A method for controlling the level of dislocations in a germanium single crystal

Abstract

The application provides a germanium single crystal dislocation level control method, and belongs to the technical field of germanium single crystal dislocation control. The method comprises the following steps: preparing a plurality of germanium single crystals without dislocations; placing the plurality of germanium single crystals in layers from top to bottom in a mold, and ensuring that the germanium single crystals have an installation spacing from the inner wall of the mold; placing the mold in a furnace body, and ensuring that the mold is located at the center position of the heater in the furnace body; evacuating the furnace body, filling inert gas into the furnace body to a normal pressure state, starting the heater, and controlling the furnace body to experience a low-temperature warming-up stage, a medium-temperature warming-up stage, a heat preservation stage and a stepwise cooling-down stage, so that the germanium single crystals have a certain dislocation density; and finally taking out the plurality of germanium single crystals, and performing dislocation testing on the germanium single crystals to obtain test pieces. The germanium single crystal dislocation level control method provided by the application realizes accurate control of the dislocation density of the germanium single crystal, and improves the preparation efficiency.

Description

Technical Field

[0001] This invention belongs to the field of germanium single crystal dislocation control technology, and more specifically, relates to a method for controlling the dislocation level in germanium single crystals. Background Technology

[0002] Germanium single crystals, with their diamond structure, hold an irreplaceable position in infrared optics, detection, and solar cell applications. Dislocations are a typical defect in semiconductor materials, directly affecting their electrical and processing properties, thus influencing their final use. Excessive dislocation levels reduce crystal processing performance, making them prone to breakage, and also degrade their electrical properties. Dislocation-free germanium single crystals contain numerous point defects and vacancies, affecting their electronic properties, molecular doping effects, and electron transport characteristics. The presence of dislocations facilitates the absorption of vacancies. In detector applications, the presence of dislocations severely impacts carrier collection efficiency. Therefore, detector-grade high-purity germanium materials have very strict requirements for dislocation density; both excessively high and low dislocation densities degrade the detector's energy resolution. Dislocations form intermediate energy levels in the band gap, causing photogenerated carriers to be trapped, leading to decreased charge collection efficiency, increased leakage current, and reduced energy resolution. When the dislocation density of a crystal exceeds 5 × 10³ cm⁻², the detector's energy resolution deteriorates significantly. Furthermore, dislocation-free high-purity germanium crystals grown in a hydrogen atmosphere cannot be used for detector manufacturing because hydrogen vacancies exist within the crystal, acting as strong charge trapping centers. Dislocations can isolate hydrogen vacancies and eliminate charge trapping. When the dislocation density of the crystal is greater than 100 cm⁻², the low concentration has almost no impact on detector performance. Therefore, the dislocation density of detector-grade high-purity germanium crystals should be between 1 × 10² and 5 × 10³ cm⁻². Thus, obtaining dislocations while simultaneously controlling and adjusting their levels is crucial for detector-grade high-purity germanium single crystals.

[0003] The conventional method for controlling the dislocation level of germanium single crystals involves designing a suitable temperature gradient for growth within the Czochralski furnace's thermal field, including heaters, insulation tanks, flow guides, and the upper insulation structure. Dislocations are then eliminated using a seed crystal necking technique. Following shoulder formation, shoulder rotation, equal diameter setting, and tailing processes, a suitable germanium single crystal is obtained. However, while dislocation-free germanium single crystals are readily obtained using this method, germanium single crystals with low dislocation densities are difficult to achieve. After eliminating native dislocations in the seed crystal through seed crystal necking, setting a suitable thermal field so that the stress level in the crystal during growth is less than the edge strength required to generate dislocations results in dislocation-free germanium single crystals. However, if the stress level in the crystal exceeds the edge strength required to generate dislocations, dislocations will be generated and multiply rapidly through climb or slip, leading to defective crystals. This method results in low germanium single crystal production efficiency and makes it impossible to produce germanium single crystals with varying dislocation densities. Summary of the Invention

