Thermal field structure for inhibiting volatilization and decomposition of gallium oxide, and growth device and growth method of gallium oxide crystal

Abstract

The invention provides a thermal field structure for inhibiting volatilization and decomposition of gallium oxide, and a growth device and a growth method of gallium oxide crystals, and belongs to the technical field of growth of the gallium oxide crystals. In order to effectively inhibit volatilization and decomposition of gallium oxide, a thermal field structure for crystal growth and a hearth of a growth furnace are effectively isolated, mutual airflow is effectively isolated, an effective space for volatilization, decomposition and diffusion of gallium oxide is greatly reduced by an independently closed thermal field structure space, and the thermal field structure is effectively closed; the positive air pressure can be formed in the closed thermal field space, volatilization and decomposition of gallium oxide in the gallium oxide crystal growth process can be greatly inhibited under the positive air pressure, the influence of volatilization and decomposition products on growth process control is avoided, and the control capability on the growth process is greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of gallium oxide crystal growth, and in particular to a thermal field structure for inhibiting the volatilization and decomposition of gallium oxide, a gallium oxide crystal growth device and a growth method. Background Art

[0002] Gallium oxide (β-Ga2O3) crystal is an ultra-wide bandgap semiconductor material with a bandgap width of up to 4.9eV, and is known as the "fourth generation semiconductor material". Compared with the third-generation wide bandgap semiconductor materials currently represented by SiC and GaN, gallium oxide crystals have the advantages of wider bandgap, higher breakdown field strength, and larger Baliga factor. In addition, gallium oxide crystals can take advantage of the melt growth method to greatly reduce the cost of crystal growth. Therefore, gallium oxide has become the preferred material for devices such as ultra-high voltage, ultra-high power devices and solar-blind detectors. Devices prepared using β-Ga2O3 as a substrate will have smaller on-resistance losses and higher conversion efficiency, and have great application prospects in the fields of new energy vehicles, rail transit, and 5G communications. Therefore, it is urgent to develop low-cost and high-quality gallium oxide crystal growth process methods.

[0003] Gallium oxide crystals can be grown using the melt method. Compared with the current popular third-generation semiconductor materials SiC and GaN, the crystal growth rate can be greatly improved, thereby reducing the cost of the crystal. However, the particularity of the gallium oxide material itself makes the growth process more difficult. During the growth process, gallium oxide is easily volatilized and decomposed at high temperatures. The specific reaction formula is as follows:

[0004]

[0005] The high-temperature volatilization and decomposition of gallium oxide will bring a series of problems to crystal growth. The volatile decomposition products such as GaO and Ga2O will adhere to the seed crystal, solid-liquid interface, crystal surface and other locations with the airflow, seriously affecting the crystal quality. At the same time, the metal gallium produced by the decomposition will corrode the crucible and the guide mold, which greatly increases the loss of iridium and increases the cost of crystal growth. In addition, the corroded metal iridium will enter the crystal to form inclusions, which will seriously affect the quality of the growing crystal and even cause the failure of crystal growth.

[0006] Existing methods for growing gallium oxide crystals, such as the guided mold method, the Czochralski method, and the casting method, cannot effectively suppress the problem of gallium oxide volatilization and decomposition. Since the guided mold method and the Czochralski method require seed crystal growth, there must be a channel in the center of the thermal field for the seed crystal to enter, so it is not possible to effectively form a closed space in the thermal field to suppress the decomposition of gallium oxide. In addition, since the existing melt method uses medium-frequency induction heating of the iridium crucible to heat the material growth, the furnace body shell of the growth equipment needs to increase the furnace body diameter as far away from the induction coil as possible in order to weaken the influence of electromagnetic induction. The increase in the volume space of the furnace body seriously increases the decomposition and volatilization of gallium oxide. For the casting method to grow gallium oxide crystals, since it is necessary to form a cold core in the middle area above the melt, it is also necessary to have an opening in the upper part of the thermal field. Therefore, the melt in the thermal field is directly connected to the growth furnace body space, and a gas flow loop will be formed in the thermal field and the growth furnace, which greatly increases the volatilization and decomposition of gallium oxide.

