阅读说明：本技术 一种红外探测器 (Infrared detector ) 是由 黄文祥 于 2020-12-11 设计创作，主要内容包括：本申请实施例公开了一种红外探测器,由多个级联台阶构成,每一级联台阶包括电子势垒结构、超晶格吸收结构和空穴势垒结构,所述级联台阶位于所述光学谐振腔内,在进行探测时,如果入射光进入该光学谐振腔,入射光在光学谐振腔的第一反射镜和第二反射镜之间进行多次反射,以使得该入射光能够多次通过超晶格吸收结构,发生共振,以增强超晶格吸收结构对该入射光的吸收,从而大幅度提高该红外探测器的量子效率,进而提高所述红外探测器的探测率。(The embodiment of the application discloses infrared detector comprises a plurality of cascade steps, and each cascade step includes electron barrier structure, superlattice absorption structure and hole barrier structure, cascade step is located in the optics resonant cavity, when surveying, if incident light gets into this optics resonant cavity, incident light carries out multiple reflection between the first speculum of optics resonant cavity and second mirror to make this incident light can pass through superlattice absorption structure many times, take place resonance, with the absorption of reinforcing superlattice absorption structure to this incident light, thereby improve this infrared detector's quantum efficiency by a wide margin, and then improve infrared detector's detectivity.)

1. An infrared detector, comprising:

a substrate;

the buffer layer is positioned on the surface of the substrate;

the optical resonant cavity is positioned on the side, away from the substrate, of the buffer layer and is composed of a first reflector, a second reflector and a gap between the first reflector and the second reflector;

a plurality of cascade steps between the first mirror and the second mirror, the cascade steps including a stacked electron barrier structure, a superlattice absorption structure, and a hole barrier structure.

2. The infrared detector as set forth in claim 1, wherein the superlattice absorption structure of each of said cascaded steps is located at an antinode of said optical cavity.

3. The infrared detector as claimed in claim 1 or 2, wherein said first mirror is located between said plurality of cascaded steps and said buffer layer, and said second mirror is located on a side of said plurality of cascaded steps facing away from said buffer layer.

4. The infrared detector as set forth in claim 3, wherein said first mirror is a bragg mirror.

5. The infrared detector according to claim 4, wherein if an incident light is incident from a side of the optical resonator away from the substrate, the first mirror includes a plurality of AlAsSb layers and a plurality of GaSb layers, the plurality of AlAsSb layers included in the first mirror and the plurality of GaSb layers included in the first mirror are alternately arranged, wherein the number of AlAsSb layers included in the first mirror ranges from 9 layers to 15 layers, and the number of GaSb layers included in the first mirror ranges from 9 layers to 15 layers.

6. The infrared detector of claim 4, further comprising: a first contact layer on a side of the plurality of cascaded steps facing away from the substrate.

7. The infrared detector of claim 4, wherein the second mirror is multiplexed as the first contact layer.

8. The infrared detector of claim 7, further comprising:

the first spacing layers and the cascade steps are arranged alternately, and the first spacing layers are positioned between two adjacent cascade steps;

a second spacer layer between the second mirror and the plurality of cascaded steps.

9. The infrared detector of claim 8, further comprising: and the first transition layer is positioned between the second interlayer and the second reflector and is a multiple quantum well transition layer.

10. The infrared detector according to claim 4, wherein if incident light is incident from one side of the substrate, the first mirror includes a plurality of AlAsSb layers and a plurality of GaSb layers, the plurality of AlAsSb layers included in the first mirror and the plurality of GaSb layers included in the first mirror are alternately arranged, wherein the number of AlAsSb layers included in the first mirror ranges from 5 layers to 7 layers, and the number of GaSb layers included in the first mirror ranges from 5 layers to 7 layers.

11. The infrared detector as claimed in claim 10, wherein said second mirror comprises a layer of Ag, said second mirror having a reflectivity of 90% or more.

12. The infrared detector of claim 10, further comprising: a second contact layer between the plurality of cascaded steps and the second mirror.

13. The infrared detector of claim 10, further comprising:

the third interlayer layers and the cascade steps are alternately arranged, and the third interlayer layers are positioned between two adjacent cascade steps;

a fourth spacer layer on a side of the plurality of cascaded steps toward the substrate.

14. The infrared detector of claim 3, further comprising: the fault-tolerant layer is positioned between the first reflector and the cascade step and comprises a first sub fault-tolerant layer and a second sub fault-tolerant layer, the first sub fault-tolerant layer is a GaSb layer, the second sub fault-tolerant layer is a superlattice fault-tolerant layer, the second sub fault-tolerant layer comprises a plurality of layers of AlInSb layers and a plurality of layers of InAs layers, and the plurality of layers of AlInSb layers and the plurality of layers of InAs layers of the second sub fault-tolerant layer are alternately arranged.

15. The infrared detector of claim 1, wherein the electron barrier structure comprises a plurality of first quantum wells comprising stacked layers of AlSb and GaSb;

the superlattice absorption structure comprises a plurality of InAs layers and a plurality of GaSb layers, wherein the plurality of InAs layers included in the superlattice absorption structure and the plurality of GaSb layers included in the superlattice absorption structure are alternately arranged;

the hole barrier structure comprises a plurality of second quantum wells, and each second quantum well comprises a stacked AlSb layer and an InAs layer.

16. The infrared detector of claim 1, further comprising: and the first metal electrode is positioned on one side of the optical resonant cavity, which faces away from the substrate.

Technical Field

The application relates to the technical field of infrared detection, in particular to an infrared detector.

Background

With the development of infrared detection technology, the demand of high-performance infrared detectors is more and more urgent. The infrared detector which is most widely applied at present is a mercury cadmium telluride infrared detector, however, the mercury cadmium telluride material has higher Auger recombination rate, smaller electron effective mass and higher tunneling current, thereby limiting the improvement of the performance of the infrared detector.

In contrast, researchers are always searching better materials to apply to infrared detectors, and the researchers find that the conduction band bottom of InAs in InAs/GaSb second-class superlattice materials is lower than the valence band top of GaSb, the band gap of the special energy band structure can cover the whole intermediate infrared range (3 mu m-30 mu m), and the materials can be specifically applied only by changing the thicknesses of the InAs and the GaSb. In addition, compared with a mercury cadmium telluride material, the InAs/GaSb superlattice has lower Auger recombination rate, larger electron effective mass and higher tunneling current. In addition, since Smith and Mailhot put forward that InAs/GaSb second-class superlattice materials are applied to infrared detectors in 1987, many people have devoted to research on InAs/GaSb second-class superlattice infrared detectors, and the research on infrared detectors based on the materials has been vigorously developed in nearly two decades, and the InAs/GaSb second-class superlattice materials are already representative materials of third-generation infrared focal plane detectors at present. However, the detection rate of the infrared detector is low at present.

Disclosure of Invention

In order to solve the above technical problem, an embodiment of the present application provides an infrared detector, which combines a plurality of cascade steps and a resonant cavity to improve the utilization rate of incident light, obtain higher quantum efficiency, and thus improve the detection rate of the infrared detector.

In order to solve the above problem, the embodiment of the present application provides the following technical solutions:

an infrared detector, comprising:

a substrate;

the buffer layer is positioned on the surface of the substrate;

the optical resonant cavity is positioned on the side, away from the substrate, of the buffer layer and is composed of a first reflector, a second reflector and a gap between the first reflector and the second reflector;

a plurality of cascade steps between the first mirror and the second mirror, the cascade steps including a stacked electron barrier structure, a superlattice absorption structure, and a hole barrier structure.

