ZnTe buffer layer-containing cadmium zinc telluride film and preparation method and application thereof

Abstract

The invention belongs to the technical field of semiconductor material preparation, and particularly discloses a ZnTe buffer layer-containing cadmium zinc telluride film and a preparation method and application thereof. According to the invention, a ZnTe polycrystalline wafer and a tellurium-zinc-cadmium polycrystalline wafer are respectively used as evaporation sources, the two evaporation sources are simultaneously arranged in a cavity of a near-space sublimation furnace, and a uniform ZnTe buffer layer and a high-quality tellurium-zinc-cadmium single crystal film are continuously and sequentially deposited on a substrate under the condition that the furnace cavity does not need to be opened to damage a vacuum condition. And the heterojunction interface formed by the prepared ZnTe and CdZnTe has excellent cleanliness and flatness. The thin film formed by the ZnTe buffer layer and the CdZnTe single crystal layer prepared by the method is high in quality and shows important industrial application value in the photoelectric application field of radiation detectors and the like, and the method has the advantages of being high in preparation efficiency, simple and convenient to operate, capable of avoiding cross contamination and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor material preparation, and in particular relates to a cadmium zinc telluride thin film containing a ZnTe buffer layer, a preparation method thereof, and an application thereof. Background Art

[0002] Cadmium zinc telluride (Cd 1-x Zn x CdZnTe (abbreviated as CdZnTe) is a II-VI compound semiconductor material formed by solid solution of cadmium telluride and zinc telluride in a specific ratio. With its high atomic number, adjustable bandgap, and excellent photoelectric conversion performance, CdZnTe shows broad application prospects in the field of high-energy radiation detection. Compared with traditional scintillator detectors, CdZnTe detectors can directly achieve photoelectric conversion at room temperature, without the need for complex cryogenic cooling systems, making them more compact and portable. In addition, the high charge collection efficiency and low dark current characteristics of CdZnTe material give it high energy resolution, enabling accurate identification of radiation signals of different energies. These excellent properties make CdZnTe of great value in high-end applications such as medical imaging, radiation monitoring, and space exploration.

[0003] The traditional melt method for preparing CdZnTe suffers from slow crystal growth rates, multiple growth steps, and complex subsequent processing, resulting in high growth costs. However, the near-space sublimation method (CSS) offers simple equipment, convenient operation, and high raw material utilization, significantly reducing the cost of preparing CdZnTe. To meet the accuracy requirements of radiometric detectors, CdZnTe films are generally required to be high-quality single crystals. However, due to the large lattice mismatch and thermal expansion coefficient difference between the substrates (such as GaAs and GaSb) commonly used for epitaxial growth of CdZnTe single crystal films and CdZnTe, the resulting CdZnTe films have high dislocation and defect densities, resulting in poor film quality, which significantly affects the performance of the detector device.

[0004] To alleviate this problem, a buffer layer is typically introduced between the substrate and the CdZnTe film to reduce the lattice mismatch and improve epitaxial growth quality. However, in conventional processes, the deposition of the buffer layer and CdZnTe film requires opening a chamber and replacing the evaporation source. This can easily lead to interface contamination and oxidation, forming non-ideal interface states, affecting the film's crystal quality and, in turn, reducing the device's carrier mobility and detection efficiency.

[0005] Therefore, it is urgent to develop a continuous preparation method for the buffer layer and the CdZnTe thin film to achieve seamless deposition of both in a single device, so as to reduce interface contamination, improve film quality, and simplify the preparation process. Summary of the Invention

[0006] In response to the technical problems involved in the above-mentioned prior art, the present invention will provide a CdZnTe thin film containing a ZnTe buffer layer and a preparation method and application thereof to improve the quality of the CdZnTe thin film.

[0007] To achieve the above objectives, the following technical solutions are specifically included:

[0008] In a first aspect, the present invention provides a method for preparing a cadmium zinc telluride thin film containing a ZnTe buffer layer, comprising the following steps:

[0009] (1) placing a substrate on an upper heating stage in a close-space sublimation device, placing a ZnTe multi-crystal wafer and a CdZnTe multi-crystal wafer on a lower heating stage in the close-space sublimation device, the substrate and the ZnTe multi-crystal wafer being arranged opposite to each other up and down, and placing a baffle on the surface of the CdZnTe multi-crystal wafer;

[0010] (2) preheating the substrate under vacuum, then heating the substrate and the ZnTe multi-wafer to a first temperature and a second temperature respectively under an inert gas atmosphere, growing ZnTe on the substrate, and obtaining a substrate containing a ZnTe buffer layer after cooling;

[0011] (3) Under an inert gas atmosphere, removing the baffle on the surface of the CdZnTe multi-wafer, and placing the substrate containing the ZnTe buffer layer and the CdZnTe multi-wafer opposite to each other in an upper and lower direction;

[0012] (4) heating the substrate containing the ZnTe buffer layer and the CdZnTe multi-wafer to a third temperature and a fourth temperature, respectively, under an inert gas atmosphere, and growing CdZnTe on the substrate containing the ZnTe buffer layer, and obtaining a ZnTe / CdZnTe heterojunction after cooling;

[0013] (5) The ZnTe / CdZnTe heterojunction and the Te annealing source are placed in an annealing device and heated to a fifth temperature and a sixth temperature, respectively, for annealing. After cooling, a cadmium zinc telluride thin film containing a ZnTe buffer layer is obtained.

