side length L of the plurality of microcavity units i Satisfy L i -L i-1 =1μm, 2≤i≤N.

3. The broadband microcavity array coupling structure for quantum well detectors according to claim 1, characterized in that, Along the second direction, the width of the first groove is W. j `, W j `-W j-1 `=2μm, 2≤j≤M.

4. The broadband microcavity array coupling structure for a quantum well detector according to claim 1, characterized in that, In the first direction, the first depth of the first groove is de i The first span distance of the continuous region in the first direction is d, and d=L i -2*de i The first depth of the plurality of microcavity units gradually increases in the arrangement direction of the microcavity units.

5. The broadband microcavity array coupling structure for a quantum well detector according to claim 4, characterized in that, The first span distance d is a fixed value.

6. The broadband microcavity array coupling structure for a quantum well detector according to claim 1, characterized in that, The upper metal electrode is a subwavelength fractal patch antenna.

7. The broadband microcavity array coupling structure for a quantum well detector according to claim 1, characterized in that, In the second direction, the plurality of microcavity units are connected in series via microcavity connecting lines.

8. The broadband microcavity array coupling structure for a quantum well detector according to claim 1, characterized in that, The surface of the lower metal electrode plate is further provided with a passivation layer, which fills the spaces between the plurality of microcavity units and the grooves, and the thickness of the passivation layer is equal to the thickness of the epitaxial layer.

9. The broadband microcavity array coupling structure for a quantum well detector according to claim 1, characterized in that, A metal layer is also provided on the back side of the substrate.

10. A method for fabricating a broadband microcavity array coupling structure for a quantum well detector, used to fabricate the broadband microcavity array coupling structure for a quantum well detector as described in any one of claims 1-9, characterized in that, The preparation method includes the following steps: S1: Provide a sample material layer, which includes a first substrate and an epitaxial layer from bottom to top; S2: Provide a second substrate, form a first metal material layer on the surface of the epitaxial layer of the sample material layer, and form a second metal material layer on the surface of the second substrate; S3: Press and bond the first metal material layer and the second metal material layer to form the lower metal electrode plate; S4: Remove the first substrate to expose the epitaxial layer, and form an upper metal electrode on the surface of the epitaxial layer; S5: Etch the upper metal electrode and the epitaxial layer to form multiple microcavity units in the coupling structure; S6: A passivation layer is formed by filling the spaces between the multiple microcavity units and in the grooves of the microcavity units, and a microcavity connection line is deposited on the surface of the passivation layer to connect the multiple microcavity units to an external power source.

11. The method for fabricating a broadband microcavity array coupling structure for a quantum well detector according to claim 10, characterized in that, Step S6 is followed by thinning the second substrate and forming a back gold layer on the side of the second substrate away from the lower metal electrode plate.

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