Optionally, the superlattice absorption structure of each of the cascaded steps is located on an antinode of the optical resonant cavity.

Optionally, the first mirror is located between the plurality of cascaded steps and the buffer layer, and the second mirror is located on a side of the plurality of cascaded steps facing away from the buffer layer.

Optionally, the first mirror is a bragg mirror.

Optionally, if the incident light is incident from a side of the optical resonator far from the substrate, the first reflector includes a plurality of AlAsSb layers and a plurality of GaSb layers, the plurality of AlAsSb layers included in the first reflector and the plurality of GaSb layers included in the first reflector are alternately arranged, wherein a value range of a number of layers of the AlAsSb layers included in the first reflector is 9-15 layers, and a value range of a number of layers of the GaSb layers included in the first reflector is 9-15 layers.

Optionally, the method further includes: a first contact layer on a side of the plurality of cascaded steps facing away from the substrate.

Optionally, the second mirror is reused as the first contact layer.

Optionally, the method further includes:

the first spacing layers and the cascade steps are arranged alternately, and the first spacing layers are positioned between two adjacent cascade steps;

a second spacer layer between the second mirror and the plurality of cascaded steps.

Optionally, the method further includes: and the first transition layer is positioned between the second interlayer and the second reflector and is a multiple quantum well transition layer.

Optionally, if incident light enters from one side of the substrate, the first reflector includes a plurality of AlAsSb layers and a plurality of GaSb layers, the plurality of AlAsSb layers included in the first reflector and the plurality of GaSb layers included in the first reflector are alternately arranged, wherein the number of AlAsSb layers included in the first reflector ranges from 5 to 7, and the number of GaSb layers included in the first reflector ranges from 5 to 7.

Optionally, the second reflector comprises an Ag layer, and the reflectivity of the second reflector is greater than or equal to 90%.

Optionally, the method further includes: a second contact layer between the plurality of cascaded steps and the second mirror.

Optionally, the method further includes:

the third interlayer layers and the cascade steps are alternately arranged, and the third interlayer layers are positioned between two adjacent cascade steps;

a fourth spacer layer on a side of the plurality of cascaded steps toward the substrate.

Optionally, the method further includes: the fault-tolerant layer is positioned between the first reflector and the cascade step and comprises a first sub fault-tolerant layer and a second sub fault-tolerant layer, the first sub fault-tolerant layer is a GaSb layer, the second sub fault-tolerant layer is a superlattice fault-tolerant layer, the second sub fault-tolerant layer comprises a plurality of layers of AlInSb layers and a plurality of layers of InAs layers, and the plurality of layers of AlInSb layers and the plurality of layers of InAs layers of the second sub fault-tolerant layer are alternately arranged.

Optionally, the electron barrier structure includes a plurality of first quantum wells, and the first quantum wells include stacked AlSb layers and GaSb layers;

the superlattice absorption structure comprises a plurality of InAs layers and a plurality of GaSb layers, wherein the plurality of InAs layers included in the superlattice absorption structure and the plurality of GaSb layers included in the superlattice absorption structure are alternately arranged;

the hole barrier structure comprises a plurality of second quantum wells, and each second quantum well comprises a stacked AlSb layer and an InAs layer.

Optionally, the method further includes: and the first metal electrode is positioned on one side of the optical resonant cavity, which faces away from the substrate.

Compared with the prior art, the technical scheme has the following advantages:

in the infrared detector that this application embodiment provided, including a plurality of cascade steps, cascade the step and include electron barrier structure, superlattice absorption structure and hole barrier structure, cascade the step and be located in the optical resonator, when surveying, if incident light gets into this optical resonator, incident light carries out multiple reflection between optical resonator's first speculum and second mirror to make this incident light can pass through superlattice absorption structure many times, take place resonance, with the absorption of reinforcing superlattice absorption structure to this incident light, thereby improve this infrared detector's quantum efficiency by a wide margin, and then improve infrared detector's detectivity.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic structural diagram of an infrared detector provided in an embodiment of the present application;

fig. 2 is a schematic structural diagram of an infrared detector according to another embodiment of the present application;

fig. 3 is a schematic structural diagram of an infrared detector according to another embodiment of the present application;

fig. 4 is a schematic diagram of refractive indexes of a partial structure in a simulated infrared detector corresponding to the infrared detector provided in an embodiment of the present application, and a schematic diagram of distribution of a light field of incident light entering the simulated infrared detector;

fig. 5 is a schematic structural diagram of an infrared detector according to yet another embodiment of the present application;

fig. 6 is a schematic diagram of refractive indexes of a partial structure in a simulated infrared detector corresponding to an infrared detector provided in another embodiment of the present application, and a schematic diagram of distribution of a light field of incident light entering the simulated infrared detector.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application, but the present application may be practiced in other ways than those described herein, and it will be apparent to those of ordinary skill in the art that the present application is not limited to the specific embodiments disclosed below.

Next, the present application will be described in detail with reference to the drawings, and in the detailed description of the embodiments of the present application, the cross-sectional views illustrating the structure of the device are not enlarged partially according to the general scale for convenience of illustration, and the drawings are only examples, which should not limit the scope of the protection of the present application. In addition, the three-dimensional dimensions of length, width and depth should be included in the actual fabrication.

The interband cascade detector based on the second type of superlattice can overcome the limitation of diffusion length, the interband cascade detector of the second type of superlattice can almost completely collect photon-generated carriers, and meanwhile, the multistage cascade steps included in the interband cascade detector can effectively reduce noise, so that the interband cascade detector of the second type of superlattice can work at high temperature. Each cascade step comprises an electron barrier, a hole barrier and an absorption region formed by two types of superlattices, and no depletion layer is arranged, so that the tunneling current and the generated recombination current of the cascade step can be greatly reduced. Moreover, the complementary barrier structure can achieve the self-passivation effect, and solve the problem of surface leakage current, especially for the second type of superlattice detectors, the surface leakage current is one of the main factors limiting the performance of the detector. In addition, the special multi-stage cascade detector can be realized by the molecular beam epitaxy growth technology of mature III-V compounds. Therefore, the interband cascade detector of the two types of superlattices has great application advantages.

However, the detection rate of the band-to-band cascade detector of the two types of superlattices is low at present, and the inventor researches and discovers that the detection rate is caused by the InAs/GaSb type two superlatticesIn the crystal lattice, electrons are limited in an InAs layer, holes are limited in a GaSb layer, and the electrons and the holes are separated in space, so that the absorption coefficient of the InAs/GaSb secondary superlattice is low. For example, near the band gap, the absorption coefficients of the superlattice for medium and long waves measured experimentally are close to 3000cm respectively^-1And 2000cm^-1. Due to the limit of the absorption coefficient of InAs/GaSb type II superlattices and the short diffusion length (less than 2 μm at room temperature), the quantum efficiency of the superlattice detector is low. The quantum efficiency of the PIN superlattice detector reported in the literature at present is mostly lower than 30%, and particularly for an interband cascade detector, the absorption region of the interband cascade detector is thin, so that the quantum efficiency of the interband cascade detector is lower than 10%, and the detection rate of the interband cascade detector is lower.

Based on the above research, as shown in fig. 1, an embodiment of the present application provides an infrared detector, including:

a substrate 10;

a buffer layer 20 on the surface of the substrate 10;

an optical resonant cavity 30 located on a side of the buffer layer 20 facing away from the substrate 10, the optical resonant cavity 30 being formed by a first mirror 31, a second mirror 32 and a gap between the first mirror 31 and the second mirror 32;

a plurality of cascade steps 40 between the first mirror 31 and the second mirror 32, the cascade steps 40 sequentially including an electron barrier structure 41, a superlattice absorption structure 42, and a hole barrier structure 43.