[0014] Herein, “ / ” in “ZnTe / CdZnTe” represents “and”.

[0015] Near-space sublimation equipment is generally equipped with an upper heating platform and a lower heating platform corresponding to each other in spatial position. Generally, the lower heating platform fixes the substance to be evaporated, that is, the evaporation source; the upper heating platform fixes the substrate so that the evaporation source can be deposited and grown into a film on the substrate surface after sublimation.

[0016] The invention uses a ZnTe multi-crystal and a CdZnTe multi-crystal as evaporation sources of a ZnTe buffer layer and a CdZnTe layer, respectively, and places the ZnTe multi-crystal and the CdZnTe multi-crystal evaporation sources together on two independent lower heating stages of a near-space sublimation device; the near-space sublimation device is evacuated and inert gas protection is introduced; when the substrate and the ZnTe multi-crystal evaporation source are heated and the ZnTe buffer layer is grown on the surface of the substrate, a baffle is covered on the surface of the CdZnTe multi-crystal evaporation source, so that the process of growing the ZnTe buffer layer does not contaminate the CdZnTe multi-crystal; the ZnTe buffer After the layer growth is completed, the baffle on the surface of the CdZnTe multi-wafer is removed, and the CdZnTe multi-wafer evaporation source is transferred to the bottom of the substrate to grow the CdZnTe single crystal film. When replacing the CdZnTe multi-wafer evaporation source, the evaporation source can be replaced without opening the near-space sublimation equipment cavity, avoiding interface contamination and oxidation caused by the equipment cavity switching process, simplifying the process, improving the interface quality of the cadmium zinc telluride film and the buffer layer, realizing the continuous preparation of the cadmium zinc telluride film and its buffer layer, and improving the quality of the zinc cadmium film; and then after annealing treatment, a high-quality single crystal phase cadmium zinc telluride film is obtained.

[0017] Preferably, in step (1), the ZnTe multi-crystal is further subjected to polishing, ultrasonic cleaning and drying pretreatment in sequence, the solvent of the ultrasonic cleaning comprises at least one of acetone, ethanol or deionized water, and the ultrasonic cleaning time is 10-20 minutes. The pretreatment can remove the oxide layer and pollutants on the surface of the ZnTe multi-crystal, and improve the quality of the subsequent precipitated ZnTe buffer layer. The ZnTe multi-crystal can be a homemade multi-crystal or a commercially available multi-crystal. The ZnTe multi-crystal includes ZnTe polycrystals grown by the Bridgman method or the mobile heater method.

[0018] Preferably, in step (1), the CdZnTe multi-crystalline wafer is further subjected to polishing, ultrasonic cleaning, and drying pretreatment in sequence, wherein the ultrasonic cleaning solvent comprises at least one of acetone, ethanol, or deionized water, and the ultrasonic cleaning time is 10-20 minutes. The pretreatment can remove the oxide layer and contaminants on the surface of the CdZnTe multi-crystalline wafer, thereby improving the quality of the subsequently deposited CdZnTe layer.

[0019] Preferably, in step (1), the chemical expression of the CdZnTe multi-crystalline wafer is Cd 1-x Zn x Te, wherein 0.01≤x≤0.2. The CdZnTe polycrystalline wafer can be a homemade polycrystalline wafer or a commercially available polycrystalline wafer. The CdZnTe polycrystalline wafer includes CdZnTe polycrystalline grown by the Bridgman method or the moving heater method.

[0020] Preferably, in step (1), the substrate comprises at least one of GaAs with a (100) crystal plane or GaSb with a (100) crystal plane.

[0021] Preferably, in step (1), the substrate is further subjected to ultrasonic cleaning, the solvent of the ultrasonic cleaning comprises at least one of acetone, ethanol or deionized water, and the time of the ultrasonic cleaning is 10-20 minutes.

[0022] Preferably, in step (1), the distance between the substrate and the ZnTe multi-crystalline wafer is 1-10 mm.

[0023] Preferably, in step (2), the vacuum pressure is less than or equal to 0.1 Pa, and more preferably less than or equal to 0.01 Pa.

[0024] Preferably, in step (2), the temperature of the preheating treatment is 500-700° C., and the time of the preheating treatment is 5-20 minutes. The preheating treatment can remove oxides and possible impurities on the surface of the substrate.

[0025] Preferably, in steps (2), (3) and (4), the inert gas independently comprises at least one of argon, nitrogen or helium.

[0026] Preferably, in step (2), the first temperature is 200-450°C.

[0027] Preferably, in step (2), the second temperature is 650-730°C.

[0028] Preferably, in step (2), the growth time is 3-10 minutes.

[0029] Preferably, in step (2), the heating rate when heating to the first temperature is 1-5°C / s.

[0030] Preferably, in step (2), the heating rate when heating to the second temperature is 1-5°C / s.

[0031] Preferably, in step (2), the cooling is natural cooling.

