Gallium oxide crystal twin crystal inhibition growth method based on thermal field gradient induction

Abstract

The invention relates to the technical field of wide bandgap semiconductor material preparation, in particular to a gallium oxide crystal twin crystal inhibition growth method based on thermal field gradient induction, which comprises the following steps: preparing a gallium oxide crystal by adopting edge-defined film-fed growth equipment, and after the crystal enters a shouldering stage, regulating and controlling the power of a heater partition or starting a local cooling device to obtain the gallium oxide crystal twin crystal inhibition growth. Establishing a horizontal temperature gradient field in an area above the mold; according to the position and the extension direction of the twin crystal in the seed crystal, the low-temperature side of the horizontal temperature gradient field is arranged in the direction opposite to the extension direction of the twin crystal; maintaining the temperature gradient field in the horizontal direction for a period of time until the growth direction of the twin crystal deflects to the marginal area of the low-temperature side of the crystal; when the twin crystal is induced to the edge of the crystal or eliminated, the horizontal temperature gradient field is gradually reduced, the normal equal-diameter growth condition is recovered, the seed crystal does not need to be replaced, the twin crystal in the existing seed crystal can be directly inhibited, and the production cost and time are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of wide bandgap semiconductor material preparation, and in particular to a method for inhibiting the growth of gallium oxide crystal twins based on thermal field gradient induction. The method is particularly suitable for controlling and inhibiting twin defects during the growth of gallium oxide single crystals using the edge-defined film-fed growth (EFG) method. Background Art

[0002] As a new generation of ultra-wide bandgap semiconductor materials, β-Ga2O3 exhibits excellent properties, including a wide bandgap (approximately 4.8-4.9 eV), a high breakdown electric field (approximately 8 MV / cm), and excellent chemical stability. It exhibits broad application prospects in ultra-high voltage power devices, deep ultraviolet optoelectronics, high-brightness LEDs, and high-temperature, high-frequency electronic devices. As these applications continue to expand, the demand for high-quality, large-sized β-Ga2O3 single crystals is becoming increasingly urgent.

[0003] Currently, the main methods for preparing β-Ga2O3 single crystals include the Czochralski method, the guided-mode method (EFG), the vertical Bridgman method, and the floating zone method. Among them, the guided-mode method has become one of the main methods for producing large-size β-Ga2O3 single crystals due to its ability to control the shape and size of the crystal and its relatively high growth rate.

[0004] However, in the process of growing β-Ga2O3 crystals by the guided mode method, the twin defects present in the seed crystal often extend and expand during the subsequent growth process, and even run through the entire crystal, seriously affecting the quality and performance of the final crystal. In 2022, Professor Tao Xutang's team at Shandong University reported on the growth research of 4-inch β-Ga2O3 single crystals, mentioning that twin defects are still one of the main factors limiting the application of large-size β-Ga2O3 crystals. In addition, studies have shown that twins in β-Ga2O3 crystals can significantly reduce the breakdown voltage and carrier mobility of the device, thereby limiting its application in high-power electronic devices.

[0005] The current methods for suppressing twin defects in β-Ga2O3 crystals mainly include:

[0006] 1. Optimize seed crystal selection: Strictly screen seed crystals with no twins or very low twin content. However, this method is costly, inefficient, and cannot fundamentally solve the problem.

[0007] 2. Controlling the growth rate: reducing the formation and expansion of twins by reducing the growth rate, but this will significantly reduce production efficiency;

[0008] 3. Adjust the thermal field structure: Reduce thermal stress by optimizing the thermal field design, but the effect is limited and does not target the control of existing twins.

[0009] Some researchers have suggested that regulating the thermal field structure can improve crystal quality to a certain extent, but they have not yet proposed a systematic solution for effectively suppressing twinning. While optimizing growth parameters can reduce the probability of twin formation, there is still a lack of effective means to suppress existing twinning.

[0010] Therefore, it is urgent to develop a new method that can effectively inhibit the extension of twin defects without replacing the seed crystal, so as to improve the quality and production efficiency of β-Ga2O3 single crystals. Summary of the Invention

[0011] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for inhibiting the growth of gallium oxide crystal twins based on thermal field gradient induction. This method introduces a specific horizontal temperature gradient field during the crystal shouldering stage to change the melt supersaturation distribution and thermal stress state, thereby effectively controlling the growth direction of the twins, causing the twins to deflect toward the edge of the crystal, and ultimately inhibiting the extension of twin defects in the main crystal.

[0012] To achieve the above object, the present invention provides a method for inhibiting the growth of gallium oxide crystal twins based on thermal field gradient induction, comprising the following steps:

[0013] Gallium oxide crystals are prepared using a guided mold growth device. After the crystal enters the shouldering stage, a horizontal temperature gradient field is established in the area above the mold by regulating the power of the heater partition or activating a local cooling device.

[0014] According to the position and extension direction of the twin crystals in the seed crystal, the low temperature side of the horizontal temperature gradient field is set in the opposite direction of the extension direction of the twin crystals;

[0015] Maintaining the horizontal temperature gradient field for a period of time until the twin growth direction is observed to deflect to the edge region of the low-temperature side of the crystal;

[0016] When the twins are induced to the edge of the crystal or eliminated, the horizontal temperature gradient field is gradually reduced to restore normal equal-diameter growth conditions.

[0017] In a preferred embodiment of the present invention, the guided mold growth apparatus includes: a multi-zone independently controlled heating system, wherein independently controlled auxiliary heaters are installed on both sides of the area above the mold, the auxiliary heaters have a power range of 0-2000W, and a temperature control accuracy of ±1°C; an adjustable cooling device installed on one side of the area above the mold, the cooling device adopts water cooling or air cooling, the water cooling system has a flow control range of 0.5-5 liters per minute, and the air cooling system has a flow control range of 1-10 liters per minute; and a temperature monitoring system, including multiple thermocouples and infrared thermometers evenly distributed in the horizontal direction, for real-time monitoring of the temperature distribution near the growth interface.

[0018] Furthermore, the size of the horizontal temperature gradient field is 5-20°C per centimeter, and the specific gradient value is selected according to the type and severity of the twins: for mild twins with an area share of less than 5%, the horizontal temperature gradient is 5-8°C per centimeter; for medium twins with an area share of 5-15%, the horizontal temperature gradient is 8-15°C per centimeter; for severe twins with an area share of more than 15%, the horizontal temperature gradient is 15-20°C per centimeter.

[0019] Preferably, the time for maintaining the horizontal temperature gradient field is determined according to the severity of the twinning: for mild twinning with an area share of less than 5%, the maintenance time is 20-40 minutes; for moderate twinning with an area share of 5-15%, the maintenance time is 40-80 minutes; for severe twinning with an area share of more than 15%, the maintenance time is 80-120 minutes.

[0020] The present invention also provides a specific method for establishing a horizontal temperature gradient field, which can be achieved by any of the following methods: increasing the power of the auxiliary heater on the high-temperature side by 10-30% and reducing the power of the auxiliary heater on the low-temperature side by 5-15%; or keeping the power of the auxiliary heater on the high-temperature side unchanged, starting the cooling device on the low-temperature side, and starting the cooling intensity from the minimum value and gradually increasing it to the set value.