[0007] The existing related technologies cannot effectively inhibit the volatilization and decomposition of gallium oxide during the growth process of gallium oxide. Therefore, it is particularly important to develop a solution that can inhibit the volatilization and decomposition of gallium oxide. Summary of the invention

[0008] In view of this, the purpose of the present invention is to provide a thermal field structure for inhibiting the volatilization and decomposition of gallium oxide, a growth device and a growth method of gallium oxide crystals. The thermal field structure of the present invention forms an effective isolation with the growth furnace hearth, realizing effective isolation of the airflow between them, and the separate and closed thermal field space greatly reduces the effective space for the volatilization and decomposition of gallium oxide to diffuse.

[0009] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0010] The present invention provides a thermal field structure for inhibiting the volatilization and decomposition of gallium oxide, comprising:

[0011] A quartz barrel 9 and a crucible 10, wherein the crucible 10 is arranged inside the quartz barrel 9, the quartz barrel 9 is provided with a top sealing flange 5 and a bottom sealing flange 12, a support rod 11 is provided between the bottom of the quartz barrel 9 and the bottom sealing flange 12, an air outlet valve 1 is provided on the top sealing flange 5, and an air inlet valve 4 is provided on the bottom sealing flange 12;

[0012] The outer surface of the crucible 10 is provided with a thermal field insulation material 2;

[0013] The outer surface of the quartz barrel 9 is provided with a heating coil 3 .

[0014] Preferably, the crucible 10 is an iridium crucible.

[0015] Preferably, the ratio of the diameter to the depth of the crucible 10 is 0.5:1 to 20:1.

[0016] Preferably, the thermal field insulation material 2 is made of zirconium oxide and / or aluminum oxide.

[0017] Preferably, the thermal field insulation material 2 forms a temperature gradient of cold top and hot bottom, hot edges and cold middle, and the temperature gradient is: when the melt undergoes crystal growth, the radial temperature gradient of the melt is 3-20K / cm, and the axial temperature gradient is 5-30K / cm.

[0018] Preferably, the surface of the thermal field insulation material 2 has non-through holes.

[0019] Preferably, the heating coil 3 is a medium frequency induction coil.

[0020] The present invention also provides a gallium oxide crystal growth device, comprising the thermal field structure described in the above technical solution, a camera 6 and a furnace body 8, wherein the thermal field structure is located inside the furnace body 8, and a furnace body observation window 7 is provided on the outside of the furnace body 8.

[0021] The present invention also provides a method for growing gallium oxide crystals, using the growth device described in the above technical solution, comprising the following steps:

[0022] The gallium oxide raw material is placed in the crucible 10, the furnace body 8 is closed, and the gas outlet valve 1 is opened. The vacuum degree in the furnace body 8 is reduced to 1×10 -2 After Pa, close the outlet valve 1, open the inlet valve 4, and charge CO2;

[0023] Turning on the heating coil 3 to melt the gallium oxide raw material in the crucible 10 to obtain a melt;

[0024] The heating power of the heating coil 3 is reduced to allow the melt to undergo crystal growth, thereby obtaining the gallium oxide crystal.

[0025] Preferably, the gallium oxide raw material is a non-doped gallium oxide raw material or a doped gallium oxide raw material, and the doping elements in the doped gallium oxide raw material include one or more of Fe, Mg, Sn and Si.

