THM crystal growth device and method for preparing tellurium-cadmium compound crystal with low cracking rate

Abstract

The invention belongs to the technical field of growth devices and preparation of tellurium-cadmium compound single crystals, and particularly relates to a THM crystal growth device and a method for preparing tellurium-cadmium compound crystals with a low cracking rate. The device comprises a furnace body, a furnace chamber heater, a liftable lifting support and a driving device of the liftable lifting support. A supporting groove for supporting the quartz crucible is formed in the top of the lifting support, and a heating module comprising an upper heat insulation layer, a bottom support heater and a lower heat insulation layer is arranged at the bottom of the lifting support. The preparation method comprises the steps of material filling, single crystal growth and collaborative cooling. Wherein in the collaborative cooling stage, a bottom support heater is started to be heated to be matched with the bottom temperature of the crystal ingot, and then the bottom support heater and a furnace cavity heater are synchronously cooled. According to the method, auxiliary heating and synchronous slow cooling are performed on the bottom of the crystal ingot at the cooling stage after crystal growth is finished, so that thermal stress accumulation at the bottom and in the crystal ingot is effectively relieved, crystal cracking is remarkably inhibited, and the structural integrity and the yield of the tellurium-cadmium compound single crystal are improved.

Description

Technical Field

[0001] This invention belongs to the field of growth apparatus and preparation technology of cadmium telluride single crystals, specifically relating to a THM crystal growth apparatus and a method for preparing cadmium telluride crystals with low cracking rate. Background Technology

[0002] Cd 1-x Zn x Te crystals, as an important type of semiconductor crystal material, occupy an irreplaceable core position in high-end fields such as medical CT imaging, nuclear radiation monitoring, and astrophysical exploration due to their suitable bandgap, excellent carrier mobility-lifetime product, and outstanding X-ray and gamma-ray absorption coefficients. They are key to promoting the development of related fields towards higher resolution and higher sensitivity.

[0003] Among numerous crystal growth methods, the moving heater method (THM method) is one of the mainstream technologies for the large-scale preparation of cadmium telluride crystals. Compared with crystal growth techniques such as vertical gradient solidification (VGF) and vertical Bridgman (VB) methods, the growth temperature of the THM method is significantly lower. This helps to reduce thermal defects caused by high temperatures, thus theoretically enabling the production of crystal materials with lower intrinsic point defect density and higher purity. Simultaneously, by precisely controlling the melt zone migration process, the uniformity of compositional distribution within the crystal can be significantly optimized, effectively improving the compositional segregation problems that easily occur in the VGF and VB methods. Therefore, it is widely used in the industrial production of high-performance cadmium zinc telluride and cadmium telluride crystals.

[0004] Despite the numerous advantages of the THM method, cadmium telluride crystals, with their face-centered cubic structure, are extremely sensitive to growth and post-processing conditions. Their atomic arrangement is highly susceptible to defects caused by factors such as temperature distribution and stress release, severely hindering performance improvement and industrial application. The cooling stage after crystal growth is a critical period for crack initiation and propagation. Due to the low thermal conductivity and brittleness of cadmium telluride crystals, the cooling stage easily leads to defects such as bottom cracking, internal cracks, and grain boundary propagation. These defects not only directly damage the integrity of the crystal structure, obstructing carrier transport paths and significantly reducing electrical performance and detection sensitivity, but also drastically reduce the yield of intact single-crystal blocks in subsequent wafer-level processing such as cutting and grinding. A large number of ingots are discarded or downgraded due to bottom cracking and other defects, causing a sharp increase in raw material, energy, and processing costs, severely limiting the large-scale adoption of cadmium telluride crystals in various fields.

[0005] In summary, although existing THM crystal growth technology has advantages in principle, it is still plagued by problems such as thermal stress-induced cracking when actually preparing crystals such as zinc cadmium telluride and cadmium telluride. This limits the improvement of crystal structure integrity, the increase in product yield, and the reduction of production costs. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a THM crystal growth apparatus and a method for preparing cadmium telluride crystals with low cracking rate. The purpose of this invention is to solve the technical problem of easy cracking during the cooling stage of THM-grown cadmium telluride crystals, thereby providing a technical foundation for the reliable preparation of high-quality, high-yield cadmium telluride single crystals.

