Epitaxial structure of infrared detector and preparation method thereof

Abstract

The embodiment of the invention provides an epitaxial structure of an infrared detector and a preparation method thereof, the infrared detector comprises a substrate, and the epitaxial structure comprises a buffer layer, a P-type layer, an i long wave absorption layer, an N-type layer and a cover layer which are sequentially stacked on the substrate from bottom to top; wherein the P type layer comprises an InAs / GaInSb superlattice structure layer; the i long wave absorption layer comprises an InAs / GaInSb superlattice structure layer; and the N-type layer comprises an InAs / GaInSb superlattice structure layer. The epitaxial structure, the i long wave absorption layer, the P-type layer and the N-type layer all comprise the InAs / GaInSb superlattice structure layers, GaInSb ternary components in the superlattice structure layers have the advantages of long carrier life and high absorption coefficient, the performance of the infrared detector is improved, in addition, the InAs / GaInSb superlattice material is thinner in layer thickness reaching a specific cut-off wavelength, and the performance of the infrared detector is improved. And miniaturization of the infrared detector is facilitated.

Description

Technical Field

[0001] The present invention relates to the field of infrared detection technology, and in particular to an epitaxial structure of an infrared detector and a preparation method thereof. Background Art

[0002] After decades of development, infrared detectors have gone through the first generation of scanning imaging, the second generation using focal plane arrays and readout circuits, and the third generation of dual-color focal plane arrays based on the second generation, and now the fourth generation of multi-color fusion large-array focal planes. At present, the development trend of infrared detectors mainly has four directions: high operating temperature, generally requiring short-wave and medium-wave infrared detectors to work at a temperature higher than 180K, while long-wave infrared detectors are required to work at a temperature of 110K; long operating wavelength, the response wavelength of infrared detectors is above 10 microns; wide working band coverage, including dual-color, three-color and other multi-color responses, and a wide response spectrum coverage; large array, the wafer size has exceeded 4 inches, and the focal plane array has to exceed 1k*1k.

[0003] Long-wave infrared detectors have broad application prospects. There are three common long-wave infrared detector materials: mercury cadmium telluride material (MCT), quantum well infrared detector (QWIP) represented by AlGaAs / GaAs system, and III~V antimonide type II superlattice materials. Among these three materials, the substrate of MCT is expensive, and the stability of large-area array growth is poor; QWIP has low quantum efficiency and large dark current. Antimonide type II superlattice materials have four major advantages: the band gap is easy to adjust and the coverage band is wide; the lattice constant is close; the large effective mass of electrons can suppress Auger recombination; large-area uniformity is good, which is conducive to large-area epitaxy.

[0004] The carrier lifetime of InAs / InAsSb materials in antimonide type II superlattice materials is very long, but under the same cutoff wavelength conditions, its layer thickness is very large, and the absorption coefficient is significantly lower than that of InAs / GaSb. In the related art, the long-wave infrared detectors made of antimonide type II superlattice materials fail to take into account the two advantages of long carrier lifetime and high absorption coefficient, which affects the overall performance of the long-wave infrared detectors. Summary of the invention

[0005] In view of this, an embodiment of the present invention provides an epitaxial structure of an infrared detector and a preparation method thereof, which are used to solve the problem that the materials of existing infrared detectors have low absorption coefficients and short carrier lifetimes, resulting in poor performance.

[0006] In a first aspect, an embodiment of the present invention provides an epitaxial structure of an infrared detector, wherein the infrared detector includes a substrate, and the epitaxial structure includes:

[0007] A buffer layer, a P-type layer, an i-long wave absorption layer, an N-type layer and a cap layer are sequentially stacked on the substrate from bottom to top;

[0008] Wherein, the P-type layer includes an InAs / GaInSb superlattice structure layer;

[0009] The i long-wave absorption layer includes an InAs / GaInSb superlattice structure layer;

[0010] The N-type layer includes an InAs / GaInSb superlattice structure layer.