[0004] The purpose of this invention is to provide a method for controlling the dislocation level of germanium single crystals, so as to solve the technical problems of low efficiency and inability to produce germanium single crystals with different dislocation densities in the existing technology.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: to provide a method for controlling the dislocation level of a germanium single crystal, comprising:

[0006] S1: Prepare multiple dislocation-free germanium single crystals;

[0007] S2: Multiple germanium single crystals are placed in layers inside the mold, with an installation gap between the germanium single crystals and the inner wall of the mold;

[0008] S3: Place the mold inside the furnace, with the mold located at the center of the heater inside the furnace;

[0009] S4: Evacuate the furnace body and fill it with inert gas to atmospheric pressure, setting the inert gas flow rate to 5-15 slm;

[0010] S5: Start the heater and control the temperature inside the furnace as follows:

[0011] 1) Increase the temperature inside the furnace from room temperature to 400-450℃ at a rate of 1-8℃ / min;

[0012] 2) Increase the temperature inside the furnace to 650-700℃ at a rate of 0.5-3℃ / min;

[0013] 3) Maintain the temperature inside the furnace at 650-700℃ and keep it at this temperature for 0.5-3 hours;

[0014] 4) Reduce the temperature inside the furnace to 350-450℃ at a rate of 0.5-1.5℃ / h;

[0015] 5) Reduce the temperature inside the furnace to 150-250℃ at a rate of 0.5-3℃ / h;

[0016] 6) Reduce the temperature inside the furnace to room temperature at a rate of 1.5-4℃ / h;

[0017] S6: Take out multiple germanium single crystals and perform dislocation tests on the germanium single crystal cut test pieces.

[0018] In one possible implementation, in step S2, multiple annular supports arranged at intervals are installed on the mold, and the sum of the inner diameter and width of the annular supports is set to be greater than the outer diameter of the germanium single crystal; the multiple germanium single crystals are placed on the multiple annular supports respectively.

[0019] In one possible implementation, the heater in step S3 is arranged in a ring on the inner wall of the furnace body, and a lifting rod is installed at the bottom of the furnace body, with a tray installed on the lifting rod; when the mold is placed in the furnace body, the mold is placed on the tray; then the lifting rod is activated to drive the mold to the center position of the heater.

[0020] In one possible implementation, in step S2, the mold includes a plurality of sleeves stacked one on top of the other, and an annular support is installed inside each sleeve; the annular support includes a plurality of support blocks, which are fixedly installed on the inner wall of the sleeve and are evenly spaced along the circumference of the sleeve; a groove for supporting germanium single crystal is formed on each support block, and the grooves on the plurality of support blocks form a limiting groove for fitting and installing with the germanium single crystal.

[0021] In one possible implementation, in step S5, the temperature change inside the furnace is set as follows:

[0022] 1) The temperature inside the furnace is increased from room temperature to 420℃ at a rate of 6℃ / min;

[0023] 2) Increase the temperature inside the furnace to 670℃ at a rate of 1℃ / min;

[0024] 3) Maintain the furnace temperature at 670℃ and keep it at that temperature for 2 hours;

[0025] 4) Reduce the temperature inside the furnace to 400℃ at a rate of 0.8℃ / h;

[0026] 5) Reduce the temperature inside the furnace to 200℃ at a rate of 1℃ / h;

[0027] 6) Reduce the temperature inside the furnace to room temperature at a rate of 2℃ / h.

[0028] In one possible implementation, in step S1, serial numbers are marked on multiple dislocation-free germanium single crystals; in step S2, they are placed into the mold sequentially from bottom to top or from top to bottom according to the serial numbers.

[0029] In one possible implementation, in step S1, the head and tail of the dislocation-free germanium single crystal are removed, and a cylindrical single crystal segment of the desired product size is obtained by rolling.