It should be noted that, in the embodiment of the present application, the infrared detector is an interband cascade infrared detector.

It should be noted that, in the embodiment of the present application, the optical resonant cavity is a fabry-perot resonant cavity, and in other embodiments of the present application, the optical resonant cavity may also be another type of resonant cavity, which is not limited in this application, as the case may be.

Optionally, in an embodiment of the present application, the substrate is a GaSb substrate, and in other embodiments of the present application, the substrate may also be a substrate made of another material, which is not limited in this application, as the case may be.

On the basis of the above embodiments, in one embodiment of the present application, the buffer layer is a GaSb buffer layer, and in other embodiments of the present application, the buffer layer may also be a buffer layer made of other materials, which is not limited in this application, as the case may be. It should be noted that, in the embodiment of the present application, the buffer layer may be an undoped buffer layer, and in other embodiments of the present application, the buffer layer may also be a doped buffer layer, which is not limited in this application, and is determined as the case may be.

The infrared detector that this application embodiment provided, including a plurality of cascade steps, cascade the step and include electron barrier structure, superlattice absorption structure and hole barrier structure, cascade the step and be located in the optical resonator, when surveying, if incident light gets into this optical resonator, incident light carries out multiple reflection between optical resonator's first speculum and second mirror to make this incident light can pass through superlattice absorption structure many times, take place resonance, with the absorption of reinforcing superlattice absorption structure to this incident light, thereby improve this infrared detector's quantum efficiency by a wide margin, and then improve infrared detector's detectivity.

On the basis of any one of the above embodiments, in an embodiment of the present application, the infrared detector includes 2 to 10 cascade steps, so that the infrared detector utilizes the cascade steps, thereby effectively reducing noise, improving signal-to-noise ratio, and simultaneously improving the working temperature of the infrared detector.

It should be noted that, in the embodiment of the present application, the resonant wavelengths of different optical resonant cavities are different, and the standing waves formed by different resonant wavelengths are different, so that the positions of the antinodes of different standing waves are also different, and therefore, the resonant wavelength of the resonant cavity needs to be determined first, so as to determine the position of the antinode of the standing wave formed by the resonant wavelength, and thus the superlattice absorption structure of the cascade step can be disposed at the position of the antinode of the standing wave, so as to increase the absorption of the incident light. Specifically, in an embodiment of the present application, the resonance wavelength is 4 μm, but this is only an example of the resonance wavelength, and the resonance wavelength provided in the embodiment of the present application is not limited, as the case may be.

Based on this, on the basis of the above embodiments, in one embodiment of the present application, the superlattice absorption structure of each of the cascaded steps is located at an antinode of the optical resonant cavity, so that the superlattice absorption structure sufficiently absorbs the resonance wavelength, that is, at the resonance wavelength, the quantum efficiency of the infrared detector is highest.

In addition, the optical resonant cavity in the application can provide better wavelength selectivity, so that the infrared detector comprising the optical resonant cavity in the application can be used in combination with a laser with corresponding wavelength, and the application range is wide, for example, the infrared detector can be applied to gas detection and energy transmission, hyperspectral imaging and multispectral imaging and other applications.

It should be noted that, in one embodiment of the present application, the thicknesses of the superlattice absorption structures of the cascaded steps are the same, so that the photocurrent between each cascaded step is close to each other, and in other embodiments of the present application, the thicknesses of the superlattice absorption structures of the cascaded steps are not exactly the same, which is not limited in the present application, as the case may be.

On the basis of any one of the embodiments, in an embodiment of the present application, the electron barrier structure includes a plurality of first quantum wells, each of which includes a stacked AlSb layer and a GaSb layer;

the superlattice absorption structure comprises a plurality of InAs layers and a plurality of GaSb layers, wherein the plurality of InAs layers included in the superlattice absorption structure and the plurality of GaSb layers included in the superlattice absorption structure are alternately arranged;

the hole barrier structure comprises a plurality of second quantum wells, and each second quantum well comprises a stacked AlSb layer and an InAs layer.

On the basis of the above embodiments, in an embodiment of the present application, the electron barrier structure includes 3 electron barriersOptionally, in this embodiment of the application, in each of the first quantum wells, a thickness of the AlSb layer ranges from 1nm to 2nm, a thickness of the GaSb layer ranges from 3nm to 8nm, a doping type of the GaSb layer is p-type doping, and a doping concentration of the GaSb layer ranges from 1 × 10¹⁵cm^-3-1×10¹⁷cm^-3。

In the embodiment of the present application, the AlSb layer included in the first quantum well is an undoped AlSb layer.

It should be further noted that, in an embodiment of the present application, the thickness of the AlSb layer in the first quantum well may be the same or may not be the same, and in another embodiment of the present application, the thickness of the GaSb layer in the first quantum well may be the same or may not be the same, which is not limited in this application, and is determined as the case may be.

Specifically, on the basis of the above embodiments, in an embodiment of the present application, the thickness of the GaSb layer in the plurality of first quantum wells gradually decreases in a direction away from the substrate, so that the energy level of holes in the first quantum wells gradually increases, so as to make the hole transportation smoother.

On the basis of any one of the above embodiments, in an embodiment of the present application, the superlattice absorption structure is an InAs/GaSb type two-layer superlattice absorption structure, the number of layers of an InAs layer included in the superlattice absorption structure ranges from 20 layers to 60 layers, and the number of layers of a GaSb layer included in the superlattice absorption structure ranges from 20 layers to 60 layers, where the number of layers of an InAs layer included in the superlattice absorption structure is the same as the number of layers of a GaSb layer included in the superlattice absorption structure.

Optionally, in an embodiment of the present application, a thickness of the InAs layer included in the superlattice absorption structure ranges from 1nm to 4nm, a doping type of the InAs layer included in the superlattice absorption structure is p-type, and a doping concentration of the InAs layer ranges from 1 × 10¹⁵cm^-3-1×10¹⁷cm^-3(ii) a The superlattice absorption junctionThe thickness of the GaSb layer is 1-4 nm, the doping type of the GaSb layer is p-type, and the doping concentration of the GaSb layer is 1 x 10¹⁵cm^-3-1×10¹⁷cm^-3。

On the basis of the above embodiments, in one embodiment of the present application, the superlattice absorption structure further includes: and optionally, in an embodiment of the present application, the interface layer is an InSb layer, which is not limited in this application, and is determined as the case may be.

In one embodiment of the present application, the thicknesses of the InAs layers in the respective layers in the superlattice absorption structure may be the same or may not be the same, and in another embodiment of the present application, the thicknesses of the GaSb layers in the superlattice absorption structure may be the same or may not be the same, which is not limited in the present application, and is determined as the case may be.

In the embodiments of the present application, in addition, in the embodiments of the present application, in the superlattice absorption structure, the doping concentration of the InAs layer and the doping concentration of the GaSb layer may be the same or different, and the present application does not limit this, which is determined by the specific circumstances. Specifically, in one embodiment of the present application, in the superlattice absorption structure, the doping concentration of the InAs layer and the doping concentration of the GaSb layer are the same.