[0021] In addition, the rate of gradually reducing the horizontal temperature gradient field is 1-5°C per centimeter per hour, which is selected according to the twin deflection effect: for cases where the deflection effect is obvious, a faster rate of 3-5°C per centimeter per hour is adopted; for cases where the deflection effect is general, a medium rate of 2-3°C per centimeter per hour is adopted; for cases where the deflection effect is weak, a slower rate of 1-2°C per centimeter per hour is adopted.

[0022] The present invention is particularly suitable for suppressing β-Ga2O3 twin defects in different crystal orientations: when used to suppress <010> oriented twins, the horizontal temperature gradient is 10-15°C per centimeter, the gradient direction is perpendicular to the <010> direction, and the gradient is maintained for 40-60 minutes; when used to suppress <100> oriented twins, the horizontal temperature gradient is 8-12°C per centimeter, the gradient direction is perpendicular to the <100> direction, and the gradient is maintained for 50-70 minutes; when used to suppress <-201> oriented twins, the horizontal temperature gradient is 12-18°C per centimeter, the gradient direction is perpendicular to the <-201> direction, and the gradient is maintained for 30-50 minutes.

[0023] During the horizontal temperature gradient induction stage, in order to further improve the twinning suppression effect, the crystal growth rate is reduced to 65-85% of the original growth rate, and the crystal rotation speed is reduced to 4-9 revolutions per minute to reduce the influence of centrifugal force on melt flow; after the horizontal temperature gradient field is eliminated, the crystal growth rate is restored to 2-4 mm per hour, and the crystal rotation speed is restored to 10-20 revolutions per minute, and isodiametric growth is continued to the predetermined length.

[0024] The beneficial effects of the present invention include:

[0025] 1. By introducing a horizontal temperature gradient field, the growth direction of twins is effectively controlled, deflecting them to the edge of the crystal, thereby suppressing the extension of twins in the main crystal and significantly improving the crystal quality;

[0026] 2. This method does not require the replacement of seed crystals and can directly suppress twinning in existing seed crystals, reducing production costs and time;

[0027] 3. The horizontal temperature gradient parameters can be flexibly adjusted according to the specific type and position of the twins, and have strong applicability;

[0028] 4. The method is simple and easy to implement on existing guided mold growth equipment, with strong operability;

[0029] 5. By rationally controlling the thermal field gradient, not only can twinning be suppressed, but the density of other defects can also be reduced, thereby comprehensively improving the crystal quality. DETAILED DESCRIPTION

[0030] The present invention will be further described in detail below with reference to specific examples, but the embodiments of the present invention are not limited thereto.

[0031] In the implementation process of the present invention, it is first necessary to perform specific transformation and configuration on the conventional guided-mode crystal growth equipment to achieve precise control of the horizontal temperature gradient.

[0032] Generally speaking, guided mold growth equipment primarily consists of a growth chamber, a vacuum system, a gas system, a heating system, a crystal pulling system, and an observation system. The key to this invention lies in the specialized design of the heating system and the control method for the horizontal temperature gradient. The following describes the key equipment components in detail.

[0033] Conventional guided mold growth equipment typically employs an axisymmetric heating system to maintain a uniform temperature field. However, in this invention, we have specifically designed the heating system to precisely control the horizontal temperature gradient. Specifically, independently controlled auxiliary heaters are installed on either side of the area above the mold. These heaters can be individually adjusted in power, creating a controllable horizontal temperature gradient.

[0034] The auxiliary heater is made of tungsten wire (W, purity ≥99.95%) with a wire diameter of 0.5-0.8 mm. The coil design features an inner diameter of 40-60 mm, an outer diameter of 50-70 mm, a height of 20-40 mm, 15-25 turns, and a turn spacing of 1.5-2.5 mm. This design enables the auxiliary heater to provide a power density of 30-50 watts per square centimeter and a maximum operating temperature of 2200°C, which is sufficient to meet the temperature requirements for β-Ga2O3 crystal growth.

[0035] The auxiliary heater's power supply is controlled by a DC regulated power supply with a voltage range of 0-60 volts and a current range of 0-100 amps. The power control accuracy reaches ±0.5%, the response time does not exceed 100 milliseconds, and a PID control mode with adjustable parameters is used to ensure the accuracy and stability of temperature regulation.

[0036] In order to achieve more flexible horizontal temperature gradient control, the present invention also installs an adjustable cooling device on one side of the upper area of ​​the mold, which can be used in conjunction with the auxiliary heater or used alone to establish a horizontal temperature gradient.

[0037] There are two cooling system options: water cooling and air cooling. The water cooling system uses cooling tubes made of stainless steel (grade 316L) or copper (purity ≥99.9%) with an outer diameter of 6-10 mm and an inner diameter of 4-8 mm. The cooling medium is deionized water with a resistivity greater than 10 megohm·cm. The system is equipped with a constant temperature water circulation device with a temperature control range of 15-40°C and an accuracy of ±0.5°C. The flow rate is controlled by an electromagnetic flowmeter with a range of 0.5-5 liters per minute and an accuracy of ±2%. The pressure is controlled at 0.2-0.5 MPa and is equipped with a pressure sensor and a safety relief valve.

[0038] The air-cooling system uses high-purity argon (≥99.999%) as the cooling medium, delivered through stainless steel or copper tubing with an outer diameter of 8-12 mm and an inner diameter of 6-10 mm. The flow rate is precisely regulated by a mass flow controller within a range of 1-10 liters per minute with an accuracy of ±1%. To improve cooling efficiency, the system can be equipped with an optional gas cooling unit with a temperature control range of 10-30°C.

[0039] Both cooling systems are equipped with a three-axis fine-tuning mechanism with an adjustment accuracy of ±0.5 mm, an adjustment range of ±15 mm on the X and Y axes, and ±30 mm on the Z axis, to precisely control the cooling position.

[0040] Accurate temperature monitoring is the key to achieving precise control of horizontal temperature gradient. The present invention adopts a multi-point temperature monitoring system, including a thermocouple array and an infrared temperature measurement system.

[0041] Five W-5% Re / W-26% Re thermocouples with diameters of 0.3-0.5 mm are evenly spaced horizontally above the mold. They have a temperature measurement range of 0-2300°C, an accuracy of ±2°C or 0.5% of reading (whichever is greater), and a response time of no more than 1 second. The thermocouples are spaced 10-15 mm apart and 10-30 mm from the growth interface to comprehensively monitor the horizontal temperature distribution.

[0042] The system is also equipped with a two-color infrared thermometer with a wavelength range of 0.7-1.1 microns, a temperature measurement range of 600-2000°C, an accuracy of ±3°C or 0.3% of reading (whichever is greater), a field of view of 1-3°, and a response time of no more than 10 milliseconds. The infrared thermometer is aimed at the growth interface through an observation window, enabling non-contact temperature monitoring.