[0032] Preferably, in step (2), if the ZnTe polycrystalline wafer remains after obtaining the substrate containing the ZnTe buffer layer, a baffle is provided on the surface of the remaining ZnTe polycrystalline wafer to prevent contamination thereof so that the remaining ZnTe polycrystalline wafer can be reused. For greater convenience, baffles can be pre-designed on both evaporation sources to ensure that the evaporation sources can operate independently without interfering with each other, thereby making the composition of the deposited film more controllable.

[0033] Preferably, in step (3), the distance between the substrate containing the ZnTe buffer layer and the CdZnTe polycrystalline wafer is 1-10 mm.

[0034] Preferably, in step (4), the third temperature is 200-560° C. By controlling the temperature of the substrate, the growth rate of CdZnTe can be regulated and the quality of the CdZnTe layer can be improved.

[0035] Preferably, in step (4), the fourth temperature is 650-730°C.

[0036] Preferably, in step (4), the growth time is 2-8 hours.

[0037] Preferably, in step (4), the heating rate when heating to the third temperature is 1-5°C / s.

[0038] Preferably, in step (4), the heating rate when heating to the fourth temperature is 1-5°C / s.

[0039] Preferably, in step (4), the cooling is natural cooling.

[0040] Preferably, in step (5), the fifth temperature is 350-400°C.

[0041] Preferably, in step (5), the sixth temperature is 380-420°C.

[0042] Preferably, in step (5), the annealing time is 2-10 hours.

[0043] Preferably, in step (5), the heating rate when heating to the fifth temperature is 10-30°C / min.

[0044] Preferably, in step (5), the heating rate when heating to the sixth temperature is 10-30°C / min.

[0045] By controlling the annealing temperature and the heating rate, the internal stress in the crystal is improved, the crystal quality of the cadmium zinc telluride containing the ZnTe buffer layer is improved, and the purpose of improving the electrical performance is achieved.

[0046] In a second aspect, the present invention provides a cadmium zinc telluride thin film containing a ZnTe buffer layer, comprising a ZnTe buffer layer and a CdZnTe layer stacked in sequence, and is prepared by the method for preparing a cadmium zinc telluride thin film containing a ZnTe buffer layer.

[0047] Preferably, the ZnTe in the ZnTe buffer layer is single crystal, and the CdZnTe in the CdZnTe layer is single crystal. The preparation method of the present invention can make both the ZnTe buffer layer and the CdZnTe layer single crystal, thereby improving their electrical properties.

[0048] Preferably, the thickness of the ZnTe buffer layer is 3-30 μm.

[0049] Preferably, the thickness of the CdZnTe layer is 100-1200 μm.

[0050] In a third aspect, the present invention provides a radiation detector comprising the aforementioned CdZnTe thin film containing a ZnTe buffer layer. The CdZnTe thin film containing a ZnTe buffer layer of the present invention has high crystalline quality and excellent film quality. When assembled as a component of a radiation detector, it can improve the device's carrier mobility and detection efficiency.

[0051] Compared to existing technologies, the present invention offers the following advantages: It allows for the continuous deposition of a ZnTe buffer layer and the epitaxial growth of a CdZnTe thin film within a single device, avoiding interface contamination caused by opening a chamber to replace the evaporation source. This improves the interface quality between the buffer layer and the CdZnTe thin film, resulting in films with higher crystalline quality and electrical properties. Furthermore, the present invention offers a simple, low-cost, and highly controllable preparation process, promising the large-scale production of high-quality CdZnTe thin films and rapidly promoting their application in high-energy radiation detectors. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 The schematic diagram of the present invention for depositing a ZnTe buffer layer and a CdZnTe thin film, wherein the near-space sublimation apparatus includes a chamber, wherein the chamber includes an upper heating stage located in the upper half of the chamber and fixed above the interior of the chamber, and the substrate is fixedly connected to the upper heating stage by a clamp; further comprising two independent lower heating stages located in the lower half of the chamber and movable, wherein the two lower heating stages are movable horizontally and vertically by movable rods disposed at the bottoms of the two lower heating stages, and each heating stage can be heated by infrared; the ZnTe multi-wafer and the CdZnTe multi-wafer are independently fixed to the upper surfaces of the two lower heating stages; further comprising at least one movable baffle disposed in the middle of the chamber, such as Figure 1 As shown in , a baffle is respectively provided above the two lower heating stages; Figure 1 ZnTe in the table represents ZnTe polycrystalline, and CdZnTe represents CdZnTe polycrystalline. Figure 1 The left picture in the middle is a schematic diagram of the deposition of the ZnTe buffer layer, and the right picture is a schematic diagram of the deposition of the CdZnTe layer. The positions of the two evaporation sources, the ZnTe polycrystalline wafer and the CdZnTe polycrystalline wafer, are controlled by moving the rod to switch the evaporation material.

[0053] Figure 2 This is the XRD spectrum of the substrate containing the ZnTe buffer layer in Example 1.

[0054] Figure 3This is the XRD spectrum of the cadmium zinc telluride thin film containing the ZnTe buffer layer in Example 1. DETAILED DESCRIPTION

[0055] To better illustrate the objectives, technical solutions, and advantages of the present invention, the present invention will be further described below with reference to specific examples. The experimental methods used in the examples and / or comparative examples are conventional methods unless otherwise specified; the materials and reagents used are commercially available unless otherwise specified.