[0030] In one possible implementation, in step S6, test pieces are cut from the head and tail of the extracted germanium single crystal for dislocation testing, and the thickness of the test pieces is 5 mm.

[0031] In one possible implementation, in step S4, the inert gas is argon.

[0032] The beneficial effects of the germanium single crystal dislocation level control method provided by the present invention are as follows: Compared with the prior art, the germanium single crystal dislocation level control method of the present invention first uses traditional technology to prepare dislocation-free germanium single crystals, and obtains initial dislocation-free germanium single crystals by strictly controlling the thermal field temperature gradient and combining crystal necking process; this step provides a pure germanium single crystal substrate for subsequent dislocation control, avoiding interference of native dislocations on subsequent processes.

[0033] Then, multiple dislocation-free germanium single crystals are layered and placed in a mold, with an installation gap between the germanium single crystals and the inner wall of the mold. The layered layout ensures that the germanium single crystals are heated evenly during the heat treatment process, avoids uneven heat conduction caused by close contact, and reserves space for thermal expansion of the germanium single crystals, reducing mechanical stress damage to the germanium single crystals.

[0034] Then, the mold is precisely placed at the center of the furnace heater to ensure that the germanium single crystal is at the center of thermal field symmetry, avoiding local overheating or temperature unevenness caused by offset, and laying the foundation for the stability of subsequent temperature control processes.

[0035] Next, the furnace body is evacuated and then filled with inert gas to atmospheric pressure, with the gas flow rate controlled at 5-15 slm. The inert gas environment can effectively prevent germanium single crystals from oxidizing at high temperatures, and the stable airflow helps to achieve a uniform temperature field distribution inside the furnace, avoiding the impact of local atmosphere fluctuations on the performance of germanium single crystals.

[0036] The next step is to start the heater and control it to operate at a set level to control the temperature inside the furnace. Specifically:

[0037] Low-temperature heating stage: The temperature is increased from room temperature to 400-450℃ at a rate of 1-8℃ / min. The slow heating allows the germanium single crystal to gradually adapt to the temperature change, reducing the sudden dislocation multiplication caused by the sudden increase in thermal stress.

[0038] Medium-temperature heating stage: Heating to 650-700℃ at a rate of 0.5-3℃ / min. In this stage, the accumulation of thermal stress is further controlled by a lower heating rate, creating conditions for the orderly induction of dislocations.

[0039] Heat preservation stage: Heat at 650-700℃ for 0.5-3 hours to allow the atoms inside the germanium single crystal to diffuse fully, and dislocations to begin to germinate and slowly multiply under thermal activation, while avoiding excessive accumulation of dislocations due to prolonged high temperature.

[0040] The cooling process involves several stages: first, the temperature is reduced to 350-450℃ at a rate of 0.5-1.5℃ / h; then to 150-250℃ at a rate of 0.5-3℃ / h; and finally to room temperature at a rate of 1.5-4℃ / h. This multi-gradient slow cooling process precisely controls the stress release rate during the cooling of germanium single crystals, ensuring a stable increase in dislocation density within the target range and preventing stress concentration and explosive dislocation proliferation caused by rapid cooling.

[0041] Finally, after removing the germanium single crystal from the mold, a test piece is cut out and dislocation density is tested using methods such as etching to ensure that the final product meets the requirements for detector-grade materials.

[0042] In this way, the dislocation density of germanium single crystals is precisely controlled by heat treatment-induced dislocations; and the processing efficiency is improved by arranging multiple germanium single crystals in layers within a mold. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a schematic diagram of the working state of the germanium single crystal dislocation level control method provided in the embodiment of the present invention;

[0045] Figure 2 This is a schematic diagram showing the connection between the mold and the germanium single crystal provided in an embodiment of the present invention;

[0046] Figure 3 A top view of the mold provided in an embodiment of the present invention.