[0043] The temperature data acquisition system features an adjustable sampling frequency of 1-10 Hz, no fewer than 16 channels, a resolution of at least 16 bits, RS-485, USB, and Ethernet interfaces, a data storage capacity of at least 1TB, and remote data transmission. The system software includes real-time display, historical curve query, alarm settings, and data export capabilities, providing reliable assurance for precise control of horizontal temperature gradients.

[0044] Before specifically describing the core technology of the present invention, the thermal field gradient-induced twinning suppression method, the basic process of β-Ga2O3 crystal growth is briefly introduced, including raw material preparation, seed crystal processing, crystal growth and post-processing.

[0045] 1. Raw Material Preparation: The primary raw material used in this invention is high-purity β-Ga2O3 powder (gallium dioxide) with a purity of no less than 99.999% (5N) and an average particle size between 1 and 5 microns. This powder can be purchased from Sigma-Aldrich or AlfaAesar. The main impurity levels in the raw material must be less than 2 ppm for Si, less than 1 ppm for Al, less than 1 ppm for Fe, and less than 1 ppm for Ca. The total amount of other metallic impurities should be less than 5 ppm.

[0046] In order to further improve the purity of the raw materials, the commercial raw materials need to be pretreated. Specifically, the β-Ga2O3 powder is calcined at 800±20℃ for 4-6 hours to remove moisture and organic matter adsorbed on the surface; then it is cooled to room temperature in a high-purity argon (purity ≥99.999%) atmosphere and stored in a drying oven with a relative humidity of less than 10%. The treated raw materials need to be tested for metal impurity content using inductively coupled plasma mass spectrometry (ICP-MS) to ensure that the above requirements are met.

[0047] 2. Seed Crystal Preparation: Seed crystal selection is a key factor influencing the final crystal quality. The present invention uses <010> or <100> oriented β-Ga2O3 single crystals as seed crystals, with dimensions of (5±0.5) mm × (5±0.5) mm × (20±2) mm.

[0048] The seed crystal processing process includes cutting, polishing, and surface cleaning. First, the crystal is cut to the desired size using a diamond wire saw at a cutting speed of 0.5-1 mm / min, using deionized water with a resistivity greater than 18.2 megohm-cm. The seed crystal is then mechanically polished using diamond polishing pastes with particle sizes of 9 microns, 6 microns, 3 microns, and 1 micron, for 20 minutes, 15 minutes, 10 minutes, and 5 minutes, respectively. The polished seed crystal is ultrasonically cleaned with anhydrous ethanol (purity ≥99.5%) for 15 minutes, then rinsed with deionized water for 10 minutes, and finally dried at 100°C for 2 hours.

[0049] Seed crystal quality testing uses X-ray diffractometer (XRD) to examine crystal orientation, requiring a deviation of less than 2°. A polarizing microscope is used to examine twin distribution and mark the twin positions and extension directions. X-ray rocking curve (XRC) analysis is used to measure seed crystal quality, with the (400) plane full width at half maximum (FWHM) required to be less than 100 arc seconds. These test results will provide important guidance for subsequent horizontal temperature gradient design.

[0050] 3. Preparation for crystal growth: Before crystal growth, the growth system needs to be pre-treated. First, the growth chamber is vacuumed to 1×10 -4The system is then purge-treated to a pressure below 100 Pa, with a vacuum time of at least 2 hours. High-purity argon is then filled to 101.3 kPa, and this is repeated three times to complete the gas replacement. During the system purge phase, a mixture of oxygen (purity ≥ 99.995%) and argon (oxygen volume fraction 10-20%) is introduced at a flow rate of 50-100 standard cubic centimeters per minute (sccm) for 8-12 hours.

[0051] During the raw material melting stage, load 200-300 grams of β-Ga2O3 powder into the crucible, depending on the crucible's capacity. The temperature is raised from room temperature to 1500°C at a rate of 3-5°C per minute, held for 1 hour; then raised to 1820±10°C (the melting point of β-Ga2O3 is approximately 1820°C) at a rate of 2-3°C per minute, held for 2-4 hours to ensure complete melting. To ensure a uniform melt composition, rotate the crucible at 10-15 rpm for 4-6 hours while the melt is in the process.

[0052] During the seed crystal preheating and melt contact stage, the seed crystal is first slowly lowered to approximately 10 mm from the melt surface and held for 30-60 minutes to preheat the seed crystal to 1500-1600°C. The seed crystal is then lowered at a rate of 0.5-1 mm / min until it contacts the melt surface, observing that the melt wets the bottom of the seed crystal. The seed crystal is immersed in the melt to a depth of 1-2 mm and held for 10-15 minutes to allow the system to reach thermal equilibrium.

[0053] 4. Neck Growth and Isodiametric Growth: Neck growth is a critical step in crystal growth. The initial pulling speed is set at 0.5-1 mm / min. Once the liquid surface separates from the seed crystal and a liquid neck is formed, the pulling speed is reduced to 0.3-0.5 mm / h. The neck diameter is controlled at 3-5 mm and the length is 10-15 mm. During this stage, the seed crystal is rotated at a speed of 5-10 rpm in a clockwise direction, while maintaining an oxygen partial pressure of 0.1-0.2 atmospheres (10-20 kPa).

[0054] After neck growth is complete, the isodiameter growth phase begins. During this phase, the growth rate is maintained at 1-3 mm / hour, the rotation speed is 10-15 rpm, and the melt temperature is maintained at 1825-1835°C by adjusting the power of the main heater. A CCD camera is used to monitor the crystal diameter in real time, and the pulling speed and temperature are adjusted to maintain a stable diameter of 15±1 mm. After the isodiameter phase reaches a length of 30-50 mm, the shoulder release phase is ready.

[0055] The core innovation of this invention lies in introducing a horizontal temperature gradient during the crystal shouldering stage, which modulates the growth environment of twins and deflects them to the crystal edge, effectively suppressing twin defects. This process is described in detail below.

[0056] 1. Shoulder Release Phase Parameter Settings: When the length of the uniformly grown crystal reaches 30-50 mm, the shoulder release phase begins. The goal of this phase is to gradually expand the crystal diameter from 15 mm to 25-30 mm, with the expansion rate controlled at 0.3-0.5 mm / hour. To ensure stability during the shoulder release process, the pulling speed is reduced to 0.8-1.2 mm / hour and the rotation speed is reduced to 5-8 rpm to minimize the impact of centrifugal force on melt flow.

[0057] 2. Establishing a horizontal temperature gradient: When the crystal diameter expands to 18-20 mm, the horizontal temperature gradient control system is activated based on the previous observations of the position and extension direction of the twins in the seed crystal. Determining the gradient direction is crucial. The low-temperature side needs to be set opposite the twin extension direction to encourage the twins to deflect toward the low-temperature side.

