A double-transition layer mercury cadmium telluride multilayer heterojunction device and its preparation method

Abstract

The invention discloses a double-transition layer HgCdTe multilayer heterojunction device and a preparation method thereof, comprising a CdZnTe substrate and HgCdTe deposited on the CdZnTe substrate. 1‑x Cd x Te epitaxial structure, starting from the CdZnTe substrate: heavily doped wide bandgap n-type Hg 1‑x1 Cd x1 Te contact layer N + , lightly doped n-type Hg 1‑ x2 Cd x2 Te composition gradient transition layer G ‑ , lightly doped n-type Hg 1‑ x3 Cd x3 Te composition gradient transition layer G + , narrow bandgap lightly doped n-type Hg 1‑x4 Cd x4 Te absorption layer ν, lightly doped n-type Hg 1‑ x5 Cd x5 Te composition gradient transition layer G ‑ , lightly doped n-type Hg 1‑ x6 Cd x6 Te composition gradient transition layer G + , heavily doped with wide-bandgap p-type Hg 1‑7 Cd x7 Te contact layer P + The present invention can improve quantum efficiency, suppress thermally excited intrinsic carriers in the absorption layer at high operating temperatures, reduce the Auger recombination process, thereby effectively reducing the dark current of the device and increasing the operating temperature of the device.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor materials and devices, and relates to a double-transition layer mercury cadmium telluride multilayer heterojunction device and a preparation method thereof, specifically a double-transition layer P + G + G - νG + G - N + Mercury cadmium telluride multilayer heterojunction device and preparation method thereof. Background Art

[0002] Mercury cadmium telluride (HgCdTe) materials possess exceptional infrared photoelectric properties and have long held a leading position in the field of high-performance photon-based infrared detector technology. Currently, research institutions worldwide are working to raise the operating temperature of HgCdTe-based infrared focal plane detectors to room temperature to meet the system requirements for small size, light weight, low power consumption, high reliability, and environmental adaptability. Maintaining high detection performance at near-room temperature is a primary challenge in the field of high-operation-temperature (HOT) infrared detection.

[0003] In order to increase the operating temperature of HgCdTe detectors and effectively suppress dark current at high temperatures, the international community has developed a series of technical approaches to optimize Hg vacancies, such as n-on-p, non-intrinsic doping n-on-p, non-intrinsic doping p-on-n, and nBn barrier type, to increase the operating temperature. + / (ν) / N + The device is reverse biased by ν / N + The repulsive effect of the exclusion junction combined with P + / ν extraction junction (Extraction junction) extraction effect to suppress the high concentration of intrinsic carriers in the absorption layer at high operating temperature, thereby suppressing the Auger process to reduce the dark current of the device, so that the device can operate at a higher operating temperature. The non-equilibrium mode HgCdTe structure contains multiple layers of HgCdTe thin films and different doping concentrations and doping types, generally prepared by molecular beam epitaxy (MBE). The n-type layer is generally doped with in-situ In, and the planar junction P-type layer is generally achieved by As ion implantation combined with high-temperature annealing. As ion activation requires heat treatment in an environment with a temperature above 400°C. At high temperatures, the multilayer heterojunction HgCdTe undergoes mutual diffusion of components due to different element ratios, resulting in an increase in the Cd component at the edge of the absorption region and a shortening of the absorption region length, which seriously affects the quantum efficiency of the device. Summary of the Invention

[0004] Based on the above problems, the purpose of the present invention is to provide a double transition layer P + G + G - νG + G - N + Mercury cadmium telluride multilayer heterojunction device and its preparation method, the structure is the same as conventional P + νN + Compared with the structure, a double-layer transition layer is added between the three-layer heterojunction, in which the transition layer G - Components from high to low, transition layer G + The composition changes from low to high, thus forming a low-lying area between the two transition layers. This low-lying area can effectively reduce the increase in the Cd composition at the edge of the absorption layer and the shortening of the effective thickness caused by the mutual diffusion of components due to the activation of high-temperature As ions, thereby improving the quantum efficiency. 1-x4 Cd x4 Te is also added with a certain composition gradient, which forms a built-in electric field that can effectively reduce interface recombination and enhance the collection efficiency of photogenerated carriers in the pn junction. After the device is annealed into a junction, the N + -ν repulsive junction and ν-P + Extraction junction, the absorption layer uses low concentration (N D ≤1×10 14 cm -3 ) N-type doping, which can suppress the thermally excited intrinsic carriers in the absorption layer at high operating temperature, reduce the Auger recombination process and effectively reduce the dark current of the device. + and P + The layer is almost fully transparent to the response spectrum, which has a self-passivation effect and effectively reduces the surface dark current. The end point of the pn junction depletion region is at the wide bandgap layer, which can effectively suppress the tunneling current and increase the operating temperature of the device.