[0056] Example 1

[0057] A method for preparing a cadmium zinc telluride thin film containing a ZnTe buffer layer, as shown in the schematic diagram Figure 1 As shown, the specific steps include:

[0058] (1) Evaporation source and substrate pretreatment:

[0059] ZnTe polycrystals and Cd grown by Bridgman method or moving heater method 0.9 Zn 0.1 Te polycrystals were used as evaporation sources. After the crystals were cut into slices, the surface of the polycrystalline wafers was first polished with sandpaper to remove the oxide layer. The polished polycrystalline wafers were then placed in acetone, anhydrous ethanol, and deionized water for 15 minutes each. Finally, they were blown dry with nitrogen and vacuum-sealed for later use. The pre-treated ZnTe polycrystalline wafers and CdZnTe polycrystalline wafers were obtained.

[0060] GaAs (100) was used as the growth substrate. The substrate was placed in acetone, anhydrous ethanol and deionized water in sequence and ultrasonicated for 15 minutes each to remove impurities adsorbed on the surface. Finally, it was dried with nitrogen and vacuum-sealed for standby use to obtain the pretreated substrate.

[0061] (2) ZnTe buffer layer growth:

[0062] The pre-treated ZnTe multi-wafer, CdZnTe multi-wafer and substrate are placed in a close-space sublimation furnace, wherein the ZnTe multi-wafer and CdZnTe multi-wafer are placed on two independent lower heating stages, and the substrate is fixed on the upper heating stage by a clamp;

[0063] The lower heating stage carrying the ZnTe multi-wafer is moved to the bottom of the upper heating stage by moving the rod, and the upper part of the CdZnTe multi-wafer is covered with a baffle;

[0064] Turn on the mechanical pump and the vent valve to evacuate the chamber, turn on the water cooling, and when the pressure in the chamber is lower than 5Pa, the molecular pump will automatically start, and continue to evacuate to 1×10 -3Pa, preheat the substrate to a constant temperature of 550°C for 20 min to remove oxides and possible impurities on the substrate surface, and then cool the substrate to room temperature;

[0065] High-purity argon gas was introduced to increase the chamber pressure to 0.01 Pa. The distance between the substrate and the evaporation source was adjusted to 5 mm. The substrate and the ZnTe multi-wafer were then heated to 330°C and 700°C, respectively, at a heating rate of 2°C / s. The ZnTe buffer layer was grown at this temperature for 4 minutes. After the growth was completed, the substrate was naturally cooled to room temperature to obtain a substrate containing a ZnTe buffer layer.

[0066] (3) CdZnTe layer growth:

[0067] The molecular pump was used to pump the air pressure in the chamber to 1×10 -3 Pa, and then high-purity argon gas is introduced to increase the pressure in the cavity to 0.01Pa;

[0068] Move the lower heating stage, and move the lower heating stage carrying the CdZnTe multi-wafer to below the substrate of the upper heating stage, keeping the distance between them at 5 mm, and cover the remaining ZnTe multi-wafer with a baffle;

[0069] The ZnTe buffer layer substrate and the CdZnTe multi-wafer were heated to 470°C and 730°C, respectively, at a heating rate of 2°C / s. The CdZnTe layer was grown at this temperature for 8 hours and then cooled naturally to room temperature to obtain a ZnTe / CdZnTe heterojunction.

[0070] Close the vent valve, molecular pump, water cooling, and mechanical pump in sequence, open the cavity, and remove the ZnTe / CdZnTe heterojunction;

[0071] (4) Annealing:

[0072] The ZnTe / CdZnTe heterojunction obtained in step (3) and the Te annealing source are placed in the centers of two temperature zones of the annealing furnace respectively, and the centers of the two temperature zones are heated to 400°C at a heating rate of 30°C / min, and the temperature is maintained for annealing. The annealing time is 2 hours, and after annealing, the film is naturally cooled to room temperature to obtain a cadmium zinc telluride film containing a ZnTe buffer layer.

[0073] Scanning electron microscopy (SEM) was used to characterize the cross-section of the CdZnTe thin film containing a ZnTe buffer layer. The results showed that the film contained a 3μm-thick ZnTe buffer layer and a 1200μm-thick CdZnTe layer. It can be observed that the heterojunction interface between the ZnTe buffer layer and the CdZnTe layer is atomically flat, with excellent cleanliness and flatness.

[0074] The X-ray diffraction (XRD) characterization of the substrate containing the ZnTe buffer layer and the CdZnTe thin film containing the ZnTe buffer layer was performed. Figure 2 and Figure 3 As shown in Figure 3, only one set of characteristic diffraction peaks appears in both of them, which indicates that both the ZnTe buffer layer and the CdZnTe film have a single crystal structure.

[0075] Compared to polycrystalline ZnTe buffer layers prepared by conventional magnetron sputtering, the present invention successfully produces a single-crystal ZnTe buffer layer on a lattice-matched substrate using a close-space sublimation method. This single-crystal buffer layer serves as an ideal epitaxial substrate for epitaxial growth of high-quality single-crystal CdZnTe thin films. The resulting CdZnTe single-crystal thin film exhibits high resistivity and carrier mobility lifetime product, demonstrating excellent radiation detection performance. In contrast, when polycrystalline ZnTe is used as a buffer layer, the resulting CdZnTe film exhibits a polycrystalline state, with numerous grain boundaries and defects within it, making it difficult to meet the crystal quality requirements for high-performance radiation detection.