[0026] The present invention provides a thermal field structure for inhibiting the volatilization and decomposition of gallium oxide, comprising: a quartz barrel 9 and a crucible 10, wherein the crucible 10 is arranged inside the quartz barrel 9, the quartz barrel 9 is provided with a top sealing flange 5 and a bottom sealing flange 12, a support rod 11 is provided between the bottom of the quartz barrel 9 and the bottom sealing flange 12, an air outlet valve 1 is provided on the top sealing flange 5, and an air inlet valve 4 is provided on the bottom sealing flange 12; a thermal field insulation material 2 or a mesoporous structure is provided on the outer surface of the crucible 10; and a heating coil 3 is provided on the outer surface of the quartz barrel 9.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] In order to effectively inhibit the volatilization and decomposition of gallium oxide, the present invention forms an effective isolation between the thermal field structure for crystal growth and the furnace of the growth furnace, and effectively cuts off the airflow between them. The space of the separately enclosed thermal field structure greatly reduces the effective space for the volatilization and decomposition and diffusion of gallium oxide. The thermal field structure is effectively sealed, and a positive pressure can be formed in the enclosed thermal field space. The decomposition of gallium oxide can be effectively inhibited under the positive pressure atmosphere, and the influence of the volatilization and decomposition products on the control of the growth process is avoided, which greatly improves the control ability of the growth process, and realizes the effective control of the atmosphere in a small area space, especially the control of the oxygen content in the thermal field area. In addition, oxygen can enter the thermal field area more directly, and the thermal field area The increase in the oxygen content in the domain can effectively inhibit the decomposition of gallium oxide. Since the entire thermal field structure is in the high-temperature area, the original partition structure of the high-temperature area and the low-temperature area of ​​the furnace shell has been changed. The change in the hot and cold zone structure has weakened the intensity of convection in the overall thermal field. The weakening of convection can further weaken the decomposition of gallium oxide, effectively solving the observation and temperature measurement problems caused by the volatilization and decomposition of gallium oxide, and greatly improving the repeatability and stability of crystal growth; and the inhibition of the decomposition and volatilization of gallium oxide at high temperature can greatly reduce the metallic gallium produced by the decomposition of the gallium oxide melt, alleviate the corrosion of the metallic gallium to the crucible, and reduce the cost of crystal growth. In addition, the quality of the grown gallium oxide crystals can be greatly increased, reducing defects such as iridium inclusions in the crystals.

[0029] Furthermore, in order to better enable oxygen to enter the gallium oxide melt, the present invention limits the diameter-to-depth ratio (ratio of diameter to depth) of the crucible 10 to 0.5:1-20:1. The entry of oxygen into the effective gallium oxide melt can effectively inhibit the decomposition of gallium oxide and slow down the corrosion of the crucible by the metal gallium produced by the decomposition. In particular, at the R corner of the crucible, the increase in the crucible diameter can increase the contact area between oxygen and the melt, greatly increasing the probability of oxygen entering the melt. At the same time, the reduction in the crucible depth also avoids the problem of gallium oxide decomposition and corrosion of the crucible caused by the oxygen diffusion distance.

[0030] Furthermore, in order to grow a reasonable thermal field gradient, different thermal conductivity insulation materials or a mesoporous structure are used in the crucible to form a temperature gradient of cold top and hot bottom, hot edge and cold middle, so that the nucleation growth initially occurs in the central area of ​​the upper surface of the melt, and the crystal grows stably by controlling the power of the heating coil 3;

[0031] Furthermore, the surface of the thermal field insulation material 2 has non-through holes, which can further improve the quality of the gallium oxide crystals.

[0032] The present invention also provides a method for growing gallium oxide crystals, which is applicable to non-doped gallium oxide raw materials and doped gallium oxide raw materials, and can grow semi-insulating, conductive gallium oxide crystals of any doping type, and is particularly applicable to the growth of conductive gallium oxide crystals such as tin-doped conductive type. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the structure of a gallium oxide crystal growth device;

[0034] Figure 2 This is a picture of the gallium oxide single crystal obtained in Example 1;

[0035] Figure 3 This is a picture of the gallium oxide single crystal obtained in Example 2;

[0036] Figure 4 This is a picture of a gallium oxide single crystal obtained in a comparative example;

[0037] In the figure, 1 is the outlet valve, 2 is the thermal field insulation material, 3 is the heating coil, 4 is the inlet valve, 5 is the top sealing flange, 6 is the camera, 7 is the furnace observation window, 8 is the furnace body, 9 is the quartz barrel, 10 is the crucible, 11 is the support rod, and 12 is the bottom sealing flange. DETAILED DESCRIPTION

[0038] The present invention provides a thermal field structure for inhibiting the volatilization and decomposition of gallium oxide, comprising:

[0039] A quartz barrel 9 and a crucible 10, wherein the crucible 10 is arranged inside the quartz barrel 9, the quartz barrel 9 is provided with a top sealing flange 5 and a bottom sealing flange 12, a support rod 11 is provided between the bottom of the quartz barrel 9 and the bottom sealing flange 12, an air outlet valve 1 is provided on the top sealing flange 5, and an air inlet valve 4 is provided on the bottom sealing flange 12;

[0040] The outer surface of the crucible 10 is provided with a thermal field insulation material 2;

[0041] The outer surface of the quartz barrel 9 is provided with a heating coil 3 .