[0005] The objectives of the present invention are mainly achieved through the following technical solutions:

[0006] A double transition layer P + G + G - νG + G - N + HgCdTe multilayer heterojunction devices include CdZnTe (Cd 1-y Zn y Te, CZT) substrate and HgCdTe (Hg 1-x Cd x Te, MCT) epitaxial structure, the epitaxial structure starting from the cadmium zinc telluride substrate is: heavily doped wide band gap n-type Hg1-x1 Cd x1 Te contact layer (N + layer), lightly doped n-type Hg 1-x2 Cd x2 The gradient transition layer (G - layer), lightly doped n-type Hg 1-x3 Cd x3 The gradient transition layer with low to high Te composition (G + layer), narrow bandgap lightly doped n-type Hg 1-x4 Cd x4 Te absorption layer (ν layer), lightly doped n-type Hg 1-x5 Cd x5 The gradient transition layer (G - layer), lightly doped n-type Hg 1-x6 Cd x6 The gradient transition layer with low to high Te composition (G + layer), heavily doped with wide-bandgap p-type Hg 1-7 Cd x7 Te contact layer (P + layer).

[0007] Furthermore, in the above device, the CZT substrate is a (211) B-plane CZT substrate.

[0008] Furthermore, in the above device, the relatively wide bandgap heavily doped n-type Hg 1-x1 Cd x1 The thickness of the Te contact layer is 2 μm, and the material is In-doped HgCdTe material with a doping concentration of (1 to 5)×10 16 cm -3 The Cd component is adjusted according to the component of the absorption layer, and is generally 0.1-0.15 larger than the component of the absorption layer. Taking the medium-wave device as an example, the component x1 in the present invention is 0.45.

[0009] Furthermore, in the above device, the lightly doped Hg 1-x2 Cd x2 The thickness of the Te composition gradient transition layer is 0.3 μm. The material is In-doped n-type HgCdTe material with a doping concentration of N D ≤1×10 14 cm -3 .Hg 1-x2 Cd x2 The composition x2 in the Te composition gradient transition layer changes from Hg 1-x1 Cd x1 The high composition of the Te contact layer is gradually reduced to Hg 1-x3 Cd x3The low component initially used in the Te transition layer is adjusted according to specific needs. In the present invention, the gradient change of the component x2 is specifically used to gradually decrease from 0.45 to 0.2, taking the medium-wave device as an example.

[0010] Furthermore, in the above device, the lightly doped Hg 1-x3 Cd x3 The thickness of the Te composition gradient transition layer is 0.3 μm. The material is In-doped N-type HgCdTe material with a doping concentration of N D ≤1×10 14 cm -3 , Hg 1-x3 Cd x3 The composition x3 in the Te composition gradient transition layer changes from N-type Hg 1-x2 Cd x2 The low composition used at the end of the Te transition layer gradually increases to Hg 1-x4 Cd x4 The components used in the Te absorption layer are adjusted according to specific needs. In the present invention, the gradient change of component x3 is specifically increased from 0.2 to 0.3, taking the medium-wave device as an example.

[0011] Furthermore, in the above detector, the narrow bandgap lightly doped n-type Hg 1-x4 Cd x4 The thickness of the Te absorption layer is 4 μm. 1-x4 Cd x4 The Te absorption layer uses In-doped HgCdTe material with a doping concentration of N D ≤1×10 14 cm -3 A certain component gradient is added to the absorption layer, and the components can be adjusted according to specific needs. In the present invention, the component x4 is specifically reduced from 0.3 to 0.295 using a medium-wave device as an example.