On the basis of any one of the above embodiments, in an embodiment of the present application, the hole barrier structure includes 6 to 10 second quantum wells, in the embodiment of the present application, in the second quantum wells, a thickness of the AlSb layer ranges from 1nm to 2nm, the AlSb layer is an undoped AlSb layer, and in each of the second quantum wells, a thickness of the InAs layer ranges from 3nm to 8nm, wherein at least one InAs layer of the plurality of second quantum wells is doped, a doping type of the InAs layer is n-type doping, and a doping concentration of the InAs layer ranges from 1 × 10¹⁶cm^-3-1×10¹⁸cm^-3。

In the embodiment of the present application, in the hole barrier structure, the doping concentrations of the InAs layers may be the same or different for each layer.

It should be noted that, in an embodiment of the present application, the thickness of the AlSb layer in each of the second quantum wells may be the same or may not be the same, and in another embodiment of the present application, the thickness of the InAs layer in each of the second quantum wells may be the same or may not be the same, which is not limited in the present application, and is determined as the case may be.

Specifically, on the basis of the above embodiments, in an embodiment of the present application, the thickness of the InAs layer in the plurality of second quantum wells gradually increases in a direction away from the substrate, so that the energy level of electrons in the second quantum wells gradually decreases, so that the electrons are quickly extracted from the superlattice absorption layer, and the electrons can be more quickly transferred from a high energy level to a low energy level, thereby achieving electron relaxation.

Continuing with fig. 1, based on any of the above embodiments, in an embodiment of the present application, the first mirror 31 is located between the plurality of cascaded steps 40 and the buffer layer 20, and the second mirror 32 is located on a side of the plurality of cascaded steps 40 facing away from the buffer layer 20.

As shown in fig. 2, on the basis of any of the above embodiments, in an embodiment of the present application, the infrared detector further includes: a first metal electrode 50 located on a side of the optical resonant cavity facing away from the substrate 10.

Optionally, in an embodiment of the present application, the first metal electrode is a double-layer electrode, for example, the double-layer electrode is a Ti/Au electrode, where the first metal electrode includes a Ti layer located on a side of the second mirror facing away from the substrate and an Au layer located on a side of the Ti layer facing away from the second mirror.

Optionally, in an embodiment of the present application, a thickness of the first metal electrode ranges from 200nm to 500nm, which is not limited in the present application, and is determined as the case may be.

Continuing with fig. 2, based on any of the above embodiments, in an embodiment of the present application, the infrared detector further includes:

a fault tolerant layer 60 positioned between said first mirror 31 and said cascade step 40, a surface of said fault tolerant layer 60 exposed to a side facing away from the substrate 10 forming a step;

and a second metal electrode 70 positioned at the bottom of the step, wherein the second metal electrode 70 is electrically connected with the fault-tolerant layer 60.

In the embodiments of the present application, the second metal electrode may be the same as or different from the first metal electrode, and the present application does not limit this, as the case may be.

It should be further noted that, in the embodiment of the present application, the step is formed by etching the sidewall of the cascade step by using an etching process until the surface of the fault-tolerant layer on the side away from the substrate is exposed, so that, in the step forming process, the fault-tolerant layer is used as an etching stop layer to prevent the first reflective mirror from being etched, thereby protecting the first reflective mirror. It should be further noted that, in the embodiments of the present application, the etching process includes wet etching or photolithography, which is not limited in this application, as the case may be.

As shown in fig. 2, based on any of the above embodiments, in an embodiment of the present application, the fault-tolerant layer 60 includes a first sub fault-tolerant layer 61 and a second sub fault-tolerant layer 62, the first sub fault-tolerant layer 61 is a GaSb layer, and the second sub fault-tolerant layer 62 is a superlattice fault-tolerant layer, optionally, in an embodiment of the present application, the second sub fault-tolerant layer 62 includes multiple AlInSb layers and multiple InAs layers, and the multiple AlInSb layers included in the second sub fault-tolerant layer 62 and the multiple InAs layers included in the second sub fault-tolerant layer are alternately arranged.

On the basis of the above embodiments, in an embodiment of the present application, the thickness of the first sub-fault-tolerant layer ranges from 200nm to 300nm, the doping type of the first sub-fault-tolerant layer is p-type, and the doping concentration ranges from 1 × 10¹⁶cm^-3-1×10¹⁸cm^-3The thickness of the second sub-fault-tolerant layer ranges from 200nm to 300nm, the doping type of the InAs layer in the second sub-fault-tolerant layer is n type, and the doping concentration ranges from 1 x 10¹⁶cm^-3-1×10¹⁸cm^-3。

It should be noted that, in the embodiment of the present application, doping of the first sub fault-tolerant layer is doping of a surface of a side of the first sub fault-tolerant layer facing the second sub fault-tolerant layer, and an AlInSb layer in the second sub fault-tolerant layer is an undoped AlInSb layer.

Optionally, in an embodiment of the present application, the chemical formula of AlInSb in the superlattice fault-tolerant layer is AlIn_0.3Sb_0.7The chemical formula of InAs in the superlattice fault-tolerant layer is InAs, and in other embodiments of the present application, the chemical formula of AlInSb in the superlattice fault-tolerant layer may also be in other forms.

Optionally, in an embodiment of the present application, the fault-tolerant layer further includes: and the second transition layer is positioned between the first sub fault-tolerant layer and the second sub fault-tolerant layer so as to ensure that electrons are transmitted more smoothly.

Optionally, in an embodiment of the present application, the second transition layer is a multiple quantum well layer composed of multiple AlInSb layers and multiple InAs layers, the multiple AlInSb layers included in the second transition layer and the multiple InAs layers included in the second transition layer are overlapped, and in other embodiments of the present application, the second transition layer may also be a transition layer of another material, which is not limited in this application, and is determined as the case may be.

In addition, in the embodiments of the present application, the inventors can classify the infrared detector into two types according to whether the incident light is incident from the side of the optical resonant cavity away from the substrate or directly from the substrate side.

We will first describe an infrared detector in which incident light is incident from a side of the optical resonant cavity away from the substrate as an example.

As shown in fig. 3, on the basis of any of the above embodiments, in one embodiment of the present application, the first mirror 31 is a bragg mirror, and in other embodiments of the present application, the first mirror 31 may also be another type of mirror, which is not limited in this application, as the case may be.

On the basis of the foregoing embodiment, in an embodiment of the present application, if incident light is incident from a side of the optical resonant cavity 30 away from the substrate 10, the first reflective mirror 31 includes multiple AlAsSb layers and multiple GaSb layers, where the multiple AlAsSb layers included in the first reflective mirror 31 and the multiple GaSb layers included in the first reflective mirror 31 are alternately arranged, a value range of the number of AlAsSb layers included in the first reflective mirror is 9 to 15 layers, and a value range of the number of GaSb layers included in the first reflective mirror is 9 to 15 layers. In the embodiment of the present application, the number of AlAsSb layers included in the first reflecting mirror 31 is one more layer than the number of GaSb layers included in the first reflecting mirror 31.

As shown in fig. 3, based on the above-mentioned embodiment, in an embodiment of the present application, it should be noted that, in the embodiment of the present application, a value range of a thickness of the AlAsSb layer included in the first reflecting mirror and a value range of a thickness of the GaSb layer included in the first reflecting mirror are not limited, as the case may be.

Optionally, in an embodiment of the application, the reflectivity of the first reflector is greater than or equal to 90% so as to reflect more incident light incident on the surface of the first reflector to the superlattice absorption structure, so that the superlattice absorption structure fully absorbs the incident light, thereby further improving the utilization rate of the infrared detector for the incident light, improving the conversion efficiency of the infrared detector, and further improving the detection rate of the infrared detector.