[0076] The ZnTe buffer layer was prepared using the same process conditions as in Example 1. However, when placing the ZnTe multi-wafer, the CdZnTe multi-wafer was not placed in the close-space sublimation furnace at the same time. After obtaining the ZnTe buffer layer, the close-space sublimation furnace cavity was opened, the ZnTe buffer layer was taken out, and the CdZnTe multi-wafer was placed under the substrate. The mechanical pump and the vent valve were then turned on to evacuate the cavity, and water cooling was turned on. When the pressure in the cavity was lower than 5 Pa, the molecular pump was automatically turned on, and the evacuation was continued to 1×10 -3 Pa, and then a CdZnTe layer was grown using the same process conditions as in Example 1 to obtain a ZnTe / CdZnTe heterojunction thin film. In comparison, the CdZnTe prepared in Example 1 exhibited a smaller XRD half-peak width, higher crystalline quality, and greater carrier mobility due to the clean interface.

[0077] Example 2

[0078] A method for preparing a cadmium zinc telluride thin film containing a ZnTe buffer layer, as shown in the schematic diagram Figure 1 As shown, the specific steps include:

[0079] (1) Evaporation source and substrate pretreatment:

[0080] ZnTe polycrystals and Cd grown by Bridgman method or moving heater method 0.9 Zn 0.1Te polycrystals were used as evaporation sources. After the crystals were cut into slices, the surface of the polycrystalline wafers was first polished with sandpaper to remove the oxide layer. The polished polycrystalline wafers were then placed in acetone, anhydrous ethanol, and deionized water for 15 minutes each. Finally, they were blown dry with nitrogen and vacuum-sealed for later use. The pre-treated ZnTe polycrystalline wafers and CdZnTe polycrystalline wafers were obtained.

[0081] GaAs (100) was used as the growth substrate. The substrate was placed in acetone, anhydrous ethanol and deionized water in sequence and ultrasonicated for 15 minutes each to remove impurities adsorbed on the surface. Finally, it was dried with nitrogen and vacuum-sealed for standby use to obtain the pretreated substrate.

[0082] (2) ZnTe buffer layer growth:

[0083] The pre-treated ZnTe multi-wafer, CdZnTe multi-wafer and substrate are placed in a close-space sublimation furnace, wherein the ZnTe multi-wafer and CdZnTe multi-wafer are placed on two independent lower heating stages, and the substrate is fixed on the upper heating stage by a clamp;

[0084] The lower heating stage is moved by a moving rod to move the lower heating stage carrying the ZnTe multi-wafer to below the substrate of the upper heating stage, and a baffle is used to cover the top of the CdZnTe multi-wafer;

[0085] Turn on the mechanical pump and the vent valve to evacuate the chamber, turn on the water cooling, and when the pressure in the chamber is lower than 5Pa, the molecular pump will automatically start, and continue to evacuate to 1×10 -3 Pa, preheat the substrate to a constant temperature of 550°C for 20 min to remove oxides and possible impurities on the substrate surface, and then cool the substrate to room temperature;

[0086] High-purity argon gas was introduced to increase the chamber pressure to 0.01 Pa, and the distance between the substrate and the evaporation source was adjusted to 5 mm. The substrate and the ZnTe multi-wafer were then heated to 350°C and 690°C, respectively, at a heating rate of 2°C / s. The ZnTe buffer layer was grown at this temperature for 5 minutes. After the growth was completed, the substrate was naturally cooled to room temperature to obtain a substrate containing a ZnTe buffer layer.

[0087] (3) CdZnTe layer growth:

[0088] The molecular pump was used to pump the air pressure in the chamber to 1×10 -3 Pa, and then high-purity argon gas is introduced to increase the pressure in the cavity to 0.01Pa;

[0089] Move the lower heating stage, and move the lower heating stage carrying the CdZnTe multi-wafer to the bottom of the upper heating stage, keeping the distance between them at 5 mm, and cover the top of the remaining ZnTe multi-wafer with a baffle;

[0090] The ZnTe buffer layer substrate and the CdZnTe multi-wafer were heated to 560°C and 710°C, respectively, at a heating rate of 2°C / s. The CdZnTe layer was grown at this temperature for 2 hours and then cooled naturally to room temperature to obtain a ZnTe / CdZnTe heterojunction.

[0091] Close the vent valve, molecular pump, water cooling, and mechanical pump in sequence, open the cavity, and remove the ZnTe / CdZnTe heterojunction;

[0092] (4) Annealing:

[0093] The ZnTe / CdZnTe heterojunction obtained in step (3) and the Te annealing source are placed in the centers of two temperature zones of the annealing furnace, respectively. The centers of the temperature zones corresponding to the substrate and the annealing source are heated to 380°C and 420°C, respectively, at a heating rate of 30°C / min. The temperatures are maintained for annealing for 2 hours. After annealing, the film is naturally cooled to room temperature to obtain a cadmium zinc telluride film containing a ZnTe buffer layer.