[0012] Furthermore, in the above detector, the lightly doped n-type Hg 1-x5 Cd x5 The thickness of the Te composition gradient transition layer is 0.3 μm. The material is In-doped HgCdTe material, and the doping concentration is reduced to N D ≤1×10 14 cm -3 .Hg 1-x5 Cd x5 The composition x5 in the Te composition gradient transition layer changes from Hg 1-x4 Cd x4 The composition of the Te absorption layer gradually decreases to Hg 1-x6 Cd x6The components initially used in the Te transition layer are adjusted according to specific needs. In the present invention, the gradient change of the component x5 is specifically that the medium-wave device gradually decreases from 0.295 to 0.2.

[0013] Furthermore, in the above detector, the lightly doped n-type Hg 1-x6 Cd x6 The thickness of the Te composition gradient transition layer is 0.3 μm. The material is In-doped HgCdTe material, and the doping concentration is reduced to N D ≤1×10 14 cm -3 .Hg 1-x6 Cd x6 The composition x6 in the Te composition gradient transition layer changes from Hg 1-x5 Cd x5 The low composition used at the end of the Te transition layer gradually increases to Hg 1-x7 Cd x7 The components used in the Te contact layer are adjusted according to specific needs. In the present invention, the gradient change of the component x6 is specifically that the medium-wave device gradually increases from 0.2 to 0.45.

[0014] Furthermore, in the above detector, the relatively wide bandgap heavily doped p-type Hg 1-x7 Cd x7 The thickness of the Te contact layer is 1.5 μm. 1-x7 Cd x7 The Te contact layer is made of HgCdTe material with As ion implantation combined with high temperature annealing, and the peak doping concentration is N A ≥1×10 19 cm -3 , the characteristic length is 0.25μm, and the components can be adjusted according to the specific response band needs. The component x7 in the present invention specifically uses 0.45 for medium-wave devices.

[0015] A method for preparing the double transition layer + G + G - νG + G - N + A method for a mercury cadmium telluride multilayer heterojunction device comprises the following steps:

[0016] (1) The double-sided polished epitaxial grade (211) B-face CZT substrate is glued to a heated molybdenum plate and then placed in the sample chamber of a molecular beam epitaxy system for low-temperature pre-degassing treatment to remove moisture adhering to the surface, and then transferred to a growth chamber for deoxidation to remove the oxide layer.

[0017] (2) After deoxidation, the HgCdTe epitaxial layer structure is grown. First, In doping with a wide bandgap n-type Hg1-x1 Cd x1 Te contact layer growth: the Te beam source furnace is heated to the required temperature, the CdTe beam source furnace is heated to the predetermined temperature, and the In beam source furnace is heated to the predetermined temperature. During the growth process, the shutter of the In beam source furnace is opened to perform in-situ doping of the In element, and a 2μm thick HgCdTe epitaxial layer is grown;

[0018] (3) Lower the temperature of the In beam source furnace to grow lightly doped Hg 1-x2 Cd x2 Te composition gradient transition layer, during the growth process, the CdTe source is gradually cooled to n-type Hg 1-x3 Cd x3 The temperature required for the initial growth of the Te transition layer, and the total thickness of the HgCdTe transition layer is 0.3 μm;

[0019] (4) The CdTe source is gradually heated to n-type Hg 1-x4 Cd x4 The temperature required for the growth of the Te absorption layer is used to grow a 0.3 μm thick HgCdTe transition layer.

[0020] (5)Hg 1-x3 Cd x3 After the Te transition layer is grown, a certain thickness of n-type Hg 1-x4 Cd x4 Te absorption layer, during the growth process, the CdTe source is gradually cooled at a certain rate to form a certain component gradient in the absorption layer, and a 4μm thick absorption layer is grown.

[0021] (6) After the absorption layer is grown, continue to grow lightly doped Hg 1-x5 Cd x5 Te composition gradient transition layer, during the growth process, the CdTe source is gradually cooled to n-type Hg 1-x6 Cd x6 The temperature required for the initial growth of the Te transition layer, and the total thickness of the HgCdTe transition layer is 0.3 μm;

[0022] (7) The CdTe source is gradually heated to p-type Hg 1-x7 Cd x7 The temperature required for the growth of the Te contact layer is used to grow a 0.3 μm thick HgCdTe transition layer.

[0023] (8) Turn off the In beam source furnace to grow Hg with a wider bandgap 1-x7 Cd x7 Te contact layer;

[0024] (9) After the epitaxial structure material is grown, the sample is implanted with As ions. After the implantation is completed, the sample is placed in an annealing furnace and sealed and annealed at two temperatures of 400°C / 60mins+240°C / 48h under Hg saturation conditions to achieve As ion activation and Hg vacancy compensation, completing the p-type Hg 1-x7 Cd x7 Te contact layer preparation.