[0007] The first aspect of this invention is to provide a THM crystal growth apparatus, including a furnace body, a vertically arranged furnace cavity inside the furnace body, a furnace cavity heater arranged circumferentially around the inner side of the furnace cavity, a liftable lifting support disposed inside the furnace cavity, a driving device connected to the bottom of the lifting support for driving it to move vertically, a quartz crucible for containing crystal growth raw materials on the top of the lifting support, an upward-opening groove on the top of the lifting support, the inner wall contour of the groove being adapted to the bottom contour of the quartz crucible, a flat heating module disposed at the bottom of the groove, and the heating module being electrically connected to an external temperature control system.

[0008] As a further optimization of the aforementioned THM crystal growth apparatus, the heating module includes an upper insulation layer, a bottom support heater, and a lower insulation layer stacked sequentially from top to bottom. Both the upper and lower insulation layers are high-temperature resistant insulation plates that can slowly transfer heat. The bottom support heater is electrically connected to an external temperature control system and is used to start and heat up to a preset value that matches the temperature at the bottom of the crystal ingot during the cooling stage after crystal growth is completed, and then cool down synchronously with the furnace chamber heater.

[0009] As a further optimization of the above-mentioned THM crystal growth apparatus, the end of the bottom support heater is electrically connected to an external lead wire, and the bottom of the lifting support is connected to a support rod. The support rod has a channel inside for the external lead wire to pass through, and the external lead wire extends to the outside of the furnace body through the channel.

[0010] As a further optimization of the aforementioned THM crystal growth device, the heat insulation board is made of aluminum silicate fiberboard.

[0011] As a further optimization of the above-mentioned THM crystal growth apparatus, the depth of the slot is not less than 15 mm; more preferably, the depth of the slot is not less than 20 mm.

[0012] As a further optimization of the above-mentioned THM crystal growth device, the bottom heater is a heating wire disc formed by winding high-temperature resistant metal resistance wire into an integral disc shape or a flat electric heater.

[0013] As a further optimization of the aforementioned THM crystal growth apparatus, the inner wall of the quartz crucible is carbonized.

[0014] As a further optimization of the above-mentioned THM crystal growth apparatus, the insulation plates used in the upper and lower insulation layers have a thickness in the range of 5-25 mm and a thermal conductivity in the range of 0.08-0.32 W / (m·K), more preferably 0.1-0.3 W / (m·K).

[0015] A second aspect of the present invention provides a method for preparing cadmium telluride crystals with low cracking rate, using the above-mentioned THM crystal growth apparatus, comprising the following steps: S1. Material Preparation and Loading: Prepare the raw materials required for cadmium telluride crystal growth, including the alloy material to form the initial melting zone and the polycrystalline material as the solute source; the alloy material consists of tellurium solvent and cadmium telluride solute, and the polycrystalline material is cadmium telluride polycrystalline material; load the alloy material and polycrystalline material into the quartz crucible in a bottom-up order, and evacuate and seal the quartz crucible; the general chemical formula of cadmium telluride satisfies Cd 1-x Zn x Te, where 0 ≤ x ≤ 0.3; S2. Single crystal growth: The packaged quartz crucible is placed in the groove of the lifting support. An axial temperature gradient field is established in the furnace cavity through the furnace cavity heater. The lifting support is controlled to move the quartz crucible down at a preset rate, so that the raw material forms a melting zone and migrates along the axial direction to achieve the directional growth of cadmium telluride single crystal. S3. Synergistic Cooling: After the single crystal growth is completed, during the cooling stage, the bottom support heater in the heating module is started and its temperature is controlled to rise to a preset temperature that matches the temperature of the bottom of the ingot. Then, the furnace chamber heater and the bottom support heater are controlled to cool down to room temperature synchronously.

[0016] As a further optimization of the above method, the specific process of step S3, coordinated cooling, is as follows: the furnace chamber heater is controlled to start cooling at a first cooling rate, and the temperature field is kept constant when the temperature at the bottom of the ingot drops to a preset temperature within the range of 350-450℃; the bottom support heater is started and controlled to heat at a preset heating rate so that the temperature of the support area reaches the target temperature consistent with the temperature at the bottom of the ingot; subsequently, the furnace chamber heater and the bottom support heater are controlled to cool down synchronously to room temperature at a second cooling rate; wherein, the second cooling rate is equal to or slower than the first cooling rate.