[0058] There are two main methods for establishing a horizontal temperature gradient:

[0059] The first method is to adjust the auxiliary heater power. Specifically, increase the power of the high-temperature side auxiliary heater by 10-30% at a rate of 3-5% per minute; simultaneously reduce the power of the low-temperature side auxiliary heater by 5-15% at a rate of 2-3% per minute. This way, the desired horizontal temperature gradient can be established within 15-30 minutes.

[0060] The second method is to activate the cooling device. In this method, the power of the high-side auxiliary heater remains unchanged, while the low-side cooling device is activated. The cooling intensity starts at the minimum setting and is increased at a rate of 5-10% per minute to the set value. This method typically takes 20-35 minutes to establish the desired temperature gradient.

[0061] During the entire process, the temperature distribution in the area above the mold is monitored in real time through a thermocouple array and an infrared temperature measurement system to ensure that the horizontal temperature gradient is stable within the set range.

[0062] 3. Optimizing horizontal temperature gradient parameters: The magnitude of the horizontal temperature gradient needs to be optimized based on the type and severity of twinning. For mild twinning (less than 5% of the area), a horizontal temperature gradient of 5-8°C per centimeter is recommended; for moderate twinning (5-15% of the area), a horizontal temperature gradient of 8-15°C per centimeter is recommended; for severe twinning (greater than 15% of the area), a horizontal temperature gradient of 15-20°C per centimeter is recommended.

[0063] The gradient maintenance time also needs to be determined according to the severity of twinning: for mild twinning, the maintenance time is 20-40 minutes; for moderate twinning, the maintenance time is 40-80 minutes; for severe twinning, the maintenance time is 80-120 minutes.

[0064] It is important to note that the horizontal temperature gradient should not be too large, with a maximum of no more than 25°C per centimeter, otherwise new defects may be introduced. At the same time, the gradient should not be too small, with a minimum of no less than 5°C per centimeter, otherwise the twin deflection effect will be insignificant. The maximum maintenance time of the gradient should not exceed 120 minutes, as prolonged maintenance of this time may lead to a decrease in the overall quality of the crystal.

[0065] 4. Twin deflection process monitoring: Under the influence of a horizontal temperature gradient, twin deflection is observed in real time using a CCD camera in conjunction with a polarized light system. Significant deflection is indicated when the twin growth direction deviates from the main crystal growth axis by more than 30° and moves toward the low-temperature edge. At this point, the twin position and deflection angle can be recorded every 10 minutes to create a deflection curve for more precise control of the gradient maintenance time.

[0066] 5. Restoring normal growth conditions: Once the twins have been successfully induced to the crystal edge or completely eliminated, the horizontal temperature gradient needs to be gradually reduced to restore normal growth conditions. The choice of reduction rate depends on the deflection effect of the twins: for obvious deflection effects, a faster rate of 3-5°C per centimeter per hour can be used; for moderate deflection effects, a medium rate of 2-3°C per centimeter per hour can be used; for weak deflection effects, a slower rate of 1-2°C per centimeter per hour can be used.

[0067] If the horizontal temperature gradient is established by the heater power control method, the power of the high-temperature side and low-temperature side heaters is gradually restored to a balanced state; if the cooling device control method is adopted, the cooling intensity of the cooling device is gradually reduced to zero.

[0068] To restore the normal axial temperature distribution, adjust the axial temperature gradient to 30-50°C per centimeter (near the solid-liquid interface) for 30-60 minutes to ensure the temperature field is stable. Monitor the axial temperature distribution through a vertical thermocouple array to ensure normal recovery.

[0069] When normal isodiametric growth parameters are restored, the growth rate is restored to 2-4 mm / h, the rotation speed is restored to 10-20 rpm, the oxygen partial pressure is maintained at 0.1-0.2 atmospheres (10-20 kPa), and the melt temperature is controlled at 1825-1835°C. During this stage, close attention should be paid to diameter fluctuation control (≤±0.5 mm), surface quality, and interface shape to ensure stable crystal quality.

[0070] After the crystal growth is completed, reasonable cooling and post-processing are required to eliminate the thermal stress generated during the growth process and further improve the crystal quality.

[0071] 1. Crystal separation: Once the crystal has grown to a predetermined length (typically 80-120 mm), the separation process begins. Initially, the pulling speed is increased to 5-8 mm / h while simultaneously lowering the melt temperature by 2-5°C. When a narrow neck is observed forming between the bottom of the crystal and the melt, the pulling speed is further increased to 10-15 mm / h to achieve rapid separation. Once separation is complete, the crystal is immediately lifted to the upper area of ​​the heat field (approximately 1200-1400°C) to prepare for the cooling process.

[0072] 2. Cooling Procedure: The crystal is cooled in two stages: the first stage (1800-800°C) is a cooling rate of 2-5°C per minute, lasting approximately 4-8 hours; the second stage (800°C to room temperature) is a cooling rate of 1-2°C per minute, lasting approximately 10-14 hours. Specifically, within the 1800-1500°C range, the cooling rate is 2-3°C per minute; within the 1500-1200°C range, the cooling rate is 3-4°C per minute; within the 1200-800°C range, the cooling rate is 4-5°C per minute; within the 800-500°C range, the cooling rate is 1.5-2°C per minute; within the 500-300°C range, the cooling rate is 1-1.5°C per minute; and from 300°C to room temperature, the cooling rate is 0.5-1°C per minute. During the cooling process, the oxygen partial pressure is maintained at 0.1-0.2 atmospheres (10-20 kPa).

[0073] 3. Annealing: To eliminate thermal stress generated during growth, the crystal requires annealing. The annealing temperature is selected within the range of 950-1100°C, preferably 1000-1050°C; the annealing time is 6-24 hours, preferably 10-16 hours; the annealing atmosphere is air or a mixed gas containing 20-30% oxygen, and the pressure is 101.3±5 kPa. The heating rate is controlled at 1-3°C per minute, and the cooling rate is 0.5-2°C per minute. The annealing apparatus uses a box-type electric furnace with MoSi2 or SiC heating elements, with a temperature uniformity of no more than ±5°C.

[0074] 4. Surface treatment: Crystal surface treatment includes three steps: mechanical grinding, mechanical polishing and chemical mechanical polishing (CMP). In the mechanical grinding stage, silicon carbide (SiC) sandpaper with particle sizes of 60 mesh, 120 mesh, 240 mesh, 400 mesh, 600 mesh and 1000 mesh is used for grinding in sequence, and the grinding time for each particle size is 10-20 minutes. In the mechanical polishing stage, diamond polishing pastes of 9 microns, 6 microns, 3 microns, 1 micron and 0.5 microns are used for polishing in sequence, and the polishing time for each particle size is 15-30 minutes. In the chemical mechanical polishing stage, an alkaline polishing liquid with a pH value of 10-12 is used (the main component is colloidal silica, with a concentration of 5-10 weight percent), the polishing time is 30-60 minutes, the polishing pressure is 20-40 kPa, and the rotation speed is 40-60 revolutions per minute. The final surface cleaning step is to use deionized water, acetone (purity ≥99.5%), and isopropyl alcohol (purity ≥99.5%) for ultrasonic cleaning in sequence, with each solvent cleaning for 10-15 minutes.