[0025] This completes the preparation of the entire device.

[0026] The double transition layer P provided by the present invention + G + G - νG + G - N + HgCdTe multilayer heterojunction devices have the following benefits:

[0027] 1. The double transition layer P provided by the present invention + G + G - νG + G - N + HgCdTe multilayer heterojunction device has a high-efficiency structure with a high-efficiency structure in the absorption layer ν and the electrode layer N + and P + Two transition layers G are added between the layers + and G - , where the transition layer G - Components from high to low, transition layer G + The composition of the absorption layer changes from low to high, thus forming a low-lying region between the two transition layers. This low-lying region can effectively improve the absorption layer edge composition increase and thickness shortening caused by the mutual diffusion of components caused by high-temperature As ion activation, thereby improving quantum efficiency.

[0028] 2. Adding a certain component gradient to the absorption layer can form a built-in electric field, which can effectively reduce the impact of interface recombination, accelerate the photogenerated carriers to approach the pn junction, and increase the quantum efficiency;

[0029] 3. After annealing, the three-layer heterojunction formed has a repulsive junction and an extraction junction, which makes the carrier concentration in the absorption region of the device lower than the intrinsic carrier concentration at high temperature, thereby achieving a better Auger suppression effect and effectively reducing the dark current of the device;

[0030] 4. N at both ends of the device + and P + The layer is almost fully transparent to the response spectrum, which has a self-passivation effect and effectively reduces the surface dark current. The end point of the pn junction depletion region is at the wide bandgap layer, which can effectively suppress the tunneling current. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] To further illustrate the specific technical content of the present invention, the following is a detailed description with reference to the embodiments and accompanying drawings, wherein:

[0032] Figure 1 P for the double transition layer + G + G - νG + G - N + Schematic diagram of HgCdTe multilayer heterojunction device;

[0033] Figure 2 P for the double transition layer + G + G - νG + G - N + Doping concentration and Cd composition distribution of HgCdTe multilayer heterojunction devices;

[0034] Figure 3 is the P of the double transition layer in the embodiment + G + G - νG + G - N + Cd composition distribution of HgCdTe multilayer heterojunction devices obtained by secondary ion mass spectrometry (SIMS) before and after high-temperature heat treatment;

[0035] Figure 4 is the P of the double transition layer in the embodiment + G + G - νG + G - N + Schematic diagram of the energy band structure of a HgCdTe multilayer heterojunction device at a reverse bias of 0.5V and a temperature of 200K after the junction is formed;

[0036] Figure 5 is the P of the double transition layer in the embodiment + G + G - νG + G - N + The electron and hole concentration distribution of the HgCdTe multilayer heterojunction device at a reverse bias of 0.5V and a temperature of 200K after the junction is formed;

[0037] Figure 1 Middle: 1—CdZnTe substrate, 2—n-type Hg with relatively wide bandgap and heavy doping 1-x1 Cd x1 Te contact layer (N +), 3—lightly doped Hg 1-x2 Cd x2 Te composition gradient transition layer (G - ), 4—lightly doped n-type Hg 1-x3 Cd x3 Te transition layer (G + ), 5—narrow bandgap lightly doped n-type Hg 1-x4 Cd x4 Te component absorption layer (ν), 6-lightly doped Hg 1-x5 Cd x2 Te composition gradient transition layer (G - ), 7—lightly doped Hg 1-x6 Cd x6 Te composition gradient transition layer (G + ), 8—wider bandgap heavily doped p-type Hg 1-x7 Cd x7 Te contact layer (P + ). DETAILED DESCRIPTION

[0038] The technical solution of the present invention is further described below in conjunction with the accompanying drawings, which constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention.