[0047] The following are the labeling elements in the figure:

[0048] 10. Furnace body; 11. Receiving cavity; 12. Heater; 20. Lifting rod; 21. Tray; 30. Mold; 31. Installation spacing; 32. Sleeve; 40. Annular support; 41. Support block; 42. Groove; 50. Limiting connector; 51. Rotating hole; 52. Connecting shaft; 53. Square hole; 54. Square shaft; 60. Germanium single crystal. Detailed Implementation

[0049] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0050] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0051] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0052] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0053] Please see Figure 1 The present invention will now describe the method for controlling the dislocation level in a germanium single crystal. A method for controlling the dislocation level in a germanium single crystal includes:

[0054] S1: Prepare multiple dislocation-free germanium single crystals 60;

[0055] S2: Multiple germanium single crystals 60 are placed in the mold 30 in layers, and there is an installation gap 31 between the germanium single crystals 60 and the inner wall of the mold 30;

[0056] S3: Place the mold 30 inside the furnace body 10, with the mold 30 located at the center of the heater 12 in the furnace body 10;

[0057] S4: Evacuate the furnace body 10 and fill it with inert gas to atmospheric pressure, setting the inert gas flow rate to 5-15 slm;

[0058] S5: Start heater 12 and control the temperature inside furnace 10 as follows:

[0059] 1) The temperature inside the furnace body 10 is raised from room temperature to 400-450℃ at a rate of 1-8℃ / min;

[0060] 2) Increase the temperature inside the furnace body 10 to 650-700℃ at a rate of 0.5-3℃ / min;

[0061] 3) Maintain the temperature inside the furnace body 10 at 650-700℃ and keep it at this temperature for 0.5-3 hours;

[0062] 4) Reduce the temperature inside the furnace body 10 to 350-450℃ at a rate of 0.5-1.5℃ / h;

[0063] 5) Reduce the temperature inside the furnace body 10 to 150-250℃ at a rate of 0.5-3℃ / h;

[0064] 6) Reduce the temperature inside the furnace body 10 to room temperature at a rate of 1.5-4℃ / h;

[0065] S6: Take out multiple germanium single crystals 60 and cut test pieces of germanium single crystals 60 to perform dislocation tests.

[0066] The dislocation level control method for germanium single crystals provided by this invention, compared with the prior art, firstly uses traditional technology to prepare dislocation-free germanium single crystal 60. Based on strict control of the thermal field temperature gradient and combined with the crystal necking process, an initial dislocation-free germanium single crystal 60 is obtained. This step provides a pure germanium single crystal 60 substrate for subsequent dislocation control, avoiding interference of native dislocations with subsequent processes.

[0067] Then, multiple dislocation-free germanium single crystals 60 are layered in the mold 30, with an installation gap 31 between the germanium single crystals 60 and the inner wall of the mold 30. The layered layout ensures that the germanium single crystals 60 are heated evenly during the heat treatment process, avoids uneven heat conduction caused by close contact, and reserves space for the thermal expansion of the germanium single crystals 60, reducing mechanical stress damage to the germanium single crystals 60.

[0068] Then, the mold 30 is precisely placed at the center of the heater 12 of the furnace body 10 to ensure that the germanium single crystal 60 is at the center of thermal field symmetry, avoiding local overheating or temperature unevenness caused by offset, and laying the foundation for the stability of subsequent temperature control process.

[0069] Next, the furnace body 10 is evacuated and then filled with inert gas to atmospheric pressure, with the gas flow rate controlled at 5-15 slm. The inert gas environment can effectively prevent germanium single crystal 60 from oxidizing at high temperatures, and the stable airflow helps to achieve a uniform distribution of the temperature field inside the furnace, avoiding the impact of local atmosphere fluctuations on the performance of germanium single crystal 60.