[0017] Beneficial effects The THM crystal growth apparatus provided by this invention, through the integration of a liftable bottom heating support structure and a unique heat insulation-heating-heat insulation sandwich design, achieves precise matching and uniform control of the temperature field at the bottom of the ingot throughout the entire crystal growth process, especially during the cooling stage. This not only does not affect the stability of the melt zone migration and the continuity of crystal directional crystallization during the growth process, but also effectively alleviates the accumulation of thermal stress at the bottom and inside of the ingot, significantly improving the integrity and quality of the ingot. It avoids the common ingot bottom cracking defects in traditional methods, providing a new solution for the preparation of high-quality cadmium zinc telluride, cadmium telluride, and other single crystals. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the crystal growth apparatus of the present invention.

[0019] Figure 2 This is a schematic diagram of the base structure.

[0020] Figure 3 This is a cross-sectional view of the crystal obtained in Example 1.

[0021] Figure 4 This is a cross-sectional view of the crystal prepared in Comparative Example 1.

[0022] In the diagram, 1. Quartz crucible; 2. Furnace cavity heater; 3. Lifting support; 4. Support groove; 5. Alumina silicate fiberboard; 6. Bottom support heater; 7. External lead wire; 8. Support rod. Detailed Implementation

[0023] like Figure 1 and Figure 2 The diagram shows a THM crystal growth apparatus that can be used to grow cadmium zinc telluride and cadmium telluride single crystals. The apparatus has a furnace body with a vertically arranged furnace cavity inside. A furnace cavity heater 2 is arranged circumferentially around the inner side of the furnace cavity. A liftable lifting support 3 is also installed inside the furnace cavity. The bottom of the lifting support 3 is connected to a drive device that drives it to move vertically. A quartz crucible 1 is placed on top of the lifting support 3 to hold the crystal growth raw materials.

[0024] Quartz crucible 1 is made of high-purity quartz material, and its inner wall is carbonized to effectively prevent chemical reactions between the crystal growth material and the quartz material. Quartz crucible 1 has a cylindrical structure, and its inner diameter is compatible with the conventional material loading amount. Quartz crucible 1 has a certain pressure resistance. Before crystal growth, the inside of quartz crucible 1 is evacuated, and its open end is sealed using an oxyhydrogen flame, creating a high-vacuum, sealed space inside the crucible. This provides an oxygen-free and impurity-free clean environment for crystal growth. Quartz crucible 1 is placed on lifting support 3 and moves axially synchronously with lifting support 3, allowing the material inside quartz crucible 1 to sequentially pass through the high-temperature and low-temperature zones of the furnace cavity, achieving directional migration of the molten zone.

[0025] The furnace cavity heater 2 is fixedly installed in the middle region of the furnace body in a ring-shaped structure and is electrically connected to an external temperature control system. The furnace cavity heater 2 is used to construct the axial temperature gradient field required for THM crystal growth. This temperature gradient field includes an upper high-temperature zone, a lower low-temperature zone, and a gradient temperature zone in between. This temperature gradient field provides suitable temperature conditions for the melting of the alloy raw material to form a molten zone and for the directional crystallization. In some preferred embodiments, the high-temperature zone temperature is set at 900±50℃, the low-temperature zone temperature at 500±50℃, and the axial temperature gradient is controlled at 15±3K / cm.

[0026] The lifting tray 3 integrates support, movement, and bottom heating functions. Made of high-temperature resistant quartz material, its bottom is connected to a support rod 8. The end of the support rod 8 furthest from the lifting tray 3 is connected to the furnace body's drive mechanism, thereby driving the lifting tray 3 and the quartz crucible 1 mounted on it to rise and fall according to a preset direction and speed. The top of the lifting tray 3 has an upward-opening cylindrical groove 4. The inner contour of the groove 4 matches the bottom contour of the quartz crucible 1, and the depth of the groove 4 is preferably not less than 20mm to meet the stability requirements of the quartz crucible 1.

[0027] A flat heating module is installed at the bottom of the tray 4. The heating module preferably consists of two layers of aluminosilicate fiberboard 5 and a bottom support heater 6 sandwiched between the two layers. The lower layer of aluminosilicate fiberboard 5 is laid on the bottom end face of the tray 4, and the upper layer covers the upper surface of the bottom support heater 6. The bottom support heater 6 is an electrically heated component; when energized, it generates heat and transfers it to the two layers of aluminosilicate fiberboard 5. The lower layer of aluminosilicate fiberboard 5 reduces heat loss to the support rod 8 and the lower part of the furnace body, improving the energy efficiency of bottom heating; the upper layer of aluminosilicate fiberboard 5 supports the crucible, making the temperature distribution at the bottom of the quartz crucible 1 more uniform. Furthermore, the ultra-high temperature resistance, good chemical stability, flexibility, and shock resistance of the aluminosilicate fiberboard 5 make it a preferred material for the upper and lower heat release layers of the heating module.