It should be noted that, in general, the dopant is not dopedThe undoped GaSb layer is p-type, wherein the undoped GaSb layer generates free carrier absorption while lowering its own refractive index, and thus the inventors n-type-dope the GaSb layer included in the first mirror. Based on this, in an embodiment of the present application, a doping type of the GaSb layer included in the first reflective mirror is n-type, and a value range of a doping concentration is 1 × 10¹⁶cm^-3-1×10¹⁷cm^-3To neutralize the background hole concentration of the GaSb layer included in the first mirror, thereby eliminating free carrier absorption in the GaSb layer while increasing its own refractive index.

Optionally, in an embodiment of the present application, the chemical formula of AlAsSb in the first mirror is AlAs_0.08Sb_0.92The chemical formula of GaSb in the first reflecting mirror is GaSb, and in other embodiments of the present application, the chemical formula of AlAsSb in the first reflecting mirror may also be in other forms.

On the basis of any one of the above embodiments, in an embodiment of the present application, the infrared detector further includes: and the first contact layer is positioned on one side of the plurality of cascading steps, which faces away from the substrate, and is used for forming good ohmic contact with the first metal electrode. It should be noted that, in an embodiment of the present application, the first contact layer may be located in the optical resonant cavity, specifically, the first contact layer is located between the plurality of cascaded steps and the second mirror, and in other embodiments of the present application, the first contact layer may also be located outside the optical resonant cavity, specifically, the first contact layer is located on a side of the second mirror facing away from the substrate, which is not limited in this application, as the case may be.

In addition to any of the above embodiments, in an embodiment of the present application, the first contact layer is an InAs contact layer, and in other embodiments of the present application, the first contact layer may also be a contact layer of another material, which is not limited in this application, as the case may be.

On the basis of any one of the above embodiments, in one embodiment of the application, theThe thickness of the first contact layer ranges from 10nm to 30nm, the doping type of the first contact layer is n-type, and the doping concentration of the first contact layer ranges from 1 × 10¹⁷cm^-3-1×10¹⁹cm^-3。

In other embodiments of the present application, the second mirror may be directly reused as the first contact layer without adding an additional first contact layer, so that the structure of the infrared detector may be simplified.

Based on this, in another embodiment of the present application, the second mirror is reused as the first contact layer, that is, the second mirror is the first contact layer, so that the second mirror and the first metal electrode form a good ohmic contact, and an additional first contact layer is not required to be added, so that the structure of the infrared detector can be simplified.

It should be noted that, in the embodiment of the present application, the reflectivity of the second reflecting mirror should not be too high, and should not be too low, if the reflectivity of the second reflecting mirror is too high, when the incident light that enters the second reflecting mirror from the outside enters the second reflecting mirror, the second reflecting mirror can highly reflect the incident light, so as to reduce the incidence rate of the incident light, so that the incident light that enters the optical resonant cavity is less, and the utilization rate of the incident light is reduced; if the reflectivity of the second reflector is too low, when the incident light reflected back from the first reflector is reflected to the second reflector, the second reflector can highly transmit the incident light, so that the reflectivity of the incident light is reduced, the incident light is less reflected to the superlattice absorption area, and the utilization rate of the incident light is reduced. Based on any of the above embodiments, in an embodiment of the present application, the reflectivity of the second mirror ranges from 30% to 70%.

In other embodiments of the present application, the second mirror may also be a bragg mirror located on a side of the first contact layer facing away from the substrate, which is not limited in this application, as the case may be.

Continuing with fig. 3, on the basis of any of the above embodiments, in an embodiment of the present application, the method further includes: a plurality of first spacing layers 80, wherein the plurality of first spacing layers 80 and the plurality of cascade steps 40 are alternately arranged, and the first spacing layers 80 are located between two adjacent cascade steps 40, so that the cascade steps 40 are located on an antinode of the optical resonant cavity 30. Note that, in the embodiment of the present application, the first spacing layer 80 is located between adjacent antinodes.

Optionally, in an embodiment of the present application, the first spacer layer is a GaSb layer, which is not limited in the present application, as the case may be.

Optionally, in an embodiment of the present application, a thickness of the first spacer layer is 200nm to 350nm, a doping type of the first spacer layer is p-type, and a doping concentration of the first spacer layer ranges from 1 × 10¹⁶cm^-3-1×10¹⁸cm^-3。

Continuing with fig. 3, based on the above-mentioned embodiment, in an embodiment of the present application, the infrared detector further includes: a second spacer layer 90, the second spacer layer 90 being located between the second mirror 32 and the plurality of cascaded steps 40. It should be noted that, in the embodiment of the present application, the first spacing layer 80 and the second spacing layer 90 may be the same or different, and specifically, in an embodiment of the present application, the first spacing layer 80 and the second spacing layer 90 are the same.

It should also be noted that in the embodiments of the present application, the second spacer layer is located between adjacent antinodes.

Continuing with fig. 3, based on the above-mentioned embodiment, in an embodiment of the present application, the infrared detector further includes: a first transition layer 100 between the second spacer layer 90 and the second mirror 32 to allow the electrons to be more smoothly transferred from the second spacer layer 90 to the second mirror 32, i.e., equivalent to reducing the electrical resistance between the second spacer layer 90 and the second mirror 32.

On the basis of the above embodiments, in an embodiment of the present application, the first transition layer is a multiple quantum well transition layer, the multiple quantum well transition layer includes a plurality of third quantum wells, and the third quantum wells include stacked AlInSb layers and InAs layers.

On the basis of the above embodiments, in an embodiment of the present application, the multiple quantum well transition layer includes 2 to 3 third quantum wells, and in the embodiment of the present application, in the third quantum well, a thickness of the AlInSb layer ranges from 1nm to 2nm, and a thickness of the InAs layer ranges from 9nm to 10 nm.

In an embodiment of the present application, in the third quantum well, the chemical formula of AlInSb is AlIn_0.3Sb_0.7In other embodiments of the present application, the chemical formula of InAs in the third quantum well may be in other forms.

The following describes, in conjunction with a specific embodiment, an infrared detector provided in the present application, in which incident light is incident from a side of the optical resonant cavity away from the substrate, with a resonance wavelength (a peak wavelength of an infrared band) of 4 μm:

the infrared detector includes: the device comprises a substrate, a buffer layer, a first reflector, an error-tolerant layer, 3 cascade steps, a plurality of first spacing layers, a second spacing layer, a first transition layer, a second reflector, a first metal electrode and a second metal electrode;

the substrate is a GaSb substrate;

the buffer layer is a GaSb buffer layer, the thickness of the GaSb buffer layer is 500nm, and the GaSb buffer layer is an undoped buffer layer;

the first reflector is a Bragg reflector, and the reflectivity of the first reflector is close to 90%;

specifically, the first reflector comprises 11 AlAsSb layers and 10 GaSb layers, wherein the 11 AlAsSb layers and the 10 GaSb layers are alternately arranged, and AlAsSb (such as AlAs)_0.08Sb_0.92) The thickness of the layer is 315nm, the AlAsSb (e.g. AlAs)_0.08Sb_0.92) The layer being undoped AlAsSb (e.g. AlAs)_0.08Sb_0.92) A layer of a material selected from the group consisting of,the thickness of the GaSb layer is 263nm, the doping type of the GaSb layer is n-type, and the doping concentration is 7 multiplied by 10¹⁶cm^-3；

The fault-tolerant layer comprises a first sub-fault-tolerant layer and a second sub-fault-tolerant layer, the first sub-fault-tolerant layer is a GaSb layer, the thickness of the GaSb layer is 209nm, the surface of the GaSb layer, which is far away from the side of the substrate, is doped, the doping type is p, and the doping concentration is 2 multiplied by 10¹⁷cm^-3；