[0070] The next step is to start heater 12 and control it to operate at a set level to control the temperature inside furnace 10, specifically as follows:

[0071] Low-temperature heating stage: The temperature is raised from room temperature to 400-450℃ at a rate of 1-8℃ / min. The slow heating allows the germanium single crystal 60 to gradually adapt to the temperature change, reducing the sudden dislocation proliferation caused by the sudden increase in thermal stress.

[0072] Medium-temperature heating stage: Heating to 650-700℃ at a rate of 0.5-3℃ / min. In this stage, the accumulation of thermal stress is further controlled by a lower heating rate, creating conditions for the orderly induction of dislocations.

[0073] Heat preservation stage: Heat at 650-700℃ for 0.5-3 hours to allow the atoms inside germanium single crystal 60 to diffuse fully, and dislocations to begin to germinate and slowly multiply under thermal activation, while avoiding excessive accumulation of dislocations due to prolonged high temperature.

[0074] The cooling process involves several stages: first, the temperature is reduced to 350-450℃ at a rate of 0.5-1.5℃ / h; then to 150-250℃ at a rate of 0.5-3℃ / h; and finally to room temperature at a rate of 1.5-4℃ / h. This multi-gradient slow cooling process precisely controls the stress release rate during the cooling of germanium single crystal 60, ensuring a stable increase in dislocation density within the target range and preventing stress concentration and explosive dislocation proliferation caused by rapid cooling.

[0075] Finally, after removing the germanium single crystal 60 from mold 30, a test piece is cut out and dislocation density is tested by methods such as etching to ensure that the final product meets the requirements of detector-grade materials.

[0076] In this way, by inducing dislocations through heat treatment, the dislocation density of germanium single crystal 60 is precisely controlled; and by arranging multiple germanium single crystal 60 crystals in layers within the mold 30 for processing, the preparation efficiency is improved.

[0077] Taking two germanium single crystals 60 placed in mold 30 as an example, before placing them into mold 30, the two prepared germanium single crystals 60 are cleaned and labeled A and B respectively; germanium single crystal 60 A is placed on the upper layer and germanium single crystal 60 B is placed on the lower layer, and mold 30 is locked. Dislocation testing is performed on the test piece using the etching method. The test result shows that the dislocation level of product A is 800 cm. -1 ~1200cm -1The dislocation level of product B is 1100cm. -1 ~1600cm -1 .

[0078] The mold 30 is made of molybdenum or other materials with good thermal conductivity, high temperature resistance and chemical stability. The purpose of the mold 30 is twofold: first, to prevent the dislocation-free germanium single crystal 60 from being directly exposed to the heater 12, which would cause an excessive temperature difference between the surface temperature and the internal temperature of the single crystal, resulting in uneven stress distribution and dislocation proliferation; second, to place the single crystal in different temperature zones, which can adjust the dislocation range of each layer of germanium single crystal 60.

[0079] The furnace body 10 is a pit-type annealing furnace, the lifting rod 20 is a liftable crucible rod, and the tray 21 is a cured carbon felt tray. The furnace body 10 has a receiving cavity 11, in which the heater 12, the lifting rod 20, the tray 21, and the mold 30 are all located.

[0080] Please see Figures 1 to 3 In the specific implementation of step S2, multiple annular supports 40 spaced vertically are arranged within the mold 30, with the sum of the inner diameter and width of the supports greater than the outer diameter of the germanium single crystal 60, forming a layered support structure for the germanium single crystal 60. This method allows the germanium single crystal 60 to be stably placed on the annular supports 40, maintaining a specific distance from the inner wall of the mold 30 and from adjacent germanium single crystals 60, avoiding direct contact. The annular structure of the supports 40 evenly distributes the weight of the germanium single crystal 60, reducing contact stress concentration; the reserved installation gaps provide buffer space for the thermal expansion of the germanium single crystal 60 during heat treatment, while facilitating the flow of inert gas and heat transfer within the furnace, ensuring uniform heating of each germanium single crystal 60. This structure, through structured support, prevents the germanium single crystal 60 from shifting position due to gravity or thermal deformation, ensuring consistent stress distribution during dislocation induction; the spaced layout promotes thermal field uniformity, preventing uneven dislocation density caused by local overheating or contact conduction; simultaneously, the multi-layered support allows for the processing of multiple germanium single crystals 60 at a time, improving production efficiency.