[0028] The bottom support heater 6 can be made of high-temperature resistant platinum-rhodium alloy resistance wire, which is uniformly coiled in a serpentine or spiral shape, and the overall size of the coiled wire is adapted to the bottom size of the support groove 4. Alternatively, the bottom support heater 6 can also be a flat plate electric heating component. The bottom support heater 6 is the heat source for the flat plate heating module. During the cooling stage after crystal growth, it receives a signal from the external temperature control system and heats up to a temperature that matches the temperature field of the furnace body. Then, it cools down synchronously with the furnace chamber heater 2, which greatly alleviates the accumulation of thermal stress at the bottom of the ingot and prevents cracking at the bottom of the ingot.

[0029] The bottom support heater 6 is electrically connected to an external lead wire 7 at its end. The external lead wire 7 is made of high-temperature resistant insulated wire and is wrapped with a quartz fiber insulation layer. The support rod 8 is cylindrical, with a hollow channel running through its middle along the axial direction. The end of the external lead wire 7 away from the bottom support heater 6 passes sequentially through the through hole at the bottom of the support groove 4 and the hollow channel of the support rod 8, extending to the outside of the furnace body and connecting to the external temperature control system. This wiring method avoids interference of the external lead wire 7 with the lifting movement of the lifting support 3, and also allows the external lead wire 7 to pass through the relatively cool lower part of the furnace body, extending its service life.

[0030] The heating module of the lifting tray can be assembled in the following order: First, lay a layer of aluminum silicate fiber board 5 flat on the bottom end face of the tray 4. Then, install the bottom tray heater 6 on the upper surface of the aluminum silicate fiber board 5 and complete the connection between the bottom tray heater 6 and the external lead wire 7. After that, lay another layer of aluminum silicate fiber board 5 on the upper surface of the bottom tray heater 6 to complete the assembly of the heating module. Finally, fix the support rod 8 to the bottom of the tray 4 and lead the external lead wire 7 out through the hollow channel in the middle of the support rod 8.

[0031] The THM crystal growth apparatus is used as follows: During the crystal growth stage, the furnace chamber heater 2 constructs a stable axial temperature gradient field, and the driving device drives the lifting support 3 to slowly move down, causing the molten zone in the quartz crucible 1 to migrate in a directional manner, thereby achieving continuous growth of single crystals; During the cooling stage, the crystal growth has ended, the bottom support heater 6 is started and heated to a preset value that matches the temperature of the bottom of the crystal ingot, and then it is slowly cooled down to room temperature in sync with the furnace chamber heater 2, ensuring a uniform temperature field at the bottom of the crystal ingot and effectively suppressing thermal stress cracking at the bottom and inside of the crystal ingot.

[0032] Example 1 This embodiment is based on the aforementioned THM crystal growth apparatus for Cd production. 0.9 Zn 0.1 Te single crystal growth process.

[0033] Step 1: Pre-synthesizing solid alloy material Weigh out 700g of tellurium (Te) raw material and Cd 0.9 Zn 0.1 300g of Te raw material was mixed to prepare a total mass of 1kg of Te and Cd. 0.9 Zn 0.1 The alloy of Te is used as the matrix for the initial melting zone; 2.5 kg of Cd is also weighed. 0.9 Zn 0.1 Te polycrystalline material was used as a solute replenishment source during crystal growth. A quartz crucible 1 with carbonized inner walls was selected as the pre-synthesis container to avoid chemical reactions between the raw material and the quartz material. The aforementioned Te raw material was then mixed with Cd... 0.9 Zn 0.1Te raw material is loaded into the quartz crucible 1, heated to 700℃ and held at that temperature until Te is completely melted into a liquid solvent, Cd 0.9 Zn 0.1 The Te raw material is fully dissolved in liquid Te to form a liquid unsaturated alloy with uniform composition. Then, heating is stopped, and the crucible is allowed to cool to room temperature with the furnace, and the liquid alloy solidifies into a solid alloy.

[0034] Step 2: Material filling and vacuum sealing Take a quartz crucible 1 with its inner wall treated by carbonization, and fill it with materials in the following order from bottom to top: place the solid alloy material prepared in the previous steps at the bottom, and fill the top layer with Cd. 0.9 Zn 0.1 For Te polycrystalline material, connect the filled quartz crucible 1 to the vacuum system and evacuate to a vacuum level of <10⁻. 4 Pa is used to remove air and impurity gases from inside the crucible. Then, the open end of the quartz crucible 1 is sealed with an oxyhydrogen flame to form an oxygen-free and impurity-free high-vacuum sealed growth environment.