[0075] The thermal field gradient induced twinning suppression method proposed in the present invention has the following three main mechanisms:

[0076] 1. Supersaturation Distribution Control Mechanism: During the guided-mode growth of β-Ga2O3 crystals, Ga2O3 molecules in the melt undergo diffusion, adhesion, and crystal growth. The driving force behind this process is the supersaturation of the melt, defined as σ = (C-Ceq) / Ceq = (Tm-T) / Tm, where C is the actual concentration in the melt, Ceq is the equilibrium concentration, Tm is the equilibrium melting point, and T is the actual temperature.

[0077] When a horizontal temperature gradient is introduced, the supersaturation on the low temperature side is higher than that on the high temperature side, resulting in a growth rate V1 = k·σ1 on the low temperature side. n Greater than the growth rate on the high temperature side V2 = k·σ2 n , where k is the kinetic coefficient (about 0.5-2.0×10 -5 m / s), n is an exponent (about 1.5-2.5).

[0078] When twins grow in regions with different growth rates, they naturally deflect toward the region with higher growth rate. Therefore, the horizontal temperature gradient, by regulating the local supersaturation distribution, causes the twins to naturally deflect their growth toward the lower temperature side.

[0079] Experiments have shown that a horizontal temperature gradient of 10°C per centimeter can result in a 15-25% difference in growth rate, sufficient to cause significant twinning. The critical deflection angle θc = arctan[(Vlow - Vhigh) / Vaverage], where Vlow is the growth rate on the low-temperature side, Vhigh is the growth rate on the high-temperature side, and Vaverage is the average growth rate.

[0080] 2. Thermal stress induction mechanism: β-Ga2O3 has a significant anisotropic thermal expansion coefficient: α

[100] =(3.5-4.5)×10 -6 K-1, α

[010] = (2.8-3.8) × 10 -6 K-1, α

[001] =(4.2-5.2)×10 -6 K-1. When a horizontal temperature gradient is applied, an inhomogeneous thermal stress field is generated inside the crystal. This thermal stress field interacts with the twin interface, generating a driving force F = σth·b·cosθ, where σth is the thermal stress, b is the Burgers vector, and θ is the angle between the stress direction and the normal to the twin plane.

[0081] Thermal stress can be calculated using the formula σth = E·α·ΔT / (1-ν), where E is Young's modulus (approximately 200-250 GPa), α is the coefficient of thermal expansion, and ν is Poisson's ratio (approximately 0.25-0.30). When the horizontal temperature gradient is 10°C per centimeter, the thermal stress generated is approximately 2-5 MPa, which exceeds the critical stress for twin interface migration (approximately 1.5-3.0 MPa) and is sufficient to drive the twins to move toward the low-stress region (usually the low-temperature side).

[0082] When the thermal stress exceeds a critical value, it can promote the migration of the twin interface. This theory provides important theoretical support for the present invention.

[0083] 3. Interface morphology control mechanism: A horizontal temperature gradient changes the shape of the solid-liquid interface from a flat surface to a curved state. The relationship between the interface curvature radius R and the temperature gradient G is: R ≈ λ / G, where λ is the thermal conductivity at the solid-liquid interface front (approximately 10-15 W / m·Kelvin).

[0084] When the horizontal temperature gradient is 10°C per centimeter, the interface curvature changes by about 2-4 mm. The relationship between the interface tilt angle θ and the horizontal temperature gradient ΔT is: θ ≈ arctan(ΔTh / ΔTv), where ΔTh is the horizontal temperature gradient and ΔTv is the vertical temperature gradient.

[0085] Changes in interface morphology have a significant impact on the growth direction of twins: the curved interface increases the angle between the twin growth direction and the main crystal growth direction; when the curvature reaches a critical value, the twins will grow along the tangent direction of the interface; ultimately, the twins gradually deviate from the main crystal, or even completely move out of the effective growth area.

[0086] When the interface curvature radius is less than 10-15 mm, the twin deflection effect is most significant, and this conclusion is highly consistent with the experimental observation results of the present invention.

[0087] The technical solutions and effects of the present invention are described in detail below through specific embodiments.

[0088] Example 1: Suppression of <010> twinning induced by a mild horizontal temperature gradient

[0089] Raw materials and seed crystal preparation:

[0090] β-Ga2O3 powder (Sigma-Aldrich) with a purity of 99.999% was used as the raw material. After calcination at 800°C for 5 hours, it was placed in a high-purity iridium crucible with a charge of 250 grams. A single crystal of β-Ga2O3 with a <010> orientation, measuring 5 mm × 5 mm × 20 mm, was selected as the seed crystal. Polarizing microscopy confirmed the presence of a small amount of twins in the seed crystal, accounting for approximately 5% of the area.

[0091] Growth process:

[0092] The crucible containing the raw materials was heated to 1825°C to completely melt the Ga2O3, and the mixture was held for 4 hours to homogenize. The seed crystal was preheated to approximately 1550°C and placed in contact with the melt, with a wetting depth of 1.5 mm. This was held for 15 minutes to allow the system to reach thermal equilibrium. The seed crystal was then pulled at a rate of 0.8 mm / min to form a neck with a controlled diameter of 4 mm and a length of 12 mm. This was followed by isotropic growth at a rate of 1.5 mm / h until the diameter reached 15 mm and the length reached 40 mm.

[0093] Horizontal temperature gradient induction process:

[0094] When the crystal entered the shouldering stage (diameter expanded from 15 mm to 25 mm), the horizontal temperature gradient control system was activated when the crystal diameter reached 18 mm. Based on the position and extension direction of the twins in the seed crystal, the low-temperature side was set opposite the twin extension direction. By increasing the power of the auxiliary heater on the high-temperature side by 15% and activating the low-temperature side cooling device at the same time, a horizontal temperature gradient of 6°C per centimeter was formed in the area above the mold. The pulling speed was reduced to 1.2 mm / h and the rotation speed was reduced to 7 rpm. This horizontal temperature gradient was maintained for 30 minutes, and the twin growth was monitored in real time using a polarized light observation system. The twins began to deflect toward the low-temperature side. When the deflection angle reached approximately 25°, the horizontal temperature gradient was gradually reduced at a rate of 4°C per centimeter per hour. It took about 1.5 hours to restore the normal temperature distribution. Normal isodiametric growth conditions were then restored, with a pulling speed of 3 mm / h and a rotation speed of 15 rpm, and growth continued to a total length of 100 mm.

[0095] Cooling and post-processing:

[0096] After crystal growth is complete, the temperature is lowered to 800°C at a rate of 3°C per minute, and then cooled to room temperature at a rate of 1.5°C per minute. The crystal is then placed in an annealing furnace and held at 1000°C for 12 hours to eliminate thermal stress. After conventional surface treatment, the crystal quality is assessed using methods such as polarizing microscopy, X-ray diffraction, and the etch pit method.