The second sub-fault-tolerant layer is AlInSb/InAs (such as AlIn)_0.3Sb_0.7InAs) a superlattice fault-tolerant layer;

specifically, the AlIn_0.3Sb_0.7the/InAs superlattice fault-tolerant layer comprises 21 layers of AlIn_0.3Sb_0.7Layer and 21 InAs layers, each layer of AlIn_0.3Sb_0.7The thickness of the layer is 1.9nm, the AlIn_0.3Sb_0.7The layer is undoped AlIn_0.3Sb_0.7Each InAs layer has a thickness of 8.1nm, a doping type of n-type and a doping concentration of 5 × 10¹⁷cm^-3；

The cascade step comprises an electron barrier structure, a superlattice absorption structure and a hole barrier structure; the electron barrier structure is composed of 4 first quantum wells, and each first quantum well comprises an AlSb layer and a GaSb layer which are stacked;

specifically, the 4 first quantum wells are sequentially a first quantum well, a second first quantum well, a third first quantum well and a fourth first quantum well from bottom to top (namely, along the direction from the substrate to the optical resonant cavity), wherein the first quantum well is composed of a layer with the thickness of 1.2nmAlSb and a layer with the thickness of 7.1nmGaSb, the second first quantum well is composed of a layer with the thickness of 1.2nmAlSb and a layer with the thickness of 6.0nmGaSb, the third first quantum well is composed of a layer with the thickness of 1.3nmAlSb and a layer with the thickness of 4.5nmGaSb, and the fourth first quantum well is composed of a layer with the thickness of 1.3nmAlSb and a layer with the thickness of 3.1 nmGaSb. In the first quantum well, all AlSb layers are undoped AlSb layers, the doping type of each GaSb layer is p-type doping, and the doping concentration is 2.4 multiplied by 10¹⁶cm^-3；

The superlattice absorption structure comprises 40 periods, wherein each period sequentially comprises an InAs layer, an InSb layer, a GaSb layer and an InSb layer;

specifically, the method comprises the following steps: in each period, the thickness of the InAs layer is 2.01nm, the thickness of the InSb layer is 0.13nm, the thickness of the GaSb layer is 2.55nm and the thickness of the InSb layer is 0.13nm, the doping types of the InAs layer, the InSb layer, the GaSb layer and the InSb layer are all p-type, and the doping concentration is 2.4 multiplied by 10¹⁶cm^-3；

The hole barrier structure is composed of 8 second quantum wells, and each second quantum well comprises an AlSb layer and an InAs layer which are stacked; the 8 second quantum wells sequentially comprise a first second quantum well, a second quantum well, a third second quantum well, a fourth second quantum well, a fifth second quantum well, a sixth second quantum well, a seventh second quantum well and an eighth second quantum well from bottom to top;

specifically, the first second quantum well is composed of a layer with the thickness of 1.7nmAlSb and a layer with the thickness of 3.1nmInAs, the second quantum well is composed of a layer with the thickness of 1.7nmAlSb and a layer with the thickness of 3.5nmInAs, the third second quantum well is composed of a layer with the thickness of 1.6nmAlSb and a layer with the thickness of 3.7nmInAs, the fourth second quantum well is composed of a layer with the thickness of 1.5nmAlSb and a layer with the thickness of 3.9nmInAs, the fifth second quantum well is composed of a layer with the thickness of 1.5nmAlSb and a layer with the thickness of 4.4nmInAs, the sixth second quantum well is composed of a layer with the thickness of 1.5nmAlSb and a layer with the thickness of 5.3nmInAs, the seventh second quantum well is composed of a layer with the thickness of 1.5nmAlSb and a layer with the thickness of 6.1nmInAs, and the eighth second quantum well is composed of 1.5 nmInAs and a layer with the thickness of 1.7 nmInAs; in the second quantum well, all AlSb layers are undoped AlSb layers, at least one InAs layer is doped, the doping type of at least one InAs layer is n-type doping, and the doping concentration is 1.5 multiplied by 10¹⁷cm^-3；

The plurality of first spacing layers and the plurality of cascade steps are alternately arranged, and the first spacing layers are positioned between two adjacent cascade steps;

specifically, the first spacing layer is a GaSb layer with the thickness of 273nm, the doping type is p-type, and the doping concentration is 2.4 multiplied by 10¹⁶cm^-3The first spacing layer is positioned onBetween adjacent antinodes;

the second spacer layer is positioned on the side, away from the substrate, of the plurality of cascading steps, the second spacer layer is identical to the first spacer layer, and the second spacer layer is positioned between adjacent antinodes;

the first transition layer is a multi-quantum well transition layer, the multi-quantum well transition layer comprises 2 third quantum wells, and the third quantum wells comprise stacked AlInSb (such as AlIn)_0.3Sb_0.7) The quantum well structure comprises a layer and an InAs layer, wherein 2 third quantum wells are a first third quantum well and a second third quantum well from bottom to top in sequence;

specifically, the first and third quantum wells are formed with a thickness of 1.5nmal in_0.3Sb_0.7A layer of 9.0nm InAs, and a second third quantum well of 1.4AlIn_0.3Sb_0.7A layer and a layer with the thickness of 9.4 nmInAs;

the second reflector (i.e. the first contact layer) is an InAs contact layer, the thickness of the second reflector is 20nm, the doping type is n-type, and the doping concentration is 7 multiplied by 10¹⁷cm^-3；

The first metal electrode is a Ti/Au electrode and sequentially comprises a Ti layer and an Au layer from bottom to top, the thickness of the Ti layer is 50nm, and the thickness of the Au layer is 200 nm;

the second metal electrode is located at the bottom of the step on the fault-tolerant layer and electrically connected with the fault-tolerant layer, and the second metal electrode is the same as the first metal electrode.

Fig. 4 is a schematic diagram illustrating a refractive index of a partial structure in a simulated infrared detector corresponding to an infrared detector in which incident light is incident from a side of the optical resonant cavity away from the substrate according to the above embodiment of the present application, and a schematic diagram illustrating a distribution of a light field of the incident light incident into the simulated infrared detector; the wave-shaped curve is a light field distribution curve, and the square wave is a refractive index distribution curve of each structure in the infrared detector. As can be seen from fig. 4, the infrared detector includes three cascaded steps, and the superlattice absorption structure in each cascaded step is respectively located at antinodes at different positions so as to sufficiently absorb and utilize incident light, the first mirror in the infrared detector includes 10 pairs of stacked AlAsSb layers and GaSb layers, and the refractive index difference between the AlAsSb layers and the GaSb layers is about 0.6, so that the reflectivity of the first mirror is greater than or equal to 90%, and most of light beams incident on the first mirror are reflected back into the optical resonator, thereby improving the utilization rate of light. Thus, the figure demonstrates the effectiveness and feasibility of the infrared detector described above in the present application.

Next, we will describe an infrared detector in which incident light is directly incident from the substrate side as an example:

on the basis of any of the above embodiments, in one embodiment of the present application, the first mirror is a bragg mirror.

It should be noted that, in the embodiment of the present application, the reflectivity of the first mirror is not too high, nor too low, and if the reflectivity of the first mirror is too high, when the incident light that enters the first mirror from the outside enters the first mirror, the first mirror can highly reflect the incident light, so as to reduce the transmittance of the incident light, so that the incident light enters the optical resonant cavity less, and further the utilization rate of the incident light is reduced; if the reflectivity of the first reflector is too low, when the incident light reflected back from the second reflector is reflected to the first reflector, the first reflector can highly transmit the incident light, so that the incidence rate of the incident light is reduced, the incident light is less reflected to the superlattice absorption structure, and the utilization rate of the incident light is reduced. Based on this, in an embodiment of the present application, on the basis of any one of the above embodiments, the reflectance of the first reflecting mirror has a value in a range of 30% to 70%.