[0042] Figure 1 The schematic diagram of the growth device of gallium oxide crystal is shown below. Figure 1 The thermal field structure for suppressing the volatilization and decomposition of gallium oxide provided by the present invention is described.

[0043] The thermal field structure for inhibiting the volatilization and decomposition of gallium oxide provided by the present invention comprises a quartz barrel 9, and the quartz barrel 9 is provided with a top sealing flange 5 and a bottom sealing flange 12. The present invention utilizes the top sealing flange 5 and the bottom sealing flange 12 to effectively isolate the thermal field structure for crystal growth from the furnace of the growth furnace, and effectively cuts off the airflow between them. The space of the separately sealed thermal field structure greatly reduces the effective space for the volatilization, decomposition and diffusion of gallium oxide, and effectively seals the thermal field structure, so that a positive pressure can be formed in the sealed thermal field space, and the volatilization and decomposition of gallium oxide itself during the growth of gallium oxide crystals can be greatly suppressed under the positive pressure atmosphere.

[0044] In the present invention, a heating coil 3 is provided on the outer surface of the quartz barrel 9 .

[0045] In the present invention, the heating coil 3 is preferably a medium frequency induction coil.

[0046] The thermal field structure for suppressing the volatilization and decomposition of gallium oxide provided by the present invention comprises a crucible 10 , and the crucible 10 is arranged inside the quartz barrel 9 .

[0047] In the present invention, the crucible 10 is preferably an iridium crucible.

[0048] In the present invention, the ratio of the diameter to the depth of the crucible 10 is preferably 0.5:1 to 20:1, specifically 1:1, 5:1, 10:1 or 15:1. In order to better enable oxygen to enter the gallium oxide melt, the present invention limits the diameter-to-depth ratio (diameter-to-depth ratio) of the crucible 10 to 0.5:1 to 20:1. The entry of oxygen into the gallium oxide melt can effectively inhibit the decomposition of gallium oxide and slow down the corrosion of the crucible by the metal gallium produced by the decomposition. In particular, at the R angle of the crucible, the increase in the diameter of the crucible can increase the contact area between oxygen and the melt, greatly increasing the probability of oxygen entering the melt. At the same time, the reduction in the depth of the crucible also avoids the problem of gallium oxide decomposition and corrosion of the crucible caused by the oxygen diffusion distance.

[0049] The thermal field structure for inhibiting the volatilization and decomposition of gallium oxide provided by the present invention comprises an outlet valve 1 , and the outlet valve 1 is arranged on a top sealing flange 5 .

[0050] The thermal field structure for inhibiting the volatilization and decomposition of gallium oxide provided by the present invention comprises an air intake valve 4 , and the air intake valve 4 is arranged on the bottom sealing flange 12 .

[0051] In the present invention, the outer surface of the crucible 10 is provided with a thermal field insulation material 2 .

[0052] In the present invention, the material of the thermal field insulation material 2 preferably includes zirconium oxide and / or aluminum oxide.

[0053] In the present invention, the thermal field insulation material 2 preferably forms a temperature gradient with cold top and hot bottom, hot edges and cold middle. The temperature gradient is further preferably: when the melt undergoes crystal growth, the radial temperature gradient of the melt is 3 to 20 K / cm, and the axial temperature gradient is 5 to 30 K / cm.

[0054] In the present invention, the surface of the thermal field insulation material 2 preferably has non-through holes, which do not destroy the effective isolation formed between the thermal field structure and the growth furnace hearth, and do not affect the separate closed thermal field structure space.

[0055] In the present invention, the diameter of the non-through hole is preferably 30 mm, and the depth is preferably 20 mm.