[0011] According to an embodiment of the present invention, the InAs / GaInSb superlattice structure layer includes a GaInSb layer of a first preset thickness and an InAs layer of a second preset thickness;

[0012] The InAs / GaInSb superlattice structure layer further includes a GaAs interface layer, and the GaAs interface layer with a third preset thickness is formed on the InAs layer with the second preset thickness.

[0013] According to an embodiment of the present invention, the doping type of the P-type layer is P-type doping, the dopant includes Be, and the doping concentration is 2×10 18 cm ~3 ~5×10 18 cm ~3 .

[0014] According to an embodiment of the present invention, the doping type of the i long-wave absorption layer is P-type doping, the dopant includes Be, and the doping concentration is 1×10 16 cm ~3 ~5×10 16 cm ~3 .

[0015] According to an embodiment of the present invention, the doping type of the N-type layer is N-type doping, the dopant includes Si, and the doping concentration is 2×10 18 cm ~3 ~5×10 18 cm ~3 .

[0016] In a second aspect, an embodiment of the present invention provides a method for preparing an epitaxial structure of an infrared detector, comprising:

[0017] epitaxially growing a buffer layer on the substrate;

[0018] epitaxially growing a P-type layer on the buffer layer;

[0019] epitaxially growing an i long-wave absorption layer on the P-type layer;

[0020] epitaxially growing an N-type layer on the i long-wave absorption layer;

[0021] epitaxially growing a cap layer on the N-type layer;

[0022] Wherein, the P-type layer includes an InAs / GaInSb superlattice structure layer, the i-long wave absorption layer includes an InAs / GaInSb superlattice structure layer, and the N-type layer includes an InAs / GaInSb superlattice structure layer.

[0023] According to an embodiment of the present invention, the step of epitaxially growing a P-type layer on the buffer layer includes:

[0024] Alternatingly growing GaInSb layers of a first preset thickness and InAs layers of a second preset thickness;

[0025] Wherein, a GaAs interface layer of a third preset thickness is grown on the InAs layer of a second preset thickness;

[0026] The number of cycles is 50~80.

[0027] According to an embodiment of the present invention, the step of epitaxially growing an i long-wave absorption layer on the P-type layer comprises:

[0028] Alternatingly growing GaInSb layers of a first preset thickness and InAs layers of a second preset thickness;

[0029] Wherein, a GaAs interface layer of a third preset thickness is grown on the InAs layer of a second preset thickness;

[0030] The number of cycles is 100~200.

[0031] According to an embodiment of the present invention, P-type doping is performed when growing the GaInSb layer of the first preset thickness, and the dopant includes Be.

[0032] According to an embodiment of the present invention, the step of epitaxially growing an N-type layer on the i long-wave absorption layer comprises:

[0033] Alternatingly growing GaInSb layers of a first preset thickness and InAs layers of a second preset thickness;

[0034] Wherein, a GaAs interface layer of a third preset thickness is grown on the InAs layer of a second preset thickness;

[0035] The number of cycles is 50~80;

[0036] N-type doping is performed when growing the InAs layer of the second preset thickness, and the dopant includes Si.

[0037] The epitaxial structure of the infrared detector and the preparation method thereof provided by the embodiments of the present invention can at least achieve the following technical effects: the i long-wave absorption layer, the P-type layer and the N-type layer all include an InAs / GaInSb superlattice structure layer, and the GaInSb ternary component in the superlattice structure layer has the advantages of a long carrier lifetime and a high absorption coefficient, which is beneficial to improving the performance of the infrared detector. In addition, the layer thickness of the InAs / GaInSb superlattice material to reach a specific cut-off wavelength is thinner, which is beneficial to the miniaturization of the infrared detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0039] Figure 1 A schematic diagram of the structure of the epitaxial structure of an infrared detector according to an embodiment of the present invention is schematically shown;

[0040] Figure 2 A flow chart schematically shows a method for preparing an epitaxial structure of an infrared detector according to an embodiment of the present invention;

[0041] Reference numerals:

[0042] 10: substrate; 20: buffer layer; 30: P-type layer; 40: i-long wave absorption layer; 50: N-type layer; 60: cap layer. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0045] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0046] In the prior art, the materials of long-wave infrared detectors include antimonide type II superlattice materials. The carrier lifetime of InAs / InAsSb material in antimonide type II superlattice materials is very long, but its layer thickness is very large under the same cut-off wavelength conditions, and the absorption coefficient is significantly reduced compared to InAs / GaSb. The carrier lifetime of InAs / GaInSb material is greater than that of InAs / GaSb. Although it is not as good as InAs / InAsSb, its absorption coefficient is greater than that of InAs / InAsSb and InAs / GaSb. Therefore, InAs / GaInSb material has unique advantages and can take into account the two advantages of longer carrier lifetime and high absorption coefficient; at the same time, the layer thickness of InAs / GaInSb material to reach a specific cut-off wavelength is thinner. An embodiment of the present invention provides an epitaxial structure of an infrared detector, and the material of the epitaxial structure includes InAs / GaInSb material.

[0047] Combine the following Figure 1 The epitaxial structure of the infrared detector according to the embodiment of the present invention is described.

[0048] like Figure 1 As shown, the epitaxial structure of the infrared detector provided by the embodiment of the present invention includes a buffer layer 20, a P-type layer 30, an i-long wave absorption layer 40, an N-type layer 50 and a cap layer 60 stacked sequentially from bottom to top on a substrate 10. Among them, the P-type layer includes an InAs / GaInSb superlattice structure layer; the i-long wave absorption layer includes an InAs / GaInSb superlattice structure layer; and the N-type layer includes an InAs / GaInSb superlattice structure layer.

[0049] Specifically, an epitaxial structure is epitaxially grown on a substrate, and the epitaxial structure includes a buffer layer 20, a P-type layer 30, an i-long wave absorption layer 40, an N-type layer 50, and a cap layer 60. The P-type layer 30, the i-long wave absorption layer 40, and the N-type layer 50 all include an InAs / GaInSb superlattice structure layer, and the InAs / GaInSb superlattice structure layer includes a periodic alternating growth of GaInSb layers and InAs layers. The materials, structures, etc. of each layer are described in detail below.

[0050] The material of the substrate 10 includes sapphire, silicon carbide, aluminum nitride, gallium oxide, silicon, etc. The substrate 10 of the present invention includes a GaSb substrate. The material of the buffer layer 20 includes GaSb, etc. For example, the buffer layer 20 is a GaSb buffer layer. The doping type of the GaSb buffer layer is P-type doping, and the dopant includes Be, and the doping concentration can be 2×10 18 cm ~3 The material of the cap layer 60 includes InAs, for example, the cap layer 60 is an InAs cap layer. The doping type of the InAs cap layer is N-type doping, the dopant includes Si, and the doping concentration can be 2×10 18 cm ~3 .

[0051] The i long-wave absorption layer 40 includes an InAs / GaInSb superlattice structure layer formed by a period of alternately grown GaInSb layers and InAs layers, and the number of periods is 100 to 200 times. The material of the superlattice structure layer includes a binary component InAs material and a ternary component GaInSb material. The GaInSb material in the superlattice structure layer has the advantages of a longer carrier lifetime and a high absorption coefficient, which is beneficial to improving the performance of the device. In addition, the thickness of the InAs / GaInSb superlattice structure layer to reach a specific cutoff wavelength is thinner, which is beneficial to reducing the volume of the device.

[0052] The composition of In in GaInSb is 0.21~0.28. For example, the composition of In is 0.25, the composition of Ga is 0.75, and GaInSb is Ga 0.75 In 0.25 Sb, thus the InAs / GaInSb superlattice structure layer is InAs / Ga 0.75 In 0.25 Sb superlattice structure layer. InAs / Ga 0.75 In 0.25 The Sb superlattice structure layer includes a first preset thickness of Ga 0.75 In 0.25 Sb layer and a second preset thickness InAs layer, for example, the first preset thickness is 7ML, the second preset thickness is 10ML, ML is the atomic layer thickness, so InAs / Ga 0.75 In 0.25 The Sb superlattice structure layer can be 10MLInAs / 7MLGa 0.75 In 0.25 Sb superlattice structure layer. 10MLInAs / 7MLGa 0.75 In 0.25 Ga in Sb superlattice structure layer 0.75 In 0.25 Compared with the GaSb binary component, the Sb ternary component uses part of the In component to replace the Ga component to form the GaSb binary component. 0.75In 0.25 The Sb component can reduce the problem of low minority carrier lifetime caused by Ga defects, increase the lifetime of minority carriers, thereby reducing the dark current of the long-wave infrared detector and increasing its quantum efficiency, thereby improving the performance of the long-wave infrared detector.