[0039] like Figure 1 、 Figure 2 as well as Figure 4 、 Figure 5 As shown, a double transition layer P + G + G - νG + G - N + HgCdTe multilayer heterojunction devices include CdZnTe (Cd 1-y Zn y Te, CZT) substrate and HgCdTe (Hg 1-x Cd x Te, MCT) epitaxial structure, the epitaxial structure starting from the cadmium zinc telluride substrate is: heavily doped wide band gap n-type Hg 1-x1 Cd x1 Te contact layer (N + layer), lightly doped n-type Hg 1-x2 Cd x2 The gradient transition layer (G - layer), lightly doped n-type Hg 1-x3 Cd x3 The gradient transition layer with low to high Te composition (G + layer), narrow bandgap lightly doped n-type Hg 1-x4 Cdx4 Te absorption layer (ν layer), lightly doped n-type Hg 1-x5 Cd x5 The gradient transition layer (G - layer), lightly doped n-type Hg 1-x6 Cd x6 The gradient transition layer with low to high Te composition (G + layer), heavily doped with wide-bandgap p-type Hg 1-7 Cd x7 Te contact layer (P + layer).

[0040] As an embodiment, the CZT substrate adopts a (211) B-face CZT substrate.

[0041] As an example, the relatively wide bandgap heavily doped n-type Hg 1-x1 Cd x1 The thickness of the Te contact layer is 2 μm, and the material is In-doped HgCdTe material with a doping concentration of (1 to 5)×10 16 cm -3 The Cd component is adjusted according to the component of the absorption layer. Taking the medium-wave device as an example, the component x1 is 0.45.

[0042] As an example, the lightly doped Hg 1-x2 Cd x2 The thickness of the Te composition gradient transition layer is 0.3 μm. The material is In-doped n-type HgCdTe material with a doping concentration of N D ≤1×10 14 cm -3 .Hg 1-x2 Cd x2 The composition x2 in the Te composition gradient transition layer changes from Hg 1-x1 Cd x1 The high composition of the Te contact layer is gradually reduced to Hg 1-x3 Cd x3 The low component used at the beginning of the Te transition layer is adjusted according to specific needs. The gradient change of the component x2 is specifically used to gradually decrease from 0.45 to 0.2, taking the medium-wave device as an example.

[0043] As an example, the lightly doped Hg 1-x3 Cd x3 The thickness of the Te composition gradient transition layer is 0.3 μm. The material is In-doped N-type HgCdTe material with a doping concentration of N D ≤1×10 14 cm -3 , Hg 1-x3 Cd x3The composition x3 in the Te composition gradient transition layer changes from N-type Hg 1-x2 Cd x2 The low composition used at the end of the Te transition layer gradually increases to Hg 1-x4 Cd x4 The components used in the Te absorption layer are adjusted according to specific needs. The gradient change of the component x3 is specifically increased from 0.2 to 0.3, taking the medium-wave device as an example.

[0044] As an example, the narrow bandgap lightly doped n-type Hg 1-x4 Cd x4 The thickness of the Te absorption layer is 4 μm. 1- x4 Cd x4 The Te absorption layer uses In-doped HgCdTe material with a doping concentration of N D ≤1×10 14 cm -3 A certain component gradient is added to the absorption layer, and the component can be adjusted according to specific needs. For example, the component x4 is reduced from 0.3 to 0.295 for a medium-wave device.

[0045] As an example, the lightly doped n-type Hg 1-x5 Cd x5 The thickness of the Te composition gradient transition layer is 0.3 μm. The material is In-doped HgCdTe material, and the doping concentration is reduced to N D ≤1×10 14 cm -3 .Hg 1-x5 Cd x5 The composition x5 in the Te composition gradient transition layer changes from Hg 1-x4 Cd x4 The composition of the Te absorption layer gradually decreases to Hg 1-x6 Cd x6 The components used initially in the Te transition layer are adjusted according to specific needs. The gradient change of the component x5 is specifically that the medium-wave device gradually decreases from 0.295 to 0.2.

[0046] As an example, the lightly doped n-type Hg 1-x6 Cd x6 The thickness of the Te composition gradient transition layer is 0.3 μm. The material is In-doped HgCdTe material, and the doping concentration is reduced to N D ≤1×10 14 cm -3 .Hg 1-x6 Cd x6 The composition x6 in the Te composition gradient transition layer changes from Hg 1-x5 Cd x5The low composition used at the end of the Te transition layer gradually increases to Hg 1-x7 Cd x7 The components used in the Te contact layer are adjusted according to specific needs. The gradient change of the component x6 is specifically that the medium-wave device gradually increases from 0.2 to 0.45.