[0094] Scanning electron microscopy (SEM) was used to characterize the cross-section of the CdZnTe thin film containing a ZnTe buffer layer. The results showed that the film contained a 3μm-thick ZnTe buffer layer and a 200μm-thick CdZnTe layer. It can be observed that the heterojunction interface between the ZnTe buffer layer and the CdZnTe layer is atomically flat, with excellent cleanliness and flatness.

[0095] Example 3

[0096] A method for preparing a cadmium zinc telluride thin film containing a ZnTe buffer layer, as shown in the schematic diagram Figure 1 As shown, the specific steps include:

[0097] (1) Evaporation source and substrate pretreatment:

[0098] ZnTe polycrystals and Cd grown by Bridgman method or moving heater method 0.9 Zn 0.1 Te polycrystals were used as evaporation sources. After the crystals were cut into slices, the surface of the polycrystalline wafers was first polished with sandpaper to remove the oxide layer. The polished polycrystalline wafers were then placed in acetone, anhydrous ethanol, and deionized water for 15 minutes each. Finally, they were blown dry with nitrogen and vacuum-sealed for later use. The pre-treated ZnTe polycrystalline wafers and CdZnTe polycrystalline wafers were obtained.

[0099] GaSb(100) was used as the growth substrate. The substrate was placed in acetone, anhydrous ethanol and deionized water in sequence and ultrasonicated for 15 minutes each to remove impurities adsorbed on the surface. Finally, it was blown dry with nitrogen and vacuum-sealed for standby use to obtain the pretreated substrate.

[0100] (2) ZnTe buffer layer growth:

[0101] The pre-treated ZnTe multi-wafer, CdZnTe multi-wafer and substrate are placed in a close-space sublimation furnace, wherein the ZnTe multi-wafer and CdZnTe multi-wafer are placed on two independent lower heating stages, and the substrate is fixed on the upper heating stage by a clamp;

[0102] The lower heating stage is moved by a moving rod to move the lower heating stage carrying the ZnTe multi-wafer to below the substrate of the upper heating stage, and a baffle is used to cover the top of the CdZnTe multi-wafer;

[0103] Turn on the mechanical pump and the vent valve to evacuate the chamber, turn on the water cooling, and when the pressure in the chamber is lower than 5Pa, the molecular pump will automatically start, and continue to evacuate to 1×10 -3 Pa, preheat the substrate to a constant temperature of 550°C for 20 min to remove oxides and possible impurities on the substrate surface, and then cool the substrate to room temperature;

[0104] High-purity argon gas was introduced to increase the chamber pressure to 0.01 Pa, and the distance between the substrate and the evaporation source was adjusted to 6 mm. The substrate and the ZnTe multi-wafer were then heated to 320°C and 680°C, respectively, at a heating rate of 2°C / s. The ZnTe buffer layer was grown at this temperature for 5 minutes. After the growth was completed, the substrate was naturally cooled to room temperature to obtain a substrate containing a ZnTe buffer layer.

[0105] (3) CdZnTe layer growth:

[0106] The molecular pump was used to pump the air pressure in the chamber to 1×10 -3 Pa, and then high-purity argon gas is introduced to increase the pressure in the cavity to 0.01Pa;

[0107] Move the lower heating stage, and move the lower heating stage carrying the CdZnTe multi-wafer to the bottom of the upper heating stage, keeping the distance between them at 5 mm, and cover the top of the remaining ZnTe multi-wafer with a baffle;

[0108] The ZnTe buffer layer substrate and the CdZnTe multi-wafer were heated to 250°C and 710°C, respectively, at a heating rate of 2°C / s. The CdZnTe layer was grown at this temperature for 6 hours and then cooled naturally to room temperature to obtain a ZnTe / CdZnTe heterojunction.

[0109] Close the vent valve, molecular pump, water cooling, and mechanical pump in sequence, open the cavity, and remove the ZnTe / CdZnTe heterojunction;

[0110] (4) Annealing:

[0111] The ZnTe / CdZnTe heterojunction obtained in step (3) and the Te annealing source are placed in the centers of two temperature zones of an annealing furnace, respectively. The centers of the temperature zones corresponding to the substrate and the annealing source are heated to 380°C and 420°C, respectively, at a heating rate of 30°C / min. The temperatures are maintained for annealing for 2 hours. After annealing, the film is naturally cooled to room temperature to obtain a cadmium zinc telluride film containing a ZnTe buffer layer.

[0112] Scanning electron microscopy (SEM) was used to characterize the cross-section of the CdZnTe film containing a ZnTe buffer layer. The results showed that the film contained a 3μm-thick ZnTe buffer layer and a 360μm-thick CdZnTe layer. It can be observed that the heterojunction interface between the ZnTe buffer layer and the CdZnTe layer is atomically flat, with excellent cleanliness and flatness.