[0053] Furthermore, the P-type layer 30 and the N-type layer 50 are also InAs / GaInSb superlattice structure layers, and the superlattice structure layer can be 10MLInAs / 7MLGa 0.75 In 0.25 The P-type layer 30 includes an InAs / GaInSb superlattice structure layer formed by periodic alternating growth of GaInSb layers and InAs layers, and the number of periods is 50 to 80. The N-type layer 50 includes an InAs / GaInSb superlattice structure layer formed by periodic alternating growth of GaInSb layers and InAs layers, and the number of periods is 50 to 80.

[0054] In an embodiment of the present invention, the i long-wave absorption layer 40, the P-type layer 30 and the N-type layer 50 all include an InAs / GaInSb superlattice structure layer. The GaInSb ternary component in the superlattice structure layer has the advantages of a long carrier lifetime and a high absorption coefficient, which is beneficial to improving the performance of the infrared detector. In addition, the InAs / GaInSb superlattice material has a thinner layer thickness to reach a specific cut-off wavelength, which is beneficial to the miniaturization of the infrared detector.

[0055] In an optional embodiment, the InAs / GaInSb superlattice structure layer includes a GaInSb layer of a first preset thickness and an InAs layer of a second preset thickness; the InAs / GaInSb superlattice structure layer also includes a GaAs interface layer, and the GaAs interface layer of a third preset thickness is formed on the InAs layer of the second preset thickness.

[0056] Specifically, during the epitaxial growth of the InAs / GaInSb superlattice structure layer, a GaInSb layer of a first preset thickness and an InAs layer of a second preset thickness are alternately grown. 0.75 In 0.25 The number of cycles of the alternating growth of the P-type layer 30 , the i-long wave absorption layer 40 and the N-type layer 50 is different.

[0057] For example, in the P-type layer 30, 10MLInAs layer and 7MLGa 0.75 In 0.25 The number of periods of the Sb layer is 50 to 80 times; in the i long-wave absorption layer 40, the 10MLInAs layer and the 7MLGa 0.75 In 0.25The number of cycles of the Sb layer is 100~200 times; in the N-type layer 50, the 10MLInAs layer and the 7MLGa 0.75 In 0.25 The number of periods of the Sb layer is 50 to 80. In a specific embodiment, the number of periods in the P-type layer 30 is 50; the number of periods in the i-long wave absorption layer 40 is 100; and the number of periods in the N-type layer 50 is 50.

[0058] In the growth of 10MLInAs / 7MLGa 0.75 In 0.25 In the process of growing the Sb superlattice structure layer, in each growth cycle, after growing 10MLInAs, a GaAs interface layer of a third preset thickness is grown. For example, after growing 10MLInAs, a 0.5MLGaAs interface layer is grown. The 0.5ML GaAs interface layer can make the epitaxial wafer lattice constant more compatible with the GaSb substrate, which is beneficial to improving the quality of the material.

[0059] After growing the 10MLInAs layer, continue to grow the 0.5ML GaAs interface layer. 0.75 In 0.25 The GaAs interface layer is introduced into the Sb superlattice structure layer. The lattice constant of GaAs is 5.65325Å, the lattice constant of GaSb substrate is 6.0959Å, the lattice constant of InAs is 6.0583Å, and the lattice constant of Ga 0.75 In 0.25 The lattice constant of Sb is 6.1914Å. Without the introduction of GaAs interface layer, theoretically 10MLInAs / 7MLGa 0.75 In 0.25 The mismatch between Sb and GaSb substrate is 0.282%, and in each 10MLInAs / 7MLGa 0.75 In 0.25 The theoretical mismatch of inserting 0.5ML GaAs interface layer into Sb period is 0.067%. Therefore, the introduction of GaAs interface layer can reduce 10MLInAs / 7MLGa 0.75 In 0.25 The Sb superlattice does not match the lattice of the GaSb substrate, thereby improving the quality of the material grown.