[0081] Please see Figure 1In the specific implementation of step S3, an annular heater 12 is arranged around the inner wall of the furnace body 10, in conjunction with the furnace bottom lifting rod 20 and the tray 21 structure, to achieve precise thermal field positioning of the mold 30. The annular heater 12, through symmetrically distributed heating units, forms a uniform radial temperature field in the furnace, avoiding temperature gradient deviation caused by traditional unilateral heating; the lifting rod 20 drives the tray 21 to carry the mold 30 up and down, which can precisely adjust the position of the mold 30 in the axial thermal field, ensuring that it is strictly in the center of the heater 12. This position is the area with the best thermal field symmetry and the smallest temperature distribution uniformity error. The annular heating structure eliminates the thermal field blind zone, avoiding abnormal dislocation proliferation of germanium single crystal 60 due to local overheating or undercooling; the precise control capability of the lifting rod 20 ensures that each batch of molds 30 is in the same thermal field center position; and the tray 21 supports the mold 30 in a stable and reliable manner. Combined with the mechanical positioning accuracy of the lifting rod 20, it ensures a high degree of controllability of the heating conditions of germanium single crystal 60 during heat treatment.

[0082] Please see Figures 1 to 3 As a specific implementation of the dislocation level control method for germanium single crystals provided by the present invention, in the specific implementation of step S2, the mold 30 adopts a stacked sleeve 32 structure. Each sleeve 32 has uniformly arranged grooved support blocks 41 on its inner wall, forming a limiting groove that matches the outer diameter of the germanium single crystal 60. This design achieves layered independent support for the germanium single crystal 60 through modular sleeves 32. The uniform distribution of support blocks 41 can evenly bear the weight of the germanium single crystal 60, avoiding stress concentration caused by single-point contact. The grooves 42 precisely match the outer diameter of the germanium single crystal 60, fixing its position to prevent displacement and reserving a small installation gap to accommodate thermal expansion during heat treatment. Through this structure, the layered sleeve 32 structure achieves an orderly vertical arrangement of multiple germanium single crystals 60, significantly increasing the loading capacity of germanium single crystals 60 in a single heat treatment and improving production efficiency. Furthermore, the uniform circumferential support and limiting design ensure that the germanium single crystal 60 remains stable in a high-temperature environment, avoiding localized stress abnormalities or uneven heat conduction caused by positional changes.

[0083] The limiting connector 50 on the outer wall of the sleeve 32 achieves detachable connection between adjacent sleeves 32 through the cooperation of the upper rotating hole 51 and the lower connecting shaft 52. The rotating hole 51 includes a circular hole and a square hole 53 arranged in sequence. The connecting shaft 52 includes a circular shaft and a square shaft 54. The circular shaft is rotatably connected to the circular hole, and the square hole 53 is fitted with the square shaft 54. Through this structure, the square shaft 54 ​​on the rotating shaft is disengaged from the square hole 53. The two adjacent sleeves 32 can be opened by controlling relative rotation of the two sleeves 32 with the help of the circular hole and the circular shaft, which facilitates opening or closing the sleeves 32. When the square shaft 54 ​​on the upper sleeve 32 is inserted into the square hole 53, the two sleeves 32 are fixed.