[0113] Example 4

[0114] A method for preparing a cadmium zinc telluride thin film containing a ZnTe buffer layer, as shown in the schematic diagram Figure 1 As shown, the specific steps include:

[0115] (1) Evaporation source and substrate pretreatment:

[0116] ZnTe polycrystals and Cd grown by Bridgman method or moving heater method 0.9 Zn 0.1 Te polycrystals were used as evaporation sources. After the crystals were cut into slices, the surface of the polycrystalline wafers was first polished with sandpaper to remove the oxide layer. The polished polycrystalline wafers were then placed in acetone, anhydrous ethanol, and deionized water for 15 minutes each. Finally, they were blown dry with nitrogen and vacuum-sealed for later use. The pre-treated ZnTe polycrystalline wafers and CdZnTe polycrystalline wafers were obtained.

[0117] GaSb(100) was used as the growth substrate. The substrate was placed in acetone, anhydrous ethanol and deionized water in sequence and ultrasonicated for 15 minutes each to remove impurities adsorbed on the surface. Finally, it was blown dry with nitrogen and vacuum-sealed for standby use to obtain the pretreated substrate.

[0118] (2) ZnTe buffer layer growth:

[0119] The pre-treated ZnTe multi-wafer, CdZnTe multi-wafer and substrate are placed in a close-space sublimation furnace, wherein the ZnTe multi-wafer and CdZnTe multi-wafer are placed on two independent lower heating stages, and the substrate is fixed on the upper heating stage by a clamp;

[0120] The lower heating stage is moved by a moving rod to move the lower heating stage carrying the ZnTe multi-wafer to below the substrate of the upper heating stage, and a baffle is used to cover the top of the CdZnTe multi-wafer;

[0121] Turn on the mechanical pump and the vent valve to evacuate the chamber, turn on the water cooling, and when the pressure in the chamber is lower than 5Pa, the molecular pump will automatically start, and continue to evacuate to 1×10 -3 Pa, preheat the substrate to keep it constant at 600 ° C for 10 minutes to remove oxides and possible impurities on the surface of the substrate, and then cool the substrate to room temperature;

[0122] High-purity argon gas was introduced to increase the chamber pressure to 0.01 Pa, and the distance between the substrate and the evaporation source was adjusted to 6 mm. The substrate and the ZnTe multi-wafer were then heated to 230°C and 670°C, respectively, at a heating rate of 2°C / s. The ZnTe buffer layer was grown at this temperature for 5 minutes. After the growth was completed, the substrate was naturally cooled to room temperature to obtain a substrate containing a ZnTe buffer layer.

[0123] (3) CdZnTe layer growth:

[0124] The molecular pump was used to pump the air pressure in the chamber to 1×10 -3 Pa, and then high-purity argon gas is introduced to increase the pressure in the cavity to 0.01Pa;

[0125] Move the lower heating stage, and move the lower heating stage carrying the CdZnTe multi-wafer to the bottom of the upper heating stage, keeping the distance between them at 5 mm, and cover the top of the remaining ZnTe multi-wafer with a baffle;

[0126] The ZnTe buffer layer substrate and the CdZnTe multi-wafer were heated to 235°C and 700°C, respectively, at a heating rate of 2°C / s. The CdZnTe layer was grown at this temperature for 6 hours and then cooled naturally to room temperature to obtain a ZnTe / CdZnTe heterojunction.

[0127] Close the vent valve, molecular pump, water cooling, and mechanical pump in sequence, open the cavity, and remove the ZnTe / CdZnTe heterojunction;

[0128] (4) Annealing:

[0129] The ZnTe / CdZnTe heterojunction obtained in step (3) and the Te annealing source are placed in the centers of two temperature zones of the annealing furnace, respectively. The centers of the temperature zones corresponding to the substrate and the annealing source are heated to 380°C and 410°C, respectively, at a heating rate of 30°C / min. The temperatures are maintained for annealing for 2 hours. After annealing, the film is naturally cooled to room temperature to obtain a cadmium zinc telluride film containing a ZnTe buffer layer.

[0130] Scanning electron microscopy (SEM) was used to characterize the cross-section of the CdZnTe thin film with a ZnTe buffer layer. The results showed that the film contained a 3μm-thick ZnTe buffer layer and a 500μm-thick CdZnTe layer. It can be observed that the heterojunction interface between the ZnTe buffer layer and the CdZnTe layer is atomically flat, with excellent cleanliness and flatness.

[0131] In summary, the present invention uses zinc telluride (ZnTe) multi-crystal and cadmium zinc telluride (Cd 1-x Zn x The method uses a multi-crystal ZnTe (ZnTe, abbreviated as CdZnTe) as an evaporation source. Two evaporation sources are simultaneously placed within the chamber of a near-space sublimation furnace. Without opening the furnace chamber to disrupt vacuum conditions, a uniform ZnTe buffer layer and a high-quality CdZnTe single crystal thin film are sequentially deposited on the substrate. The heterojunction interface formed by the ZnTe and CdZnTe produced exhibits excellent cleanliness and flatness. Compared to traditional single-source evaporation processes, which require chamber opening and source replacement, the method of the present invention produces high-quality single crystal thin films composed of the buffer layer and CdZnTe layer. This method demonstrates significant industrial application value in optoelectronic applications such as radiation detectors. Furthermore, the method offers advantages such as high production efficiency, ease of operation, and the avoidance of cross-contamination.