[0060] In addition, the introduction of GaAs interface layer also provides a new way to adjust 10MLInAs / 7MLGa 0.75 In 0.25 The freedom of the Sb superlattice material band, its thickness and the position of insertion in the superlattice structure will lead to the difference between 10MLInAs / 7MLGa 0.75 In 0.25The energy bands of Sb superlattice produce different changes, so the energy bands of materials can be regulated more flexibly.

[0061] In the embodiment of the present invention, by 10MLInAs / 7MLGa 0.75 In 0.25 The GaAs interface layer is introduced into the Sb superlattice structure layer. On the one hand, the lattice constant of GaAs is 5.65325Å, which can reduce 10MLInAs / 7MLGa 0.75 In 0.25 The Sb superlattice does not match the lattice of the GaSb substrate, thereby improving the quality of material growth; on the other hand, the introduction of the GaAs interface layer also provides a new way to adjust the 10MLInAs / 7MLGa 0.75 In 0.25 The freedom of the energy band of Sb superlattice materials can more flexibly control the energy band of the material.

[0062] In an optional embodiment, the doping type of the P-type layer 30 is P-type doping, and the doping concentration is 2×10 18 cm ~3 ~5×10 18 cm ~3 The doping type of the long-wave absorption layer 40 is P-type doping, and the doping concentration is 1×10 16 cm ~3 ~5×10 16 cm ~3 The doping type of the N-type layer 50 is N-type doping, and the doping concentration is 2×10 18 cm ~3 ~5×10 18 cm ~3 .

[0063] Specifically, for the P-type layer 30, when growing Ga 0.75 In 0.25 The Sb layer is doped with P-type, and the dopant includes Be, with a doping concentration of 2×10 18 cm ~3 ~5×10 18 cm ~3 For the i long-wave absorption layer 40, when growing Ga 0.75 In 0.25 The Sb layer is doped with P-type, and the dopant includes Be, with a doping concentration of 1×10 16 cm ~3 ~5×10 16 cm ~3 For the N-type layer 50, N-type doping is performed during the growth of the InAs layer, and the dopant includes Si with a doping concentration of 2×10 18 cm ~3~5×10 18 cm ~3 .

[0064] In summary, in the infrared detector having the above epitaxial structure, the P-type layer 30, the i-long wave absorption layer 40 and the N-type layer 50 include 10MLInAs / 7MLGa 0.75 In 0.25 The Sb superlattice structure layer can reduce the problem of low minority carrier lifetime caused by Ga defects, increase the lifetime of minority carriers, thereby reducing the dark current of the long-wave infrared detector and increasing its quantum efficiency, thereby increasing the detection rate of the long-wave infrared detector and further improving the overall performance of the infrared detector.

[0065] like Figure 2 As shown, an embodiment of the present invention further provides a method for preparing an epitaxial structure of an infrared detector, the preparation method comprising:

[0066] Step 101: epitaxially growing a buffer layer 20 on a substrate 10;

[0067] Step 102: epitaxially growing a P-type layer 30 on the buffer layer 20;

[0068] Step 103: epitaxially growing an i long-wave absorption layer 40 on the P-type layer 30;

[0069] Step 104: epitaxially growing an N-type layer 50 on the i long-wave absorption layer 40;

[0070] Step 105: epitaxially growing a cap layer 60 on the N-type layer 50;

[0071] The P-type layer 30 includes an InAs / GaInSb superlattice structure layer, the i-long wave absorption layer 40 includes an InAs / GaInSb superlattice structure layer, and the N-type layer 50 includes an InAs / GaInSb superlattice structure layer.