[0047] As an example, the relatively wide bandgap heavily doped p-type Hg 1-x7 Cd x7 The thickness of the Te contact layer is 1.5 μm. 1- x7 Cd x7 The Te contact layer is made of HgCdTe material with As ion implantation combined with high temperature annealing, and the peak doping concentration is N A ≥1×10 19 cm -3 , the characteristic length is 0.25μm, and the components can be adjusted according to the specific response band needs. This component x7 specifically uses 0.45 for medium-wave devices.

[0048] A method for preparing the double transition layer + G + G - νG + G - N + A method for a mercury cadmium telluride multilayer heterojunction device, comprising:

[0049] The double-sided polished epitaxial grade (211) B-side CZT substrate is glued to a heated molybdenum plate and then placed in the injection chamber of a molecular beam epitaxy system for low-temperature pre-degassing treatment to remove moisture adhering to the surface, and then transferred to a growth chamber for deoxidation to remove the oxide layer.

[0050] After deoxidation is completed, the HgCdTe epitaxial layer structure is grown, and the growth temperature is maintained at around 180°C.

[0051] First, a wide-bandgap In-doped n-type Hg 1-x1 Cd x1 Te contact layer growth, the Te beam source furnace is heated to the required temperature, the CdTe beam source furnace is heated to the predetermined temperature, the In beam source furnace is heated to the predetermined temperature, and the shutter of the In beam source furnace is opened during the growth process to perform in-situ doping of the In element, and a total of 2μm thick HgCdTe epitaxial layer is grown; the temperature of the In beam source furnace is lowered to grow lightly doped Hg 1-x2 Cd x2 Te composition gradient transition layer, during the growth process, the CdTe source is gradually cooled to n-type Hg 1-x3 Cd x3 The temperature required for the growth of the Te transition layer is used to grow a 0.3 μm thick HgCdTe transition layer; the CdTe source is gradually heated to the n-type Hg1-x4 Cd x4 The temperature required for the growth of the Te absorption layer is to grow a 0.3 μm thick HgCdTe transition layer; 1-x3 Cd x3 After the Te transition layer is grown, a certain thickness of n-type Hg 1-x4 Cd x4 During the growth process of the Te absorption layer, the CdTe source is gradually cooled at a certain rate to form a certain composition gradient in the absorption layer, and a 4μm thick absorption layer is grown. After the absorption layer is grown, the lightly doped Hg 1-x5 Cd x5 Te composition gradient transition layer, during the growth process, the CdTe source is gradually cooled to n-type Hg 1-x6 Cd x6 The temperature required for the growth of the Te transition layer is used to grow a total of 0.3 μm thick HgCdTe transition layer; the CdTe source is gradually heated to a p-type Hg 1-x7 Cd x7 The temperature required for the growth of the Te contact layer is used to grow a 0.3 μm thick HgCdTe transition layer; the In beam source furnace is turned off to grow a wide-bandgap heavily doped p-type Hg 1-x7 Cd x7 After the epitaxial structure material is grown, the sample is implanted with As ions. After implantation, the sample is placed in an annealing furnace and sealed for annealing under Hg saturation conditions at two temperatures: 400°C / 60 minutes + 240°C / 48 hours. This activates the As ions and fills the Hg vacancies, completing the preparation of p-type HgCdTe.

[0052] At this point, the preparation of the non-equilibrium mode HgCdTe multilayer heterojunction device has been completed.

[0053] The devices after growth and high temperature annealing were tested using secondary ion mass spectrometry (SIMS) to obtain the Cd composition distribution with thickness as shown in the figure. Figure 3 shown.

[0054] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A double-transition layer HgCdTe multilayer heterojunction device, comprising a CdZnTe substrate and HgCdTe deposited on the CdZnTe substrate. 1-x Cd x Te epitaxial structure, characterized in that The epitaxial structure starting from the CdZnTe substrate is as follows: Heavily doped wide bandgap n-type Hg 1-x1 Cd x1 Te contact layer N + , lightly doped n-type Hg 1-x2 Cd x2 Te composition gradient transition layer G - , lightly doped n-type Hg 1-x3 Cd x3 Te composition gradient transition layer G + , narrow bandgap lightly doped n-type Hg 1-x4 Cd x4 Te absorption layer ν, lightly doped n-type Hg 1-x5 Cd x5 Te composition gradient transition layer G - , lightly doped n-type Hg 1-x6 Cd x6 Te composition gradient transition layer G + , heavily doped with wide-bandgap p-type Hg 1-7 Cd x7 Te contact layer P + ; The lightly doped n-type Hg 1-x2 Cd x2 Te composition gradient transition layer G - The composition is from high to low, the lightly doped n-type Hg 1-x3 Cd x3 Te composition gradient transition layer G + The composition is from low to high in the lightly doped n-type Hg 1-x2 Cd x2 Te composition gradient transition layer G - With lightly doped n-type Hg 1-x3 Cd x3 Te composition gradient transition layer G + A Cd component low area is formed between the lightly doped n-type Hg 1-x5 Cd x5 Te composition gradient transition layer G - The composition is from high to low, the lightly doped n-type Hg 1-x6 Cd x6 Te composition gradient transition layer G + The composition is from low to high in the lightly doped n-type Hg 1-x5 Cd x5 Te composition gradient transition layer G - With lightly doped n-type Hg 1-x6 Cd x6 Te composition gradient transition layer G + A Cd component low-lying area is formed between them.