[0056] In the present invention, a hole is preferably provided at the center of the thermal field insulation material 2, and the main purpose of the hole is to facilitate nucleation at the center of the upper surface of the melt.

[0057] The present invention has no special limitation on the arrangement of the thermal field insulation material 2, which can be arranged according to the actual needs of the thermal field. In the present invention, the thermal field insulation material 2 is preferably arranged in the upper thermal field of the crucible 10, and the upper thermal field is the part above the center of the crucible 10.

[0058] In the present invention, the thermal field components of the thermal field structure are preferably installed horizontally and concentrically, and the crucible 10 is located at the center of the thermal field.

[0059] The present invention also provides a gallium oxide crystal growth device, comprising the thermal field structure described in the above technical solution, a camera 6 and a furnace body 8, wherein the thermal field structure is located inside the furnace body 8, and a furnace body observation window 7 is provided on the outside of the furnace body 8.

[0060] In the present invention, the camera 6 is used to monitor the melting condition of the gallium oxide raw material.

[0061] In the present invention, the furnace body 8 is preferably a single crystal furnace.

[0062] In the present invention, the growth device preferably further comprises a circulating cooling water device. The present invention has no special limitation on the specific configuration of the circulating cooling water device, and any configuration method familiar to those skilled in the art may be adopted.

[0063] The present invention has no special limitation on the preparation method of the thermal field structure and the growth device, and methods familiar to those skilled in the art may be used.

[0064] The present invention also provides a method for growing gallium oxide crystals, using the growth device described in the above technical solution, comprising the following steps:

[0065] The gallium oxide raw material is placed in the crucible 10, the furnace body 8 is closed, and the gas outlet valve 1 is opened. The vacuum degree in the furnace body 8 is reduced to 1×10 -2 After Pa, close the outlet valve 1, open the inlet valve 4, and charge CO2;

[0066] Turning on the heating coil 3 to melt the gallium oxide raw material in the crucible 10 to obtain a melt;

[0067] The heating power of the heating coil 3 is reduced to allow the melt to undergo crystal growth, thereby obtaining the gallium oxide crystal.

[0068] The gallium oxide raw material is placed in a crucible 10, the furnace body 8 is closed, and the gas outlet valve 1 is opened. The vacuum degree in the furnace body 8 is reduced to 1×10 -2 After Pa, the outlet valve 1 is closed, the inlet valve 4 is opened, and CO2 is charged.

[0069] In the present invention, the gallium oxide raw material is preferably a non-doped gallium oxide raw material or a doped gallium oxide raw material, and the doping elements in the doped gallium oxide raw material preferably include one or more of Fe, Mg, Sn and Si.

[0070] In the present invention, the non-doped gallium oxide raw material is preferably a 5N grade, sintered gallium oxide block.

[0071] In the present invention, in the thermal field structure, the top sealing flange 5 and the bottom sealing flange 12 can ensure the sealing of the entire thermal field structure.

[0072] The present invention preferably uses a mechanical pump to evacuate until the vacuum degree drops to 1×10 -2 After Pa.

[0073] In the present invention, the CO2 is preferably charged to make the air pressure in the closed hot field reach one atmosphere.

[0074] The present invention preferably opens the circulating cooling water device to cool the furnace body 8 .

[0075] After the CO2 is charged, the present invention turns on the heating coil 3 to melt the gallium oxide raw material in the crucible 10 to obtain a melt.

[0076] In the present invention, the heating power increasing rate of the heating coil 3 is preferably 200-800 W / h, specifically 200, 300, 400, 500, 600, 700 or 800 W / h.

[0077] During the melting process, an infrared thermometer is preferably used to monitor the temperature of the crucible 10 and the material block, and a camera 6 is used to monitor the melting of the gallium oxide material block. When the temperature is raised to 1600°C, the air inlet valve 4 is opened, and O2 is introduced into the closed thermal field until the concentration of O2 in the thermal field is preferably 0-20 vol% (specifically, it can be 2, 5, 10, 15 or 20 vol%). When the heating power is applied to the edge of the gallium oxide material block and micro-melting and liquid flow lines of the melt appear (observed through the furnace body observation window 7), the heating power is kept constant and the material block is waited for to melt. The melting process requires fine control. An infrared thermometer is used to monitor the temperature of the crucible 10 and the material block. When the heating power is applied to the gallium oxide material block to completely melt, the melt temperature is preferably 5-20°C higher than the melting point of the gallium oxide raw material (specifically, it can be 5, 10, 15 or 20°C), and is preferably maintained for 2-10h (specifically, it can be 2, 3, 4, 5, 6, 7, 8, 9 or 10h).