[0072] Epitaxial Structure As described above, the epitaxial structure includes a buffer layer 20 , a P-type layer 30 , an i-long wave absorption layer 40 , an N-type layer 50 and a cap layer 60 epitaxially grown on a substrate 10 .

[0073] Molecular beam epitaxy equipment is used for epitaxial growth, with high-purity gallium and high-purity indium as Ga source and In source respectively, high-purity arsenic and high-purity antimony as As source and Sb source respectively, and high-purity beryllium and high-purity silicon as P-type dopant and N-type dopant respectively. The molecular beam epitaxy equipment includes multiple shutters, namely Sb shutter, Ga shutter, In shutter, As shutter, Be shutter and Si shutter.

[0074] The following is a detailed description of the preparation method of the epitaxial structure using a specific embodiment. The substrate 10 is a GaSb substrate. The buffer layer 20 is a GaSb buffer layer, and the doping type of the GaSb buffer layer is P-type doping, and the dopant includes Be. The P-type layer 30 is 10MLInAs / 7MLGa 0.75 In 0.25 Sb superlattice structure layer, the doping type of the P-type layer 30 is P-type doping, and the dopant includes Be. i The long-wave absorption layer 40 is 10MLInAs / 7MLGa 0.75 In 0.25 Sb superlattice structure layer, the doping type of the i long wave absorption layer 40 is P type doping, and the dopant includes Be.

[0075] N-type layer 50 is 10MLInAs / 7MLGa 0.75 In 0.25 Sb superlattice structure layer, the doping type of the N-type layer 50 is N-type doping, and the dopant includes Si. The cap layer 60 is an InAs cap layer, and the doping type of the InAs cap layer is N-type doping, and the dopant includes Si.

[0076] The preparation process of the epitaxial structure is as follows.

[0077] First, the GaSb substrate is heated to 380°C, and then the Sb shutter is opened to introduce an appropriate amount of Sb to protect the GaSb substrate.

[0078] The temperature of the GaSb substrate was further raised to 690° C. in the Sb atmosphere and maintained at this temperature for 20 minutes to remove the residual gas components in the substrate.

[0079] After the gas removal was completed, the temperature of the GaSb substrate was lowered to 610 °C, and then the Ga shutter and Be shutter were opened to grow the Be-doped GaSb buffer layer. The growth time was 5 min, and the Be doping concentration was 2 × 10 18 cm ~3 .

[0080] After the growth of the GaSb buffer layer is completed, the Ga shutter and the Be shutter are closed, the GaSb substrate temperature is slowly reduced, and the surface reconstruction of the material is observed using a reflection high-energy electron diffractometer. When the diffraction image is observed to change from X3 reconstruction to X5 reconstruction, the temperature is recorded and represented by Tc.

[0081] After recording Tc, the reflection high-energy electron diffractometer was turned off and the temperature of the GaSb substrate was raised to (Tc+110)°C. After reaching (Tc+110)°C, the Ga shutter and Be shutter were opened again to continue growing a 500-nanometer GaSb buffer layer with a Be doping concentration of 2×10 18 cm ~3 .

[0082] After the growth of the GaSb buffer layer is completed, the Ga shutter and Be shutter are closed, and the GaSb substrate temperature is lowered to Tc, and the growth of the 10MLInAs / 7MLGa P-type layer 30 is started. 0.75 In 0.25 Sb superlattice structure layer. Growth of 7MLGa 0.75 In 0.25 The Sb layer was doped with Be at a concentration of 3×10 18 cm ~3 .

[0083] Take the Ga growth rate of 0.5 ML / s and the In growth rate of 0.167 ML / s as an example. First, open the Ga shutter, In shutter, Sb shutter and Be shutter for 10.5 seconds at the same time to grow 7 MLGa. 0.75 In 0.25 Sb layer. Then close the Ga shutter, In shutter, Sb shutter and Be shutter, open the As shutter for 4 seconds, then open the In shutter, keep the In shutter and As shutter open for 60 seconds to grow 10MLInAs. Then close the In shutter alone, keep the As shutter for 4 seconds, then close the As shutter, and open the Ga shutter for 1 second, so that Ga grows 0.5ML GaAs interface layer in As atmosphere. After completing a cycle of growth, return to the first step to grow 7MLGa 0.75 In 0.25 Sb layer.