As shown in fig. 5, in an embodiment of the present application, if incident light enters from one side of the substrate, the first reflecting mirror includes a plurality of AlAsSb layers and a plurality of GaSb layers, and the plurality of AlAsSb layers included in the first reflecting mirror and the plurality of GaSb layers included in the first reflecting mirror are alternately arranged, where a number of layers of the AlAsSb layers included in the first reflecting mirror ranges from 5 to 7, and a number of layers of the GaSb layers included in the first reflecting mirror ranges from 5 to 7, it should be noted that in the embodiment of the present application, the number of layers of the AlAsSb layers included in the first reflecting mirror 31 is one layer more than the number of layers of GaSb layers included in the first reflecting mirror 31.

In the embodiment of the present application, the value range of the thickness of the AlAsSb layer included in the first reflecting mirror and the value range of the thickness of the GaSb layer included in the first reflecting mirror are not limited, and are determined as the case may be.

It should be noted that the undoped GaSb layer is generally p-type, wherein the undoped GaSb layer generates free carrier absorption and lowers its own refractive index, so the inventors doped the GaSb layer included in the first mirror n-type.

Based on this, in an embodiment of the present application, a doping type of the GaSb layer included in the first reflective mirror is n-type, and a value range of a doping concentration is 1 × 10¹⁶cm^-3-1×10¹⁷cm^-3To neutralize the background hole concentration of the GaSb layer included in the first mirror, thereby eliminating free carrier absorption in the GaSb layer while increasing its own refractive index.

Optionally, in an embodiment of the present application, the chemical formula of AlAsSb in the first mirror is AlAs_0.08Sb_0.92The chemical formula of GaSb in the superlattice fault-tolerant layer is GaSb, in other embodiments of the application, the chemical formula of AlAsSb in the superlattice fault-tolerant layer can be in other forms,

continuing with fig. 5, in an embodiment of the present application, based on any of the above embodiments, the second mirror 32 includes a layer of Ag. In another embodiment of the present application, the second mirror 32 may further include an Au layer, and in other embodiments of the present application, the second mirror 32 may further include other film layers made of other materials, which are not limited in this application, as the case may be.

Optionally, in an embodiment of the present application, a range of the thickness of the second reflector 32 is 200nm to 500nm, and in other embodiments of the present application, a range of the thickness of the second reflector 32 may also be other values, which is not limited in the present application and is determined as the case may be.

On the basis of any one of the above embodiments, in an embodiment of the present application, the reflectivity of the second reflecting mirror is greater than or equal to 90% so as to reflect more incident light incident on the surface of the second reflecting mirror to the superlattice absorption structure, so that the superlattice absorption structure fully absorbs the incident light, thereby further improving the utilization rate of the infrared detector for the incident light, improving the conversion efficiency of the infrared detector, and further improving the detection rate of the infrared detector.

Continuing with fig. 5, on the basis of any of the above embodiments, in an embodiment of the present application, the infrared detector further includes: a second contact layer 110 between the plurality of cascaded steps 40 and the second mirror 32.

In addition to any of the above embodiments, in an embodiment of the present application, the second contact layer is an InAs contact layer, and in other embodiments of the present application, the second contact layer may also be a contact layer of another material, which is not limited in this application, and is determined as the case may be.

On the basis of any of the above embodiments, in an embodiment of the present application, the thickness of the second contact layer ranges from 10nm to 30nm, the doping type of the second contact layer is n-type, and the doping concentration of the second contact layer ranges from 1 × 10¹⁷cm^-3-1×10¹⁹cm^-3。

On the basis of any one of the above embodiments, in an embodiment of the present application, the method further includes: a plurality of third spacer layers 120, the plurality of third spacer layers 120 and the plurality of cascade steps 40 are alternately arranged, and the third spacer layers 120 are located between two adjacent cascade steps 40, so that the cascade steps 40 are located on an antinode of the optical resonant cavity.

It should be noted that in the embodiment of the present application, the third spacer layer is located between adjacent antinodes.

Optionally, in an embodiment of the present application, the third spacer layer is a GaSb layer, which is not limited in the present application, as the case may be.

Optionally, in an embodiment of the present application, the thickness of the third spacer layer is 200nm to 300nm, the doping type of the third spacer layer is p-type, and the doping concentration of the third spacer layer has a value ranging from 1 × 10¹⁶cm^-3-1×10¹⁸cm^-3。

On the basis of the above embodiment, in an embodiment of the present application, the infrared detector further includes: a fourth spacer layer 130, said fourth spacer layer 130 being located on a side of said plurality of cascaded steps 40 facing said substrate 10. It should be noted that, in the embodiment of the present application, the third spacer layer 120 and the fourth spacer layer 130 may be the same or different, and specifically, in an embodiment of the present application, the third spacer layer 120 and the fourth spacer layer 130 are the same. It should be noted that, in the embodiment of the present application, the fourth spacing layer 130 is also located between adjacent antinodes.

It should be noted that, for the infrared detector provided in the present application, where the incident light is directly incident from the side of the substrate away from the optical resonant cavity, on the basis of any of the above embodiments, in an embodiment of the present application, the hole barrier structure may include 6 to 10 second quantum wells, which is not limited in this application, as the case may be.

The following describes, in conjunction with a specific embodiment, an infrared detector provided by the present application, in which incident light is directly incident from one side of the substrate, taking a resonant wavelength of 4 μm as an example:

the infrared detector includes: the device comprises a substrate, a buffer layer, a first reflector, an error-tolerant layer, a fourth spacing layer, a plurality of third spacing layers, 3 cascade steps, a third transition layer, a second contact layer, a second reflector, a first metal electrode and a second metal electrode;

the substrate is a GaSb substrate;

the buffer layer is a GaSb buffer layer, the thickness of the GaSb buffer layer is 500nm, and the GaSb buffer layer is an undoped buffer layer;

the first reflector is a Bragg reflector, and the refractive index of the first reflector is close to 65%;

specifically, the bragg reflector comprises 7 AlAsSb layers and 6 GaSb layers, wherein the 7 AlAsSb layers and the 6 GaSb layers are alternately arranged, and AlAsSb (such as AlAs)_0.08Sb_0.92) The thickness of the layer is 315nm, the AlAsSb (e.g. AlAs)_0.08Sb_0.92) The layer being undoped AlAsSb (e.g. AlAs)_0.08Sb_0.92) The thickness of the GaSb layer is 263nm, the doping type of the GaSb layer is n-type, and the doping concentration is 7 multiplied by 10¹⁶cm^-3；

The fault-tolerant layer comprises a first sub-fault-tolerant layer and a second sub-fault-tolerant layer, the first sub-fault-tolerant layer is a GaSb layer, the thickness of the GaSb layer is 209nm, the surface of the GaSb layer, which is far away from the side of the substrate, is doped, the doping type is p, and the doping concentration is 2 multiplied by 10¹⁷cm^-3；

The second sub-fault-tolerant layer is AlInSb/InAs (such as AlIn)_0.3Sb_0.7InAs) a superlattice fault-tolerant layer;

specifically, the AlIn_0.3Sb_0.7the/InAs superlattice fault-tolerant layer comprises 21 layers of AlIn_0.3Sb_0.7Layer and 21 InAs layers, each layer of AlIn_0.3Sb_0.7The thickness of the layer is 1.9nm, the AlIn_0.3Sb_0.7The layer is undoped AlIn_0.3Sb_0.7Each InAs layer has a thickness of 8.1nm, a doping type of n-type and a doping concentration of 5 × 10¹⁷cm^-3；