[0084] In the specific implementation of step S5, the temperature change parameters within the furnace body 10 are further clarified, and dislocation induction and stress regulation are achieved through precise segmented temperature control. Specifically, the low-temperature heating stage increases the temperature to 420℃ at a rate of 6℃ / min, the medium-temperature heating stage increases the temperature slowly to 670℃ at a rate of 1℃ / min, the holding stage is maintained at 670℃ for 2 hours, and the step-down cooling stage uses a decreasing rate of 0.8℃ / h to 1℃ / h to 2℃ / h until the temperature reaches room temperature. The process involves several key steps: The low-temperature heating stage rapidly establishes a basic temperature environment while avoiding a sudden increase in thermal stress, preparing for the subsequent medium-temperature stage; the medium-temperature heating stage controls the thermal stress gradient through an extremely low heating rate, ensuring orderly dislocation germination rather than sudden multiplication during atomic diffusion; the holding stage provides sufficient time for dislocations to stably multiply to the lower limit of the target density range under thermal activation, avoiding insufficient dislocations due to short holding times or excessive aggregation due to excessive holding times; and the stepped cooling stage releases the internal stress of germanium single crystal 60 in stages from high temperature to room temperature, with each temperature gradient being less than the critical excitation stress for dislocations. By quantifying the temperature control rate and holding time, the dislocation density of germanium single crystal 60 after heat treatment is precisely set to 1×10⁻⁶. 2 ~5×10 3 cm -2 Within the range.

[0085] As a specific embodiment of the germanium single crystal dislocation level control method provided by the present invention, in step S1, multiple dislocation-free germanium single crystals 60 are marked with serial numbers; in step S2, they are placed into the mold 30 sequentially from bottom to top or from top to bottom according to the serial numbers. In the specific implementation of steps S1 and S2, by marking each dislocation-free germanium single crystal 60 with a unique serial number and placing them into the mold 30 sequentially (from bottom to top or from top to bottom), the serial number marking facilitates the precise positioning of each germanium single crystal 60 in the mold 30. Combined with the layered structure of the mold 30, the regularity of the heating positions of multiple germanium single crystals 60 in the furnace is ensured. In this way, a one-to-one correspondence between process parameters and germanium single crystals 60 can be achieved, facilitating the correlation analysis of subsequent dislocation test data, quickly locating the processing links of abnormal germanium single crystals 60, and improving process optimization efficiency.

[0086] Preferably, in the specific implementation of step S1, the head and tail of the dislocation-free germanium single crystal 60 are removed and tumbling are performed. During the growth of germanium single crystal 60, the head and tail are prone to potential defects due to stress concentration or impurity segregation. Removing the head and tail can ensure that the germanium single crystal 60 segment used for dislocation control is a pure dislocation-free core region. The germanium single crystal 60 is processed into a regular cylinder by tumbling process, so that the outer diameter is uniform and accurately matched with the support structure of mold 30.

[0087] As a specific implementation of the germanium single crystal dislocation level control method provided by the present invention, in the specific implementation of step S6, test pieces with a thickness of 5 mm are cut from the head and tail of the germanium single crystal 60 for dislocation testing. This is based on the characteristic that the two ends of the germanium single crystal 60 are easily affected by stress gradients during the growth process. The head and tail may have uneven dislocation distribution due to the difference in axial thermal field during heat treatment. Selecting the two ends for testing can comprehensively evaluate the overall dislocation uniformity of the germanium single crystal 60. The 5 mm thick test piece can ensure that there is enough volume to contain representative defects and facilitate subsequent chemical etching detection, avoiding the dislocation omission caused by being too thin or the increased detection difficulty caused by being too thick.

[0088] Preferably, argon is selected as the inert gas in step S4 because it is chemically inert and does not react chemically with germanium single crystal 60 at high temperatures. This effectively isolates oxygen and prevents oxidation damage to germanium single crystal 60. Argon has moderate thermal conductivity and stable density, which can uniformly fill the furnace space, promote a balanced thermal field distribution, and prevent abnormal dislocation proliferation caused by local temperature differences.