[0084] After 50 cycles of growth of the P-type layer 30 are completed, 100 cycles of the i-long wave absorption layer 40 are grown at the Tc temperature. 0.75 In 0.25 The Sb layer was doped with Be at a concentration of 2×10 16 cm ~3 .

[0085] Take the Ga growth rate of 0.5 ML / s and the In growth rate of 0.167 ML / s as an example. First, open the Ga shutter, In shutter, Sb shutter and Be shutter for 10.5 seconds at the same time to grow 7 MLGa. 0.75 In 0.25 Sb layer. Then close the Ga shutter, In shutter, Sb shutter and Be shutter, open the As shutter for 4 seconds, then open the In shutter, keep the In shutter and As shutter open for 60 seconds to grow 10MLInAs. Then close the In shutter alone, keep the As shutter for 4 seconds, then close the As shutter, and open the Ga shutter for 1 second, so that Ga grows 0.5ML GaAs interface layer in As atmosphere. After completing a cycle of growth, return to the first step to grow 7MLGa 0.75 In 0.25Sb layer.

[0086] After 100 cycles of growth of the i long-wave absorption layer 40 are completed, 50 cycles of the N-type layer 50 are grown at the Tc temperature. Si doping is performed during the growth of the 10MLInAs layer, with a doping concentration of 2×10 18 cm ~3 .

[0087] Take the Ga growth rate of 0.5ML / s and the In growth rate of 0.167ML / s as an example. First, open the Ga shutter, In shutter, and Sb shutter at the same time to grow 7MLGa 0.75 In 0.25 Sb layer. Then close the Ga shutter, In shutter and Sb shutter, open the As shutter for 4 seconds, then open the In shutter and Si shutter, keep the In shutter, As shutter and Si shutter open for 60 seconds to grow 10MLInAs. Then close the In shutter and Si shutter, maintain the As shutter for 4 seconds, then close the As shutter, and open the Ga shutter for 1 second, so that Ga grows a 0.5ML GaAs interface layer in the As atmosphere. After completing a cycle of growth, return to the first step to grow 7MLGa 0.75 In 0.25 Sb layer.

[0088] After 50 cycles of growing the N-type layer 50, the In shutter, As shutter, and Si shutter are kept open at the Tc temperature to grow a 20 nm N-type InAs cap layer 60 with a doping concentration of 2×10 18 cm ~3 .

[0089] The temperature, growth rate and beam ratio of group V elements to group III elements in the above preparation method are not limited, and the optimal value is selected during the growth process.

[0090] After the epitaxial growth is completed, the epitaxial wafer is made into a single chip through processing techniques such as cleaning, photolithography, dry etching, wet etching, deposition, and magnetron sputtering.

[0091] By epitaxially growing the ternary Ga 0.75 In 0.25 Sb layer, so that the i long-wave absorption layer 40 forms InAs / Ga 0.75 In 0.25 The Sb superlattice structure layer can reduce the impact of the low minority carrier lifetime caused by Ga defects, thereby reducing the dark current of the long-wave infrared detector of the new material component and improving its quantum efficiency, ultimately improving the detection rate of the infrared detector. 0.75 In 0.25The introduction of GaAs interface layer into the Sb ternary component improves the growth quality of the epitaxial structure. At the same time, the introduction of GaAs interface layer also provides a new way to adjust 10MLInAs / 7MLGa 0.75 In 0.25 The freedom of the energy band of Sb superlattice materials can more flexibly control the energy band of the material.

[0092] The epitaxial structure is prepared by the above preparation method, and an infrared detector having the above epitaxial structure is further prepared, wherein the long-wave absorption layer 40, the P-type layer 30 and the N-type layer 50 all include InAs / Ga 0.75 In 0.25 Sb superlattice structure layer, the GaInSb ternary component in the superlattice structure layer has the advantages of long carrier lifetime and high absorption coefficient, which is beneficial to improving the performance of infrared detectors. In addition, the layer thickness of InAs / GaInSb superlattice material to achieve a specific cut-off wavelength is thinner, which is beneficial to the miniaturization of infrared detectors.