[0078] After obtaining the melt, the present invention reduces the heating power of the heating coil 3 to allow the melt to undergo crystal growth, thereby obtaining the gallium oxide crystal.

[0079] In the present invention, the rate of reduction of the heating power of the heating coil 3 is preferably 20 to 100 W / h (specifically, it can be 20, 30, 40, 50, 60, 70, 80, 90 or 100 W / h), so that the melt at the cold center position on the upper surface of the crucible 10 forms nuclei and grows. The thermal field structure on the upper part of the crucible 10 uses the thermal field insulation material 2 or the mesoporous structure to form a temperature gradient of upper cold and lower hot, edge hot and middle cold. During the crystal growth process, a slightly positive pressure state (preferably below 20 KPa) is maintained in the closed thermal field. The crystal temperature in the crucible 10 is preferably reduced to 1300 °C by using an infrared thermometer. When the temperature of the gallium oxide crystal is lower than 1000°C (specifically 1300, 1400 or 1500°C), argon is used to replace CO2 and O2 in the furnace; when the infrared thermometer measures that the temperature of the gallium oxide crystal is lower than 1000°C, the heating power of the heating coil 3 is increased at a power reduction rate of 200 to 500W / h (specifically 200, 300, 400 or 500W / h) to gradually cool the crystal. At this stage, since the crystal is always in the crucible 10, it is equivalent to in-situ annealing, which further improves the crystal quality. Then the crucible 10 is taken out of the heat field, so that the whole piece of gallium oxide crystal can be easily taken out.

[0080] After obtaining the gallium oxide crystals, the present invention preferably processes the gallium oxide crystals to obtain substrate sheets.

[0081] In the present invention, the processing is preferably cutting, grinding and polishing.

[0082] In the present invention, the crucible 10 is not corroded and can be reused.

[0083] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0084] Example 1

[0085] exist Figure 1 Gallium oxide crystals are grown in the growth apparatus shown.

[0086] Step 1: Install the heat field insulation material 2 and the crucible 10 (specifically, an iridium crucible) in the furnace body 8 (specifically, a crystal growth furnace, a single crystal furnace). The ratio of the diameter to the depth of the iridium crucible is 1:1. Put the 5N-grade gallium oxide block that has been pressed and sintered into the iridium crucible, install the top sealing flange 5 and the bottom sealing flange 12 of the heat field, and ensure the sealing of the entire heat field structure. The equipment uses the heating coil 3 (specifically, a medium-frequency induction coil) to heat the crucible 10. The construction of the heat field confirms that the heat field components are horizontal and concentrically installed. The crucible 10 is located in the center of the heat field. Close the door of the crystal growth furnace, open the exhaust valve 1, and use a mechanical pump to evacuate until the vacuum degree drops to 1×10 -2 After the temperature reaches 1000 Pa, close the outlet valve 1, open the inlet valve 4, fill with CO2 to make the air pressure in the closed hot field one atmosphere, and turn on the circulating cooling water device; use zirconia fiber bricks as the insulation material to form a temperature gradient of cold top and hot bottom, hot edge and cold middle (when the melt is undergoing crystal growth, the radial temperature gradient of the melt is 20K / cm, and the axial temperature gradient is 30K / cm), so that the nucleation growth initially occurs in the central area of ​​the upper surface of the melt;