[0097] Result analysis:

[0098] After thermal field gradient induction treatment, the deflection angle of the <010> twin is about 25°, the twin area reduction rate reaches about 65%, and the overall quality of the crystal is good, with no obvious new defects. The dislocation density is 2.3×10 4 cm-2, the carrier concentration is 6.5×10 16 The results show that even a slight horizontal temperature gradient can have a significant effect on the growth direction of twins.

[0099] Example 2: Moderate Horizontal Temperature Gradient Induced <100> Twinning Suppression

[0100] Raw materials and seed crystal preparation:

[0101] β-Ga2O3 powder (Alfa Aesar) with a purity of 99.999% was used as the raw material, with a charge of 270 g. A <100>-oriented β-Ga2O3 single crystal measuring 5.5 mm × 5.5 mm × 22 mm was used as the seed crystal. Polarizing microscopy revealed a moderate presence of twins within the seed crystal, accounting for approximately 10% of the area.

[0102] Growth process:

[0103] The raw material melt temperature was controlled at 1830°C and maintained for 5 hours to achieve full melt homogenization. The seed crystal was preheated to 1580°C and then placed in contact with the melt, with a wetting depth of 1.8 mm. A neck was formed at a rate of 0.7 mm / min, resulting in a diameter of 3.5 mm and a length of 15 mm. This was followed by isotropic growth at a rate of 1.8 mm / h to a diameter of 15 mm and a length of 45 mm.

[0104] Horizontal temperature gradient induction process:

[0105] When the crystal diameter expanded to 20 mm, the horizontal temperature gradient control system was activated. The low-temperature side was set opposite the direction of extension of the <100> twins. Using method 1, the power of the auxiliary heater on the high-temperature side was increased by 22% while the power on the low-temperature side was reduced by 10%, creating a horizontal temperature gradient of 10°C per centimeter in the area above the mold. The pulling speed was reduced to 1.5 mm / h, and the rotation speed was reduced to 6 rpm. This horizontal temperature gradient was maintained for 60 minutes, and the twins clearly deflected toward the low-temperature side, reaching a deflection angle of approximately 38°. The horizontal temperature gradient was then gradually reduced at a rate of 3°C per centimeter per hour, restoring the normal temperature distribution in approximately 3.3 hours. Normal isodiametric growth conditions were restored, with a pulling speed of 3.5 mm / h and a rotation speed of 18 rpm, and growth continued to a total length of 110 mm.

[0106] Cooling and post-processing:

[0107] A staged cooling strategy was employed: 2.5°C / min from 1800-1500°C, 3.5°C / min from 1500-1200°C, 4.5°C / min from 1200-800°C, 1.8°C / min from 800-500°C, 1.2°C / min from 500-300°C, and 0.8°C / min from 300°C to room temperature. Annealing was performed at 1050°C for 14 hours in an atmosphere containing 25% oxygen.

[0108] Result analysis:

[0109] The deflection angle of the <100> twin reaches about 38°, and the twin area reduction rate is about 85%. The overall quality of the crystal is good, and only a slight increase in thermal stress is observed in local areas. The dislocation density is 1.8×10 4 cm-2, the carrier concentration is 7.2×10 16 cm-3, and the Hall mobility is 95 cm2 / V·s (at room temperature). Moderate horizontal temperature gradients show stronger twinning suppression effects and have less impact on the overall quality of the crystal.

[0110] Example 3: Intensity-level temperature gradient-induced twinning suppression of <-201>

[0111] Raw materials and seed crystal preparation:

[0112] β-Ga2O3 powder with a purity of 99.999% was used as the raw material, with a charge of 300 grams. A single crystal of β-Ga2O3 with a <-201> orientation, measuring 4.5 mm × 4.5 mm × 18 mm, was selected as the seed crystal. Polarizing microscopy revealed the presence of numerous twins within the seed crystal, accounting for approximately 18% of the area.

[0113] Growth process:

[0114] The raw material melt temperature was controlled at 1835°C for 6 hours. The seed crystal was preheated to 1600°C and then exposed to the melt, with a wetting depth of 2 mm. A neck was formed at a rate of 0.6 mm / min, with a diameter of 4 mm and a length of 14 mm. This was followed by isotropic growth at a rate of 2 mm / h to a diameter of 15 mm and a length of 35 mm.

[0115] Horizontal temperature gradient induction process:

[0116] When the crystal diameter expanded to 19 mm, the horizontal temperature gradient control system was activated. The low-temperature side was set opposite the direction of the <-201> twin extension. Method 2 was used, maintaining the power of the auxiliary heater on the high-temperature side constant and activating the low-temperature air cooling system. The cooling gas flow rate began at 2 liters per minute and was gradually increased to 8 liters per minute, creating a horizontal temperature gradient of 18°C ​​per centimeter in the area above the mold. The pulling speed was reduced to 1.3 mm / hour, and the rotation speed was reduced to 5 rpm. This horizontal temperature gradient was maintained for 45 minutes, during which the twins rapidly deflected toward the low-temperature side, reaching a deflection angle of approximately 45°. The horizontal temperature gradient was then gradually reduced at a rate of 2°C per centimeter per hour, restoring the normal temperature distribution in approximately 9 hours. Normal isodiametric growth conditions were restored, with a pulling speed of 4 mm / hour and a rotation speed of 20 rpm, and growth continued until a total length of 120 mm.

[0117] Cooling and post-processing:

[0118] A fine-segmented cooling strategy was employed, with a total cooling time of approximately 20 hours. Annealing was performed at 1080°C for 16 hours in air. Surface treatment involved mechanical grinding, mechanical polishing, and chemical mechanical polishing, with a polishing solution pH of 11.5.

[0119] Result analysis:

[0120] The deflection angle of the twins in the <-201> crystal reached about 45°, and the twin area reduction rate was as high as 95%, which was a significant effect. However, a small number of new dislocations appeared on the high-temperature side of the crystal, and the dislocation density increased to 2.8×10 4 cm-2, the carrier concentration is 8.1×10 16 cm-3, the Hall mobility is 88 cm 2 / V·second (room temperature). This shows that although the strong horizontal temperature gradient has the best effect on twinning suppression, it may introduce new defects and needs to be used with caution.

[0121] Example 4: Optimization of simultaneous suppression of multiple types of twins

[0122] Raw materials and seed crystal preparation:

[0123] The raw material used was 280 grams of β-Ga2O3 powder with a purity of 99.999%. A single β-Ga2O3 crystal containing both <010> and <100> twins was selected as the seed crystal, measuring 5 mm × 5 mm × 20 mm. The combined area of ​​the two twins accounted for approximately 12%.

[0124] Growth process:

[0125] The standard procedures of raw material melting, seed preheating, neck growth and initial isodiameter growth were carried out.

[0126] Horizontal temperature gradient induction process:

[0127] To address the coexistence of two types of twins, a two-stage gradient induction strategy was employed. In the first stage, a horizontal temperature gradient of 12°C / cm2 was applied perpendicular to the extension direction of the <010> twins for 50 minutes, causing the <010> twins to begin to deflect. In the second stage, the horizontal temperature gradient was adjusted perpendicular to the extension direction of the <100> twins for 55 minutes, causing the <100> twins to begin to deflect. The pulling speed was maintained at 1.4 mm / h, and the rotation speed was 6 rpm. After completing the two-stage treatment, the horizontal temperature gradient was gradually reduced at a rate of 2.5°C / cm2 per hour to restore normal growth conditions.