[0035] Step 3: Single crystal growth The sealed quartz crucible 1 is smoothly placed into the slot 4 at the top of the lifting support 3. The furnace drive device is activated, and the position of the lifting support 3 is adjusted so that the solid alloy material at the bottom of the quartz crucible 1 is within the high-temperature zone of the furnace heater 2. The external temperature control system is activated, and the temperature field parameters of the furnace heater 2 are set, with the high-temperature zone temperature at 900℃, the low-temperature zone temperature at 500℃, and the axial temperature gradient inside the furnace controlled at 15K / cm. Then, the heating program is started, controlling the furnace heater 2 to heat up at a rate of 30℃ / min to the set temperature field parameters. After reaching the target temperature, it is held at that temperature for 48 hours. After the holding time is completed, the drive device is activated, controlling the lifting support 3 to slowly move downward at a rate of 3mm / day, causing the quartz crucible 1 to move downward synchronously. Utilizing the axial temperature gradient field constructed by the furnace heater 2, the liquid molten zone is driven to migrate axially. During the migration of the molten zone, Cd 0.9 Zn 0.1 Te solute precipitates directionally at the low-temperature end of the molten zone and grows into a single crystal. The polycrystalline material on top gradually dissolves into the liquid Te as the molten zone moves, continuously replenishing the solute and ensuring continuous growth of the single crystal. The crystal growth process ends when the liquid Te solvent has completely drained to the end of the ingot.

[0036] Step 4: Cooling down The furnace chamber heater 2 is controlled to cool down at a rate of 25°C / day. Once the temperature at the bottom of the ingot reaches 400°C, it is kept constant. Meanwhile, the bottom support heater 6 is activated and heated to 400°C at a rate of 30°C / h to match the temperature of the bottom support heater with that of the ingot. Then, the furnace chamber heater 2 and the bottom support heater 6 are simultaneously cooled to room temperature at a rate of 25°C / day to alleviate thermal stress accumulation at the bottom of the ingot and prevent cracking. After the furnace body has completely cooled, the quartz crucible 1 is removed, the crucible seal is broken, and Cd is obtained. 0.9 Zn 0.1 Te crystal ingot.

[0037] Comparative Example 1 This comparative example is based on the same THM crystal growth apparatus as Example 1, uses the same raw materials as Example 1, and the operation process and process parameters of steps 1 to 3 are the same as those of Example 1.

[0038] The only difference between this comparative example and Example 1 is the cooling operation in step 4. Specifically, the furnace chamber heater 2 is controlled to cool directly to room temperature at a rate of 25°C / day, and the bottom support heater 6 is not activated throughout the process. After the furnace body has completely cooled, the quartz crucible 1 is removed, the crucible seal is broken, and Cd is obtained. 0.9 Zn 0.1 Te crystal ingot.

[0039] Results and Analysis Experimental results are as follows Figure 3 and Figure 4 As shown, Cd grown in Example 1 0.9 Zn 0.1 Te crystal ingot, with no cracks on the bottom cut surface; Comparative Example 1: Cd grown in... 0.9 Zn 0.1 Te crystal ingots exhibit bottom surface cracking. A flat heating module, consisting of an aluminosilicate fiber plate 5 and a bottom heater 6, is installed within the groove 4 of the lifting support 3. This module, with its "insulation layer-heating layer-insulation layer" sandwich structure, plays a crucial role in the cooling stage after crystal growth. The upper aluminosilicate fiber plate 5 slows heat upwards, resulting in more uniform heating of the bottom of the quartz crucible 1; the lower aluminosilicate fiber plate 5 reduces heat loss to the support structure. This structure allows the bottom heater 6 to quickly and evenly transfer heat to the bottom of the ingot after startup, matching the temperature at the bottom of the ingot with the lower part of the furnace cavity temperature field, achieving more uniform synchronous slow cooling. Consequently, the axial and radial temperature gradients at the bottom of the ingot are significantly reduced, suppressing thermal stress and preventing cracking at the bottom of the ingot.