[0087] Step 2: Turn on the heating device of the medium frequency induction coil, melt the raw materials in the crucible 10 at a heating power rate of 500W / h, monitor the temperature of the crucible 10 and the material block with an infrared thermometer, and monitor the melting of the gallium oxide material block with a high-temperature camera 6. When the temperature rises to 1600°C, open the air inlet valve 4, and introduce O2 into the closed thermal field so that the content of O2 in the closed thermal field is 2vol%. When the power is added to the edge of the gallium oxide material block and micro-melting and liquid flow lines of the melt appear, keep the power constant and wait for the material block to melt slowly. The melting process requires fine control. Use an infrared thermometer to monitor the temperature of the crucible 10 and the material block. When the power is added to the gallium oxide material block to completely melt, the melt temperature is 10°C higher than the melting point of gallium oxide and maintained for 2h. Since the thermal field structure is completely sealed, the space is effectively greatly reduced. In addition, the convection effect of the entire thermal field is significantly weakened, and the volatilization and decomposition of gallium oxide in the molten state is greatly reduced;

[0088] Step 3: Reduce the medium frequency induction power, slowly cool down at a rate of 50W / h, so that the melt at the cold center position on the upper surface of the crucible forms nuclei and grows, and the thermal field structure on the upper part of the crucible is formed by using insulation materials to form a temperature gradient of cold top and hot bottom, hot edge and cold middle. During the crystal growth process, maintain a slightly positive pressure state (20KPa) in the closed thermal field. When the crystal temperature in the crucible 10 drops to 1400°C using an infrared thermometer, argon is used to replace the CO2 and O2 gases in the furnace;

[0089] Step 4: When the infrared thermometer measures that the temperature of the gallium oxide crystal is lower than 1000°C, increase the intermediate frequency induction power rate to 300W / h to gradually cool the crystal to 800°C (at this stage, since the crystal is always in the crucible 10, it is equivalent to in-situ annealing of the crystal), and then remove the crucible 10 from the heat field, so that the entire gallium oxide single crystal can be easily taken out. It is observed that the single crystal is transparent and there is no iridium inclusion inside the crystal. After cutting, grinding and polishing, a single crystal substrate can be obtained. At the same time, the iridium crucible is not corroded and can be reused.

[0090] Example 2

[0091] exist Figure 1 The growth of gallium oxide crystals is carried out in the growth apparatus shown:

[0092] Step 1: Install the heat field insulation material 2 and the crucible 10 (specifically, an iridium crucible) in the furnace body 8 (specifically, a crystal growth furnace, a single crystal furnace). The ratio of the diameter to the depth of the iridium crucible is 1:1. Put the 5N-grade gallium oxide block that has been pressed and sintered into the iridium crucible, install the top sealing flange 5 and the bottom sealing flange 12 of the heat field, and ensure the sealing of the entire heat field structure. The equipment uses the heating coil 3 (specifically, a medium-frequency induction coil) to heat the crucible 10. The construction of the heat field confirms that the heat field components are horizontal and concentrically installed. The crucible 10 is located in the center of the heat field. Close the door of the crystal growth furnace, open the exhaust valve 1, and use a mechanical pump to evacuate until the vacuum degree drops to 1×10 -2 After Pa, close the outlet valve 1, open the inlet valve 4, fill with CO2 to make the air pressure in the closed hot field one atmosphere, and turn on the circulating cooling water device; the insulation material is zirconia fiber brick, the center of the zirconia fiber brick has a non-through hole, the size of the hole is 30mm in diameter and 20mm in depth, and a temperature gradient of cold on the top and hot on the bottom, hot on the edge and cold in the middle is formed when the melt is undergoing crystal growth (when the melt is undergoing crystal growth, the radial temperature gradient of the melt is 3K / cm, and the axial temperature gradient is 5K / cm), so that the nucleation growth initially occurs in the central area of ​​the upper surface of the melt;

[0093] Steps 2 to 4 are the same as those in Example 1.

[0094] Figure 2 This is a picture of the gallium oxide single crystal obtained in Example 1. Figure 3 This is a picture of the gallium oxide single crystal obtained in Example 2. It can be seen that due to the non-through holes in Example 2, the center of the melt has sufficient undercooling and a suitable gradient, and finally a high-quality single crystal is formed. And by comparing Examples 1 and 2, it can be seen that the gallium oxide single crystal obtained in Example 2 has fewer defects and higher quality.