[0128] Result analysis:

[0129] The two-stage gradient induction strategy significantly inhibited both types of twins. The deflection angle of the <010> twin was approximately 32°, with an area reduction rate of approximately 75%. The deflection angle of the <100> twin was approximately 35°, with an area reduction rate of approximately 80%. The overall quality of the crystal was good, with a dislocation density of 2.1×10 4 cm-2, the carrier concentration is 7.5×10 16 cm-3, the Hall mobility is 98 cm 2 This indicates that the phased gradient induction strategy can achieve good results when multiple types of twins coexist.

[0130] Example 5: Parameter Optimization Example - Effect of Gradient Duration

[0131] In order to study the effect of horizontal temperature gradient duration on twinning suppression, three groups of different gradient durations were set while keeping other parameters the same:

[0132] Experimental conditions:

[0133] The raw materials and seed crystals were prepared in the same manner as in Example 2. The horizontal temperature gradient was fixed at 10°C per centimeter, and the gradient direction was perpendicular to the extension direction of the <100> twins.

[0134] Three sets of experiments:

[0135] Experimental group A: gradient duration was 30 min;

[0136] Experimental group B: gradient duration was 60 min;

[0137] Experimental group C: gradient duration was 90 minutes.

[0138] Result analysis:

[0139] Experimental group A (30 minutes): the twinning deflection angle is about 20°, and the area reduction rate is about 45%;

[0140] Experimental group B (60 minutes): the twinning deflection angle is about 38°, and the area reduction rate is about 85%;

[0141] Experimental group C (90 minutes): The twin deflection angle was about 42° and the area reduction rate was about 90%, but a slight increase in thermal stress was observed in the crystal.

[0142] The results show that the gradient duration significantly affects twinning suppression, but this needs to be balanced against potential negative effects. For <100> twins, a gradient duration of 60 minutes achieves good results, while further extensions yield diminishing returns and may introduce new defects.

[0143] In order to verify the effectiveness and superiority of the present invention, the following comparative examples were designed:

[0144] Comparative Example 1: Conventional guided mode growth without horizontal temperature gradient

[0145] Experimental conditions:

[0146] The raw materials and seed crystal preparation were the same as those in Example 2, but no horizontal temperature gradient was introduced during the entire growth process, and only a conventional axisymmetric thermal field was used.

[0147] Growth process:

[0148] The raw material melting, seed crystal preheating, neck growth, equal diameter growth and shoulder release processes were carried out according to the standard procedure, with a pulling speed of 1.8 mm per hour and a rotation speed of 12 revolutions per minute.

[0149] Result analysis:

[0150] Under the condition of no horizontal temperature gradient, the <100> twins extended from the seed crystal to the entire crystal, and no obvious deflection was observed. The twin area in the final crystal accounted for about 12%, slightly higher than the initial value in the seed crystal, and the dislocation density was 3.2×10 4 cm-2, the carrier concentration is 6.8×101 6cm-3, the Hall mobility is 85 cm 2 / V·s (room temperature). The results show that the conventional guided mode method cannot effectively suppress the twin extension.

[0151] Comparative Example 2: Guided Mode Growth with Excessive Horizontal Temperature Gradient

[0152] Experimental conditions:

[0153] The raw materials and seed crystal preparation were the same as in Example 3, but the horizontal temperature gradient was set to 25°C per centimeter, which is much higher than the recommended value.

[0154] Growth process:

[0155] During the shoulder release stage, a strong horizontal temperature gradient of 25 °C per centimeter was introduced, with the gradient direction perpendicular to the extension direction of the <-201> twins, and the maintenance time was 40 minutes.

[0156] Result analysis:

[0157] Although the deflection angle of the <-201> twins reached about 50° and the area reduction rate was as high as 98%, a large number of new defects appeared in the crystal. In particular, a clear dislocation network was observed on the high-temperature side, and the dislocation density increased to 5.7×10 4 cm-2. Furthermore, significant deformation and cracks appeared on the crystal surface, seriously affecting the overall quality of the crystal. The results show that while excessively large horizontal temperature gradients can improve twinning suppression, they can introduce more defects, which is not worth the cost.

[0158] Comparative Example 3: Guided Mode Growth with Only Reduced Growth Rate

[0159] Experimental conditions:

[0160] The raw materials and seed crystal preparation were the same as those in Example 1, and no horizontal temperature gradient was introduced. However, the growth rate was reduced to 0.8 mm / h during the shoulder release stage, which was much lower than the conventional value.

[0161] Growth process:

[0162] A low growth rate of 0.8 mm per hour was maintained throughout the shouldering phase and the subsequent isodiametric growth phase, and the rotation speed was maintained at 15 revolutions per minute.

[0163] Result analysis:

[0164] Under low growth rate conditions, the extension rate of the 〈010〉 twins decreased, but no obvious deflection was observed. The twin area in the final crystal accounted for about 4.8%, slightly lower than the initial value, and the dislocation density was 2.5×10 4 cm-2, the carrier concentration is 6.7×10 16 cm-3, the Hall mobility is 95 cm 2Although the low growth rate has a certain effect on suppressing the formation of new twins, it has a limited effect on suppressing existing twins and significantly reduces production efficiency.

[0165] Comparative Example 4: Guided Mode Growth with Simple Rotational Direction Change

[0166] Experimental conditions:

[0167] The raw materials and seed crystals were prepared in the same manner as in Example 2, without introducing a horizontal temperature gradient. However, the rotation direction was changed from clockwise to counterclockwise during the shouldering stage, and the rotation speed remained unchanged at 12 revolutions per minute.

[0168] Growth process:

[0169] At the beginning of the shoulder release phase, the rotation direction was changed to counterclockwise rotation for 60 minutes and then returned to clockwise rotation. The remaining parameters were the same as the standard process.

[0170] Result analysis:

[0171] The change in the rotation direction causes a change in the melt flow pattern, which has a certain impact on the growth of twins, but the effect is limited. The deflection angle of the <100> twin is only about 10°, and the area reduction rate is about 25%, which is far lower than the effect of the method of the present invention. The dislocation density is 2.9×10 4 cm-2, the carrier concentration is 7.0×10 16 cm-3, the Hall mobility is 90 cm 2 / V·second (room temperature). The results show that simply changing the rotation direction is not enough to effectively suppress the twin extension.

[0172] To comprehensively evaluate the effectiveness of the method of the present invention, a systematic comparative analysis of the above-mentioned examples and comparative examples was conducted. The main evaluation indicators included: twin deflection angle, twin area reduction rate, dislocation density, carrier concentration, Hall mobility, and production efficiency.