[0040] The above embodiments are exemplary and are intended to illustrate the technical concept and features of the present invention, so that those skilled in the art can understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A THM crystal growth apparatus, characterized in that: The furnace includes a furnace body, inside which is a vertically arranged furnace cavity. A furnace cavity heater (2) is arranged circumferentially around the inner side of the furnace cavity. A liftable lifting support (3) is arranged inside the furnace cavity. The bottom of the lifting support (3) is connected to a drive device that drives it to move vertically. The top of the lifting support (3) carries a quartz crucible (1) for containing crystal growth raw materials. The top of the lifting support (3) has an upward-opening groove (4). The inner wall contour of the groove (4) is adapted to the bottom contour of the quartz crucible (1). A flat heating module is arranged at the bottom of the groove (4). The heating module is electrically connected to an external temperature control system.

2. The THM crystal growth apparatus according to claim 1, characterized in that: The heating module includes an upper heat insulation layer, a bottom support heater (6) and a lower heat insulation layer stacked from top to bottom. The upper heat insulation layer and the lower heat insulation layer are both heat insulation plates (5) that are resistant to high temperature and can slowly transfer heat. The bottom support heater (6) is electrically connected to an external temperature control system and is used to start and heat up to a preset value that matches the temperature at the bottom of the crystal ingot during the cooling stage after the crystal growth is completed. Then it cools down synchronously with the furnace chamber heater (2).

3. The THM crystal growth apparatus according to claim 2, characterized in that: The bottom heating element (6) is electrically connected to an external lead wire (7) at its end. The bottom of the lifting support (3) is connected to a support rod (8). The support rod (8) has a channel inside for the external lead wire (7) to pass through. The external lead wire (7) passes through the channel and extends to the outside of the furnace body.

4. The THM crystal growth apparatus according to claim 2, characterized in that: The heat insulation board (5) is an aluminum silicate fiberboard.

5. The THM crystal growth apparatus according to any one of claims 2-4, characterized in that: The depth of the bracket (4) is not less than 15mm.

6. The THM crystal growth apparatus according to claim 5, characterized in that: The base heater (6) is a heating wire disc or a flat electric heater formed by winding high-temperature resistant metal resistance wire.

7. The THM crystal growth apparatus according to claim 5, characterized in that: The inner wall of the quartz crucible (1) is carbonized.

8. The THM crystal growth apparatus according to claim 5, characterized in that: The insulation boards (5) used in the upper and lower insulation layers have a thickness of 5-25 mm and a thermal conductivity of 0.08-0.32 W / (m·K).

9. A method for preparing cadmium telluride crystals with low cracking rate, characterized in that, The THM crystal growth apparatus as described in any one of claims 2-8 includes the following steps: S1. Material Preparation and Loading: Prepare the raw materials required for the growth of cadmium telluride crystals, including alloy material to form the initial melting zone and polycrystalline material as a solute source; the alloy material is composed of tellurium (Te) solvent and cadmium telluride solute, and the polycrystalline material is cadmium telluride polycrystalline material; load the alloy material and polycrystalline material into the quartz crucible (1) in a bottom-up order, and evacuate and seal the quartz crucible (1); the chemical formula of the cadmium telluride satisfies Cd 1-x Zn x Te, where 0 ≤ x ≤ 0.3; S2, Single crystal growth: The encapsulated quartz crucible (1) is placed in the slot (4) of the lifting support (3). An axial temperature gradient field is established in the furnace cavity through the furnace cavity heater (2), and the lifting support (3) is controlled to drive the quartz crucible (1) to move down at a preset rate, so that the raw material forms a melting zone and migrates along the axial direction, thereby realizing the directional growth of cadmium telluride single crystal; S3. Synergistic cooling: After the single crystal growth is completed, during the cooling stage, the bottom support heater (6) in the heating module is started and its temperature is controlled to rise to a preset temperature that matches the temperature of the bottom of the crystal ingot. Then, the furnace cavity heater (2) and the bottom support heater (6) are controlled to cool down to room temperature synchronously.

10. The method for preparing low-cracking-rate cadmium telluride crystals according to claim 9, characterized in that, The coordinated cooling process described in step S3 is as follows: the furnace chamber heater (2) is controlled to start cooling at a first cooling rate, and the temperature field is kept constant when the temperature at the bottom of the ingot drops to a preset temperature in the range of 350-450℃; the bottom support heater (6) is started and controlled to heat at a preset heating rate so that the temperature of the support groove (4) reaches the target temperature consistent with the temperature at the bottom of the ingot; then, the furnace chamber heater (2) and the bottom support heater (6) are controlled to cool down synchronously to room temperature at a second cooling rate; wherein, the second cooling rate is equal to or slower than the first cooling rate.

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