[0132] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a cadmium zinc telluride thin film containing a ZnTe buffer layer, characterized in that: The steps include: (1) placing a substrate on an upper heating stage in a close-space sublimation device, placing a ZnTe multi-crystal wafer and a CdZnTe multi-crystal wafer on a lower heating stage in the close-space sublimation device, the substrate and the ZnTe multi-crystal wafer being arranged opposite to each other up and down, and placing a baffle on the surface of the CdZnTe multi-crystal wafer; (2) preheating the substrate under vacuum, then heating the substrate and the ZnTe multi-wafer to a first temperature and a second temperature respectively under an inert gas atmosphere, growing ZnTe on the substrate, and obtaining a substrate containing a ZnTe buffer layer after cooling; (3) Under an inert gas atmosphere, removing the baffle on the surface of the CdZnTe multi-wafer, and placing the substrate containing the ZnTe buffer layer and the CdZnTe multi-wafer opposite to each other in an upper and lower direction; (4) heating the substrate containing the ZnTe buffer layer and the CdZnTe multi-wafer to a third temperature and a fourth temperature, respectively, under an inert gas atmosphere, and growing CdZnTe on the substrate containing the ZnTe buffer layer, and obtaining a ZnTe / CdZnTe heterojunction after cooling; (5) The ZnTe / CdZnTe heterojunction and the Te annealing source are placed in an annealing device and heated to a fifth temperature and a sixth temperature, respectively, for annealing. After cooling, a cadmium zinc telluride thin film containing a ZnTe buffer layer is obtained.

2. The method for preparing a cadmium zinc telluride thin film containing a ZnTe buffer layer according to claim 1, wherein: Include at least one of the following AF: A. In step (1), the ZnTe multi-wafer is further subjected to polishing, ultrasonic cleaning and drying pretreatment in sequence; B. In step (1), the CdZnTe multi-wafer is further subjected to polishing, ultrasonic cleaning and drying pretreatment in sequence; C. In step (1), the chemical expression of the CdZnTe multi-crystalline wafer is Cd 1-x Zn x Te, where 0.01≤x≤0.2; D. In step (1), the substrate comprises at least one of GaAs with a (100) crystal plane or GaSb with a (100) crystal plane; E. In step (1), the substrate is further subjected to ultrasonic cleaning; F. In step (1), the distance between the substrate and the ZnTe multi-crystalline wafer is 1-10 mm.

3. The method for preparing a cadmium zinc telluride thin film containing a ZnTe buffer layer according to claim 1, wherein: Include at least one of the following GKs: G. In step (2), the first temperature is 200-450°C; H. In step (2), the second temperature is 650-730°C; I. In step (2), the growth time is 3-10 min; J. In step (2), the heating rate when heating to the first temperature is 1-5°C / s; K. In step (2), the heating rate when heating to the second temperature is 1-5°C / s.

4. The method for preparing a cadmium zinc telluride thin film containing a ZnTe buffer layer according to claim 1, wherein: In step (2), the temperature of the preheating treatment is 500-700° C., and the time of the preheating treatment is 5-20 minutes.

5. The method for preparing a cadmium zinc telluride thin film containing a ZnTe buffer layer according to claim 1, wherein: Include at least one of the following LOs: L. In step (2), the vacuum pressure is less than or equal to 0.1 Pa; M. In steps (2), (3) and (4), the inert gas independently comprises at least one of argon, nitrogen or helium; N. In step (2), the cooling is natural cooling; O. In step (3), the distance between the substrate containing the ZnTe buffer layer and the CdZnTe polycrystalline wafer is 1-10 mm.

6. The method for preparing a cadmium zinc telluride thin film containing a ZnTe buffer layer according to claim 1, wherein: Include at least one of the following PTs: P. In step (4), the third temperature is 200-560°C; Q. In step (4), the fourth temperature is 650-730°C; R. In step (4), the growth time is 2-8h; S. In step (4), the heating rate when heating to the third temperature is 1-5°C / s; T. In step (4), the heating rate when heating to the fourth temperature is 1-5°C / s.

7. The method for preparing a cadmium zinc telluride thin film containing a ZnTe buffer layer according to claim 1, wherein: Include at least one of the following UYs: U. In step (5), the fifth temperature is 350-400° C.; V. In step (5), the sixth temperature is 380-420°C; W. In step (5), the annealing time is 2-10h; X. In step (5), the heating rate when heating to the fifth temperature is 10-30°C / min; Y. In step (5), the heating rate when heating to the sixth temperature is 10-30°C / min.

8. A cadmium zinc telluride thin film containing a ZnTe buffer layer, characterized in that: The invention comprises a ZnTe buffer layer and a CdZnTe layer stacked in sequence, and is prepared by the method for preparing a cadmium zinc telluride thin film containing a ZnTe buffer layer according to any one of claims 1 to 7.

9. The cadmium zinc telluride thin film containing a ZnTe buffer layer according to claim 8, wherein: Include at least one of the following items: I. The ZnTe in the ZnTe buffer layer is single crystal, and the CdZnTe in the CdZnTe layer is single crystal; II. The thickness of the ZnTe buffer layer is 3-30 μm; III. The thickness of the CdZnTe layer is 100-1200 μm.

10. A radiation detector, characterized in that: A cadmium zinc telluride thin film comprising a ZnTe buffer layer as claimed in claim 8 or 9.

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