[0173] Table 1. Performance comparison between examples and comparative examples

[0174]

[0175] The following conclusions can be drawn from the data in Table 1:

[0176] 1. The thermal field gradient induction method proposed in the present invention has a significant inhibitory effect on all types of twins. The twin deflection angles of Examples 1-4 are 25-45°, and the area reduction rate is 65-95%, which is much higher than that of the comparative examples.

[0177] 2. The twinning suppression effect is positively correlated with the magnitude of the horizontal temperature gradient. However, although an excessively large gradient (such as 25°C / cm in Comparative Example 2) can further improve the suppression effect, it will introduce more defects and reduce the overall quality of the crystal.

[0178] 3. Compared with the method of only reducing the growth rate (Comparative Example 3) or changing the rotation direction (Comparative Example 4), the method of the present invention achieves a significant twinning suppression effect while maintaining a relatively high production efficiency (80-90%), and has obvious technical and economic advantages.

[0179] 4. Different twin types respond differently to horizontal temperature gradients: -201 twins are most sensitive to temperature gradients, followed by 100 twins, and 010 twins are relatively insensitive. Therefore, in practical applications, the gradient parameters need to be adjusted based on the twin type.

[0180] 5. The method of the present invention can not only effectively suppress twinning, but also reduce dislocation density to a certain extent, increase carrier mobility, and comprehensively improve crystal quality.

[0181] In summary, the proposed method for inhibiting twin growth in gallium oxide crystals based on thermal field gradient induction introduces a specific horizontal temperature gradient during the crystal shouldering stage, effectively controlling the growth direction of twins, deflecting them toward the crystal edge and thereby suppressing their extension within the main crystal. This method offers advantages such as simplicity, high applicability, and no impact on production efficiency. It provides a new and effective approach for improving the quality of β-Ga2O3 crystals and has significant theoretical and practical value.

Claims

1. A method for inhibiting the growth of gallium oxide crystal twins based on thermal field gradient induction, characterized in that: The following steps are involved: Gallium oxide crystals are prepared using a guided mold growth device. After the crystal enters the shouldering stage, a horizontal temperature gradient field is established in the area above the mold by regulating the power of the heater partition or activating a local cooling device. According to the position and extension direction of the twin crystals in the seed crystal, the low temperature side of the horizontal temperature gradient field is set in the opposite direction of the extension direction of the twin crystals; Maintaining the horizontal temperature gradient field for a period of time until the twin growth direction is observed to deflect to the edge region of the low-temperature side of the crystal; When the twins are induced to the edge of the crystal or eliminated, the horizontal temperature gradient field is gradually reduced to restore normal equal-diameter growth conditions.

2. The method according to claim 1, characterized in that The guided mode growth device comprises: A multi-zone independently controlled heating system with independently controlled auxiliary heaters installed on both sides of the area above the mold. The auxiliary heaters have a power range of 0-2000W and a temperature control accuracy of ±1°C. An adjustable cooling device installed on one side of the area above the mold, the cooling device adopts water cooling or air cooling, the flow control range of the water cooling system is 0.5-5 liters per minute, and the flow control range of the air cooling system is 1-10 liters per minute; and The temperature monitoring system includes multiple thermocouples and infrared thermometers evenly distributed in the horizontal direction to monitor the temperature distribution near the growth interface in real time.

3. The method according to claim 1, characterized in that The horizontal temperature gradient field is 5-20°C per centimeter, and the specific gradient value is selected according to the type and severity of the twins: For slightly twinned crystals with an area share of less than 5%, the horizontal temperature gradient is 5-8°C per centimeter; For medium twins with an area share of 5-15%, the horizontal temperature gradient is 8-15°C per centimeter; For severe twinning with an area ratio greater than 15%, the horizontal temperature gradient is 15-20°C per centimeter.

4. The method according to claim 1, wherein The time for maintaining the horizontal temperature gradient field is determined according to the severity of the twinning: For slight twins with an area of ​​less than 5%, the maintenance time is 20-40 minutes; For medium twins with an area of ​​5-15%, the maintenance time is 40-80 minutes; For severe twins with an area ratio greater than 15%, the maintenance time is 80-120 minutes.

5. The method according to claim 1, wherein Establish the horizontal temperature gradient field by any of the following methods: Increase the power of the auxiliary heater on the high temperature side by 10-30% and reduce the power of the auxiliary heater on the low temperature side by 5-15%; or Keep the power of the auxiliary heater on the high-temperature side unchanged, start the cooling device on the low-temperature side, and gradually increase the cooling intensity from the minimum value to the set value.

6. The method according to claim 1, wherein The rate of gradually reducing the horizontal temperature gradient field is 1-5°C per centimeter per hour, which is selected according to the twin deflection effect: For cases where the deflection effect is significant, a faster rate of 3-5°C per centimeter per hour is used; For moderate deflection effects, a moderate rate of 2-3°C per centimeter per hour is used; For cases where the deflection effect is weaker, a slower rate of 1-2°C per centimeter per hour is used.

7. The method according to claim 1, characterized in that The gallium oxide crystals use high-purity β-Ga2O3 powder as raw material. The β-Ga2O3 powder has a purity of not less than 99.999%, an average particle size of 1-5 microns, and main impurity contents of: Si less than 2 ppm, Al less than 1 ppm, Fe less than 1 ppm, Ca less than 1 ppm, and the total amount of other metal impurities less than 5 ppm. The method also includes a raw material pretreatment step: calcining the β-Ga2O3 powder at 800±20°C for 4-6 hours to remove moisture and organic matter adsorbed on the surface.

8. The method according to claim 1, characterized in that The method further comprises the steps of crystal cooling and post-processing: After the crystal growth is completed, the temperature is lowered to 800°C at a rate of 2-5°C per minute; Cool from 800°C to room temperature at a rate of 1-2°C per minute; The crystal is placed in an annealing furnace and maintained at 950-1100°C for 6-24 hours for annealing to eliminate the thermal stress generated during the growth process.

9. The method according to claim 1, wherein: When used to suppress <010> oriented twinning, the horizontal temperature gradient is 10-15°C per centimeter, the gradient direction is perpendicular to the <010> direction, and the gradient maintenance time is 40-60 minutes; When used to suppress 〈100〉 oriented twinning, the horizontal temperature gradient is 8-12°C per centimeter, the gradient direction is perpendicular to the 〈100〉 direction, and the gradient maintenance time is 50-70 minutes; When used to suppress the <-201> oriented twinning, the horizontal temperature gradient is 12-18°C per centimeter, the gradient direction is perpendicular to the <-201> direction, and the gradient maintenance time is 30-50 minutes.

10. The method according to claim 1, characterized in that During the horizontal temperature gradient induction stage, the crystal growth rate is reduced to 65-85% of the original growth rate, and the crystal rotation speed is reduced to 4-9 revolutions per minute to reduce the influence of centrifugal force on melt flow; after the horizontal temperature gradient field is eliminated, the crystal growth rate is restored to 2-4 mm per hour, the crystal rotation speed is restored to 10-20 revolutions per minute, and isodiametric growth is continued to a predetermined length.

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