2. The double-transition-layer HgCdTe multilayer heterojunction device according to claim 1, characterized in that: The component of the low-lying area is at least 0.1 lower than that of the absorption area. The low-lying area can effectively reduce the increase in Cd component and the shortening of thickness at the edge of the absorption layer caused by the mutual diffusion of components due to the activation of high-temperature As ions, thereby improving quantum efficiency.

3. The double-transition-layer HgCdTe multilayer heterojunction device according to claim 1, characterized in that: Narrow bandgap lightly doped n-type Hg 1-x4 Cd x4 A built-in electric field is formed in the Te absorption layer ν through a composition gradient. This built-in electric field is used to reduce the impact of interface recombination, accelerate the photogenerated carriers to approach the pn junction and increase the quantum efficiency.

4. The double-transition-layer HgCdTe multilayer heterojunction device according to claim 1, wherein: The heavily doped wide bandgap n-type Hg 1-x1 Cd x1 Te contact layer N + The thickness is 2 μm, and the material is In-doped HgCdTe with a doping concentration of (1~5)× 10 16 cm -3 , the component x1 is 0.1~0.15 larger than the component of the absorption layer.

5. The double-transition-layer HgCdTe multilayer heterojunction device according to claim 1, characterized in that: The lightly doped Hg 1-x2 Cd x2 The thickness of the Te component gradient transition layer is 0.3 μm, and the material is In-doped n-type HgCdTe material with a doping concentration of N D ≤1×10 14 cm -3 , Hg 1-x2 Cd x2 The composition x2 in the Te composition gradient transition layer changes from Hg 1-x1 Cd x1 The high composition of the Te contact layer is gradually reduced to Hg 1-x3 Cd x3 The Te transition layer starts with a low composition, and the composition x2 gradient gradually decreases from 0.45 to 0.

2.

6. The double-transition-layer HgCdTe multilayer heterojunction device according to claim 1, characterized in that: The lightly doped Hg 1-x3 Cd x3 The thickness of the Te component gradient transition layer is 0.3 μm, and the material is In-doped N-type HgCdTe material with a doping concentration of N D ≤1×10 14 cm -3 , Hg 1-x3 Cd x3 The composition x3 in the Te composition gradient transition layer changes from N-type Hg 1-x2 Cd x2 The low composition used at the end of the Te transition layer gradually increases to Hg 1-x4 Cd x4 The components used in the Te absorption layer, component x3, gradually increase from 0.2 to 0.

3.

7. The double-transition-layer HgCdTe multilayer heterojunction device according to claim 1, characterized in that: The narrower bandgap lightly doped n-type Hg 1-x4 Cd x4 The thickness of the Te absorption layer is 4 μm; the Hg 1-x4 Cd x4 The Te absorption layer uses In-doped HgCdTe material with a doping concentration of N D ≤1×10 14 cm -3 ; A composition gradient is formed in the absorption layer, and the composition x4 decreases from 0.3 to 0.

295.

8. The double-transition-layer HgCdTe multilayer heterojunction device according to claim 1, characterized in that: The lightly doped n-type Hg 1-x5 Cd x5 The thickness of the Te component gradient transition layer is 0.3 μm, and the material is In-doped HgCdTe material, and the doping concentration is reduced to N D ≤1×10 14 cm -3 , Hg 1-x5 Cd x5 The composition x5 in the Te composition gradient transition layer changes from Hg 1-x4 Cd x4 The composition of the Te absorption layer gradually decreases to Hg 1-x6 Cd x6 The composition x5 used at the beginning of the Te transition layer gradually decreases from 0.295 to 0.