[0095] Comparative Example

[0096] Growth of gallium oxide crystals in a growth apparatus:

[0097] Step 1: The growth device is the same as Example 1, except that the top sealing flange and the bottom sealing flange are not provided, and the growth device has an open structure.

[0098] Steps 2 to 4 are the same as in Example 1.

[0099] Figure 4 This is a picture of a gallium oxide single crystal obtained in a comparative example. It can be seen that due to the lack of a separate closed thermal field structure space during the melt growth process, gallium oxide volatilization and decomposition occurred, and ultimately no single crystal was formed, and the crystal was a mixed crystal.

[0100] In summary, the present invention greatly inhibits the volatilization and decomposition of gallium oxide itself during the crystal growth process, avoids the influence of the volatilization and decomposition products on the control of the growth process, greatly improves the ability to control the growth process, effectively solves the observation and temperature measurement problems caused by the volatilization and decomposition of gallium oxide, and greatly improves the repeatability and stability of crystal growth; the inhibition of the decomposition and volatilization of gallium oxide at high temperature can greatly reduce the metallic gallium generated by the decomposition of the gallium oxide melt, alleviate the corrosion of the metallic gallium to the crucible, and reduce the cost of crystal growth. In addition, the quality of the grown gallium oxide crystal can be greatly increased, and defects such as iridium inclusions in the crystal can be reduced.

[0101] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A thermal field structure for inhibiting the volatilization and decomposition of gallium oxide, characterized in that: include: A quartz barrel (9) and a crucible (10), wherein the crucible (10) is arranged inside the quartz barrel (9), the quartz barrel (9) is provided with a top sealing flange (5) and a bottom sealing flange (12), a support rod (11) is provided between the bottom of the quartz barrel (9) and the bottom sealing flange (12), an air outlet valve (1) is provided on the top sealing flange (5), and an air inlet valve (4) is provided on the bottom sealing flange (12); The outer surface of the crucible (10) is provided with a thermal field insulation material (2); The outer surface of the quartz barrel (9) is provided with a heating coil (3).

2. The thermal field structure according to claim 1, characterized in that: The crucible (10) is an iridium crucible.

3. The thermal field structure according to claim 1 or 2, characterized in that: The ratio of the diameter to the depth of the crucible (10) is 0.5:1 to 20:

1.

4. The thermal field structure according to claim 1, characterized in that: The material of the thermal field insulation material (2) includes zirconium oxide and / or aluminum oxide.

5. The thermal field structure according to claim 1, characterized in that: The thermal field insulation material (2) forms a temperature gradient of cold top and hot bottom, hot edges and cold middle. The temperature gradient is: when the melt undergoes crystal growth, the radial temperature gradient of the melt is 3-20K / cm, and the axial temperature gradient is 5-30K / cm.

6. The thermal field structure according to claim 4 or 5, characterized in that: The surface of the thermal field insulation material (2) has non-through holes.

7. The thermal field structure according to claim 1, characterized in that: The heating coil (3) is a medium frequency induction coil.

8. A gallium oxide crystal growth device, characterized in that: It comprises the thermal field structure according to any one of claims 1 to 7, a camera (6) and a furnace body (8), wherein the thermal field structure is located inside the furnace body (8), and a furnace body observation window (7) is provided on the outside of the furnace body (8).

9. A method for growing gallium oxide crystals, characterized in that: Utilizing the growth device of claim 8, comprising the following steps: The gallium oxide raw material is placed in a crucible (10), the furnace body (8) is closed, and the gas outlet valve (1) is opened. The vacuum degree in the furnace body (8) is reduced to 1×10 -2 After reaching Pa, the outlet valve (1) is closed, the inlet valve (4) is opened, and CO2 is charged; Turning on the heating coil (3) to melt the gallium oxide raw material in the crucible (10) to obtain a melt; The heating power of the heating coil (3) is reduced to allow the melt to undergo crystal growth, thereby obtaining the gallium oxide crystal.

10. The growth method according to claim 9, characterized in that: The gallium oxide raw material is a non-doped gallium oxide raw material or a doped gallium oxide raw material, and the doping elements in the doped gallium oxide raw material include one or more of Fe, Mg, Sn and Si.

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