[0093] The above is only a specific embodiment of the present invention, but the protection scope of this application is not limited thereto. Any changes or substitutions made within the spirit and principle of the present invention should be included in the protection scope of this application. Therefore, the protection scope of this application should be based on the protection scope of the claims.

Claims

1. An epitaxial structure of an infrared detector, the infrared detector comprising a substrate, characterized in that: The epitaxial structure comprises: A buffer layer, a P-type layer, an i-long-wave absorption layer, an N-type layer and a cap layer are sequentially stacked on the substrate from bottom to top; Wherein, the P-type layer includes an InAs / GaInSb superlattice structure layer; The i long-wave absorption layer includes an InAs / GaInSb superlattice structure layer; The N-type layer includes an InAs / GaInSb superlattice structure layer.

2. The epitaxial structure of the infrared detector according to claim 1, characterized in that: The InAs / GaInSb superlattice structure layer includes a GaInSb layer of a first preset thickness and an InAs layer of a second preset thickness; The InAs / GaInSb superlattice structure layer further includes a GaAs interface layer, and the GaAs interface layer with a third preset thickness is formed on the InAs layer with the second preset thickness.

3. The epitaxial structure of the infrared detector according to claim 1, characterized in that: The doping type of the P-type layer is P-type doping, and the dopant includes Be, and the doping concentration is 2×10 18 cm ~3 ~5×10 18 cm ~3 .

4. The epitaxial structure of the infrared detector according to claim 1, characterized in that: The doping type of the i long-wave absorption layer is P-type doping, and the dopant includes Be, and the doping concentration is 1×10 16 cm ~3 ~5×10 16 cm ~3 .

5. The epitaxial structure of the infrared detector according to claim 1, characterized in that: The doping type of the N-type layer is N-type doping, the dopant includes Si, and the doping concentration is 2×10 18 cm ~3 ~5×10 18 cm ~3 .

6. A method for preparing an epitaxial structure of an infrared detector, characterized in that: The preparation method comprises: epitaxially growing a buffer layer on the substrate; epitaxially growing a P-type layer on the buffer layer; epitaxially growing an i long-wave absorption layer on the P-type layer; epitaxially growing an N-type layer on the i long-wave absorption layer; epitaxially growing a cap layer on the N-type layer; Wherein, the P-type layer includes an InAs / GaInSb superlattice structure layer, the i-long wave absorption layer includes an InAs / GaInSb superlattice structure layer, and the N-type layer includes an InAs / GaInSb superlattice structure layer.

7. The preparation method according to claim 6, characterized in that: The step of epitaxially growing a P-type layer on the buffer layer comprises: Alternatingly growing GaInSb layers of a first preset thickness and InAs layers of a second preset thickness; Wherein, a GaAs interface layer of a third preset thickness is grown on the InAs layer of a second preset thickness; The number of cycles is 50~80.

8. The preparation method according to claim 6, characterized in that: The step of epitaxially growing an i long-wave absorption layer on the P-type layer comprises: Alternatingly growing GaInSb layers of a first preset thickness and InAs layers of a second preset thickness; Wherein, a GaAs interface layer of a third preset thickness is grown on the InAs layer of a second preset thickness; The number of cycles is 100~200.

9. The preparation method according to claim 7 or 8, characterized in that: When growing the GaInSb layer of the first preset thickness, P-type doping is performed, and the dopant includes Be.

10. The preparation method according to claim 6, characterized in that: The step of epitaxially growing an N-type layer on the i long-wave absorption layer comprises: Alternatingly growing GaInSb layers of a first preset thickness and InAs layers of a second preset thickness; Wherein, a GaAs interface layer of a third preset thickness is grown on the InAs layer of a second preset thickness; The number of cycles is 50~80; N-type doping is performed when growing the InAs layer of the second preset thickness, and the dopant includes Si.

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