2.

9. The double-transition-layer HgCdTe multilayer heterojunction device according to claim 1, characterized in that: The lightly doped n-type Hg 1-x6 Cd x6 The thickness of the Te component gradient transition layer is 0.3 μm; the material is In-doped HgCdTe material, and the doping concentration is reduced to N D ≤1×10 14 cm -3 ; Hg 1-x6 Cd x6 The composition x6 in the Te composition gradient transition layer changes from Hg 1-x5 Cd x5 The low composition used at the end of the Te transition layer gradually increases to Hg 1-x7 Cd x7 The composition of the Te contact layer, component x6, gradually increases from 0.2 to 0.

45.

10. The double-transition-layer HgCdTe multilayer heterojunction device according to claim 1, characterized in that: The heavily doped wide bandgap p-type Hg 1-x7 Cd x7 The thickness of the Te contact layer is 1.5 μm, and the Hg 1-x7 Cd x7 The Te contact layer is made of HgCdTe material with As ion implantation combined with high temperature annealing, and the peak doping concentration is N A ≥1×10 19 cm -3 , the characteristic length is 0.25μm, and the component x7 uses 0.

45.

11. The double-transition-layer HgCdTe multilayer heterojunction device according to any one of claims 1 to 10, characterized in that: The CdZnTe substrate is a CZT substrate with a (211) B surface.

12. A method for preparing a double-transition layer HgCdTe multilayer heterojunction device according to any one of claims 1 to 11, characterized in that: The following steps are involved: (1) The double-sided polished epitaxial grade (211) B-face CZT substrate is glued to a heated molybdenum plate and then placed in the sample chamber of the molecular beam epitaxy system for low-temperature pre-degassing to remove the water vapor adhering to the surface, and then transferred to the growth chamber for deoxidation to remove the oxide layer; (2) After deoxidation, the HgCdTe epitaxial layer structure is grown. First, the wide-bandgap In-doped n-type Hg 1- x1 Cd x1 Te contact layer growth: The Te beam source furnace is heated to the required temperature, the CdTe beam source furnace is heated to the predetermined temperature, and the In beam source furnace is heated to the predetermined temperature. During the growth process, the shutter of the In beam source furnace is opened to perform in-situ doping of the In element, and a total of 2 µm thick HgCdTe epitaxial layer is grown; (3) Lower the temperature of the In beam source furnace to grow lightly doped Hg 1-x2 Cd x2 Te composition gradient transition layer, during the growth process, the CdTe source is gradually cooled to n-type Hg 1-x3 Cd x3 The temperature required for the initial growth of the Te transition layer, and a 0.3 µm thick HgCdTe transition layer is grown; (4) The CdTe source is gradually heated to n-type Hg 1-x4 Cd x4 The temperature required for the growth of the Te absorption layer and the growth of a 0.3 µm thick HgCdTe transition layer; (5) Hg 1-x3 Cd x3 After the Te transition layer is grown, the n-type Hg 1-x4 Cd x4 Te absorption layer, during the growth process, the CdTe source is gradually cooled at a certain rate to form a composition gradient in the absorption layer, and a total of 4 µm thick absorption layer is grown; (6) After the absorption layer is grown, continue to grow lightly doped Hg 1-x5 Cd x5 Te composition gradient transition layer, during the growth process, the CdTe source is gradually cooled to n-type Hg 1-x6 Cd x6 The temperature required for the initial growth of the Te transition layer, which is used to grow a total of 0.3µm thick HgCdTe transition layer; (7) The CdTe source is gradually heated to p-type Hg 1-x7 Cd x7 The temperature required for the growth of the Te contact layer is used to grow a 0.3 µm thick HgCdTe transition layer. (8) Turn off the In beam source furnace to grow Hg with a wider bandgap 1-x7 Cd x7 Te contact layer; (9) After the epitaxial structure material is grown, the sample is implanted with As ions. After the implantation is completed, the sample is placed in an annealing furnace and sealed and annealed at two temperatures of 400°C / 60mins+240°C / 48h under Hg saturation conditions to achieve As ion activation and Hg vacancy compensation, completing the p-type Hg 1-x7 Cd x7 Te contact layer preparation.

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