[0089] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for controlling the dislocation level in a germanium single crystal, characterized in that, include: S1: Prepare multiple dislocation-free germanium single crystals; S2: Multiple germanium single crystals are placed in layers inside the mold, with an installation gap between the germanium single crystals and the inner wall of the mold; S3: Place the mold inside the furnace, with the mold located at the center of the heater inside the furnace; S4: Evacuate the furnace body and fill it with inert gas to atmospheric pressure, setting the inert gas flow rate to 5-15 slm; S5: Start the heater and control the temperature inside the furnace as follows: 1) Increase the temperature inside the furnace from room temperature to 400-450℃ at a rate of 1-8℃ / min; 2) Increase the temperature inside the furnace to 650-700℃ at a rate of 0.5-3℃ / min; 3) Maintain the temperature inside the furnace at 650-700℃ and keep it at this temperature for 0.5-3 hours; 4) Reduce the temperature inside the furnace to 350-450℃ at a rate of 0.5-1.5℃ / h; 5) Reduce the temperature inside the furnace to 150-250℃ at a rate of 0.5-3℃ / h; 6) Reduce the temperature inside the furnace to room temperature at a rate of 1.5-4℃ / h; S6: Take out multiple germanium single crystals and perform dislocation tests on the germanium single crystal cut test pieces.

2. The method for controlling the dislocation level in a germanium single crystal as described in claim 1, characterized in that, In step S2, multiple annular support members arranged at intervals are installed on the mold, and the sum of the inner diameter and width of the annular support members is set to be greater than the outer diameter of the germanium single crystal; multiple germanium single crystals are placed on the multiple annular support members respectively.

3. The method for controlling the dislocation level in a germanium single crystal as described in claim 2, characterized in that, In step S3, the heaters are arranged in a ring on the inner wall of the furnace body, and a lifting rod is installed at the bottom of the furnace body, with a tray installed on the lifting rod; when the mold is placed in the furnace body, the mold is placed on the tray; then the lifting rod is activated to drive the mold to the center position of the heater.

4. The method for controlling the dislocation level in a germanium single crystal as described in claim 2, characterized in that, In step S2, the mold includes multiple sleeves stacked one on top of the other, and an annular support is installed inside each sleeve; the annular support includes multiple support blocks, which are fixedly installed on the inner wall of the sleeve and evenly spaced along the circumference of the sleeve; a groove for supporting germanium single crystal is opened on each support block, and the grooves on the multiple support blocks form a limiting groove for cooperating with the germanium single crystal.

5. The method for controlling the dislocation level in a germanium single crystal as described in claim 1, characterized in that, In step S5, the temperature change inside the furnace is set as follows: 1) The temperature inside the furnace is increased from room temperature to 420℃ at a rate of 6℃ / min; 2) Increase the temperature inside the furnace to 670℃ at a rate of 1℃ / min; 3) Maintain the furnace temperature at 670℃ and keep it at that temperature for 2 hours; 4) Reduce the temperature inside the furnace to 400℃ at a rate of 0.8℃ / h; 5) Reduce the temperature inside the furnace to 200℃ at a rate of 1℃ / h; 6) Reduce the temperature inside the furnace to room temperature at a rate of 2℃ / h.

6. The method for controlling the dislocation level in a germanium single crystal as described in claim 1, characterized in that, In step S1, serial numbers are marked on multiple dislocation-free germanium single crystals; in step S2, they are placed into the mold in order of serial numbers from bottom to top or from top to bottom.

7. The method for controlling the dislocation level in a germanium single crystal as described in claim 1, characterized in that, In step S1, the head and tail of the dislocation-free germanium single crystal are removed, and a cylindrical single crystal segment of the desired product size is obtained by rolling.

8. The method for controlling the dislocation level in a germanium single crystal as described in claim 1, characterized in that, In step S6, test pieces are cut from the head and tail of the extracted germanium single crystal for dislocation testing, and the thickness of the test pieces is 5 mm.

9. The method for controlling the dislocation level in a germanium single crystal as described in claim 1, characterized in that, In step S4, the inert gas is argon.

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