The third interlayer and the cascade steps are alternately arranged, and the third interlayer is positioned between two adjacent cascade steps;

specifically, the third interlayer is a GaSb layer with the thickness of 273nm, the doping type is p-type, and the doping concentration is 2.4 multiplied by 10¹⁶cm^-3The third separation layer is positioned between adjacent antinodes;

the fourth spacing layer is positioned on one side of the plurality of cascade steps facing the substrate, the fourth spacing layer and the third spacing layer are the same, and the fourth spacing layer is positioned between adjacent antinodes;

the cascade step comprises an electron barrier structure, a superlattice absorption structure and a hole barrier structure; the electron barrier structure is composed of 4 first quantum wells, and each first quantum well comprises an AlSb layer and a GaSb layer which are stacked;

specifically, the 4 first quantum wells are sequentially a first quantum well, a second first quantum well, a third first quantum well and a fourth first quantum well from bottom to top (namely, along the direction from the substrate to the optical resonant cavity), wherein the first quantum well is composed of a layer with the thickness of 1.2nmAlSb and a layer with the thickness of 7.1nmGaSb, the second first quantum well is composed of a layer with the thickness of 1.2nmAlSb and a layer with the thickness of 6.0nmGaSb, the third first quantum well is composed of a layer with the thickness of 1.3nmAlSb and a layer with the thickness of 4.5nmGaSb, and the fourth first quantum well is composed of a layer with the thickness of 1.3nmAlSb and a layer with the thickness of 3.1 nmGaSb. In the first quantum well, all AlSb layers are undoped AlSb layers, the doping type of each GaSb layer is p-type doping, and the doping concentration is 2.4 multiplied by 10¹⁶cm^-3；

The superlattice absorption structure comprises 40 periods, wherein each period sequentially comprises an InAs layer, an InSb layer, a GaSb layer and an InSb layer;

specifically, the method comprises the following steps: in each period, the thickness of the InAs layer is 2.01nm, the thickness of the InSb layer is 0.13nm, the thickness of the GaSb layer is 2.55nm and the thickness of the InSb layer is 0.13nm, the doping types of the InAs layer, the InSb layer, the GaSb layer and the InSb layer are all p-type, and the doping concentration is 2.4 multiplied by 10¹⁶cm^-3；

The hole barrier structure is composed of 8 second quantum wells, and each second quantum well comprises an AlSb layer and an InAs layer which are stacked; the 8 second quantum wells sequentially comprise a first second quantum well, a second quantum well, a third second quantum well, a fourth second quantum well, a fifth second quantum well, a sixth second quantum well, a seventh second quantum well and an eighth second quantum well from bottom to top;

specifically, the first and second quantum wells are formed of a thick materialThe thickness of the second quantum well is 1.7nmAlSb layer and the thickness of the second quantum well is 3.1nmInAs layer, the thickness of the third second quantum well is 1.7nmAlSb layer and the thickness of the third quantum well is 3.5nmInAs layer, the thickness of the fourth second quantum well is 1.5nmAlSb layer and the thickness of the third quantum well is 3.7nmInAs layer, the thickness of the fifth second quantum well is 1.5nmAlSb layer and the thickness of the fourth quantum well is 4.4nmInAs layer, the thickness of the sixth second quantum well is 1.5nmAlSb layer and the thickness of the fourth quantum well is 5.3nmInAs layer, the thickness of the seventh second quantum well is 1.5 nmInAsSb layer and the thickness of the fourth quantum well is 6.1nmInAs layer, and the thickness of the eighth second quantum well is 1.5 nmInAsSb layer and the thickness of the eighth quantum well is 0.7 nmInAs layer. In the second quantum well, all AlSb layers are undoped AlSb layers, at least one InAs layer is doped, the doping type of at least one InAs layer is n-type doping, and the doping concentration is 1.5 multiplied by 10¹⁷cm^-3；

The second contact layer is an InAs contact layer, the thickness of the second contact layer is 20nm, the doping type is n-type, and the doping concentration is 5 multiplied by 10¹⁷cm^-3；

The second reflector is an Ag layer, the thickness of the second reflector is 200nm, and the reflectivity of the second reflector is close to 95%;

the first metal electrode is an Au electrode, and the thickness of the first metal electrode is 300 nm;

the second metal electrode is located at the bottom of the step on the fault-tolerant layer, and the second metal electrode is the same as the first metal electrode.

Fig. 6 shows a schematic diagram of refractive indexes of a partial structure in a simulated infrared detector corresponding to an infrared detector in which incident light is directly incident from one side of the substrate according to the embodiment of the present application, and a schematic diagram of a light field distribution of the incident light incident into the simulated infrared detector; the wave-shaped curve is a light field distribution curve, and the square wave is a refractive index distribution curve of each structure in the infrared detector. As can be seen from the figure, the infrared detector comprises three cascade steps, the superlattice absorption structure in each cascade step is respectively located at antinodes at different positions so as to sufficiently absorb and utilize incident light, the first reflecting mirror in the infrared detector comprises 6 pairs of stacked AlAsSb layers and GaSb layers, the refractive index difference between the AlAsSb layers and the GaSb layers is about 0.6, the reflectivity of the first reflecting mirror can be enabled to be larger than or equal to 65%, when the incident light reflected from the second reflecting mirror is incident on the first reflecting mirror, the first reflecting mirror reflects most of light beams back to the optical resonant cavity, and the utilization rate of the light is improved. The figure thus illustrates the effectiveness and feasibility of an infrared detector having the structure described above in the present application.

To sum up, among the infrared detector that this application embodiment provided, including a plurality of cascade steps, cascade step includes electron barrier structure, superlattice absorption structure and hole barrier structure, cascade step is located in the optics resonant cavity, when surveying, if incident light gets into this optics resonant cavity, incident light carries out multiple reflection between the first speculum of optics resonant cavity and second mirror to make this incident light can pass through superlattice absorption structure many times, resonance takes place to strengthen superlattice absorption structure to this incident light's absorption, thereby increase substantially this infrared detector's quantum efficiency, and then improve infrared detector's detectivity.

In addition, the infrared detector with the cascade steps is combined with the optical resonant cavity, so that the advantages of high response speed, low dark current level and the like of the interband cascade detector are kept, the quantum efficiency of the interband cascade detector can be obviously improved, and the detector rate of the infrared detector is improved. For example, an infrared detector including an optical resonant cavity and a plurality of cascaded steps in this application can increase room temperature detection by an order of magnitude at a peak corresponding wavelength of 4 μm (i.e., the resonant wavelength). In addition, the optical resonant cavity in the application can provide better wavelength selectivity, so that the infrared detector comprising the optical resonant cavity in the application can be used in combination with a laser with corresponding wavelength, and the application range is wide, for example, the infrared detector can be applied to gas detection and energy transmission, hyperspectral imaging and multispectral imaging and other applications.

It is noted that, in the present application, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

It should be noted that, in the present application, for example, the value range of the numerical value is a-b, and the value range of the numerical value includes both the numerical values from a to b and the end values of a and b.

All parts in the specification are described in a mode of combining parallel and progressive, each part is mainly described to be different from other parts, and the same and similar parts among all parts can be referred to each other.

In the above description of the disclosed embodiments, features described in various embodiments in this specification can be substituted for or combined with each other to enable those skilled in the art to make or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.