Gallium oxide single crystal growth apparatus and method

Abstract

This application provides a gallium oxide single crystal growth apparatus and method. The apparatus includes a furnace body, an upper seed crystal rod passing through the upper cover, a lower seed crystal rod passing through the lower cover, and a spiral induction coil wound around the periphery of the furnace cylinder to provide a high-frequency alternating magnetic field. The induction coil includes a stabilizing coil and a levitation heating coil from top to bottom. The electromagnetic force generated by the stabilizing coil after energizing is opposite in direction to the electromagnetic force generated by the levitation heating coil after energizing. The two interact to stably levitate the levitation heat source placed in the furnace cylinder within the working area enclosed by the induction coil during operation. This method heats the levitation heat source using the induction coil, and then uses the levitation heat source to heat the feed rod to obtain a levitation melt. The seed crystal contacts the levitation melt and completes the growth of the gallium oxide single crystal, meeting the need for crucible-free growth of large-size gallium oxide single crystals larger than 2 inches.

Description

Technical Field

[0001] This application relates to the field of gallium oxide single crystal growth, and more particularly to a gallium oxide single crystal growth apparatus and method. Background Technology

[0002] Gallium oxide (β-Ga2O3), as a new generation of ultra-wide bandgap semiconductor material, has advantages such as a large bandgap (4.85 eV), high breakdown electric field strength (8 MV / cm), large Baliga quality factor, and stable physicochemical properties. Studies show that its Baliga's Figure of Merit (BFOM) is about 3400 times that of Si and about 10 times that of SiC. It can reduce the power loss of electronic devices during use and has significant application value in power devices, optoelectronic devices, and sensors. It is one of the important alternatives to wide bandgap semiconductor materials silicon carbide and gallium nitride.

[0003] Currently, conventional methods for growing gallium oxide (β-Ga2O3) single crystals include crucible-based processes and traditional crucible-free processes. Crucible-based processes include the Czochralski method, mold-guided method, Bridgman process, and casting method. These processes use crucibles made of the precious metal iridium, whose material cost is difficult to reduce. Furthermore, during gallium oxide single crystal growth, iridium crucibles are subject to corrosion and wear, further increasing production costs. More importantly, gallium oxide single crystals can be contaminated by iridium doping during growth, affecting crystal purity and consequently crystal performance. Traditional crucible-free processes, such as the optical floating zone method, while eliminating the need for precious metal crucibles, can only grow gallium oxide single crystals smaller than 2 inches, failing to meet the demands of large-volume, large-size industrial production.

[0004] In summary, to meet the industrialization needs of gallium oxide single crystals, it is urgent to develop a crucible-free growth process and equipment capable of growing large-size gallium oxide single crystals. Summary of the Invention

[0005] Based on this, and in response to the above requirements, the present invention proposes a crucible-free gallium oxide single crystal growth method and apparatus, which can be used to grow large-size gallium oxide single crystals of 2 inches or more.

[0006] The gallium oxide single crystal growth apparatus provided in this application embodiment includes: a gallium oxide single crystal growth apparatus, comprising:

[0007] The furnace body includes a furnace cylinder, an upper cover and a lower cover respectively disposed at both ends of the furnace cylinder. The upper cover is provided with a feeding channel and a first gas channel communicating with the interior of the furnace cylinder. The feeding channel is used to feed suspended heat source material into the furnace cylinder. The lower cover is provided with a second gas channel communicating with the interior of the furnace cylinder. In the working state, the first gas channel and the second gas channel serve as an inlet channel and an outlet channel, respectively, so as to form a stable gas atmosphere in the furnace body. Preferably, the first gas channel is the outlet channel and the second gas channel is the inlet channel.

[0008] An upper seed crystal rod is inserted through the upper cover, and the upper seed crystal rod is used to place gallium oxide rods;

[0009] A lower seed crystal rod is inserted through the lower cover, and the lower seed crystal rod is used to place gallium oxide seed crystals;

[0010] A spiral induction coil wound around the periphery of the furnace cylinder is used to provide a high-frequency alternating magnetic field. The induction coil includes a stabilizing coil and a suspending heating coil from top to bottom. When the stabilizing coil is energized, it generates a downward first electromagnetic force. When the suspending heating coil is energized, it generates an upward second electromagnetic force. The first and second electromagnetic forces interact to ensure that the suspended heat source placed in the furnace cylinder is stably suspended in the working area enclosed by the induction coil during operation.

[0011] Preferably, the winding direction of the stabilizing coil is opposite to that of the levitation heating coil, so that in the working state, the levitation heat source located in the working area is subjected to electromagnetic forces from the stabilizing coil and the levitation heating coil in opposite directions, which counterbalance each other, so as to maintain the levitation heat source stably suspended in the working area, without moving up and down due to uneven force.

[0012] Preferably, the metal conduit winding the induction coil has a hollow internal structure, and the metal conduit winding the stabilizing coil and the metal conduit winding the levitation heating coil are interconnected. In operation, coolant can be introduced into the hollow structure of the induction coil to maintain normal operation and prevent damage even when the temperature rises due to high-power energization. Furthermore, the interconnection between the metal conduit winding the stabilizing coil and the metal conduit winding the levitation heating coil allows for the continuous flow of coolant throughout the induction coil, with only one inlet and one outlet.

[0013] Preferably, the levitation heating coil includes a heating coil and a levitation coil arranged from top to bottom. The heating coil is wound in a cylindrical shape, and the levitation coil is wound in an inverted conical shape. The semi-cone angle β of the levitation coil is set within the range of 0° < β ≤ 90°. In operation, the main function of the heating coil is to continuously heat the levitation heat source while providing an upward second electromagnetic force, thus ensuring the continuous melting of the gallium oxide rod. The main function of the levitation coil is to continuously provide an upward second electromagnetic force to the levitation heat source, ensuring its stable levitation. Furthermore, with the same number of turns and vertical spacing, the inverted conical levitation coil provides a greater electromagnetic force than the cylindrical coil. The inverted conical levitation coil also allows the shape of the levitation heat source to be controlled in an inverted conical shape, facilitating faster flow of the molten gallium oxide rod onto the seed crystal, and making it easier to control the contact area with the seed crystal, thus accelerating and optimizing the formation process of gallium oxide single crystals.

[0014] Preferably, the number of turns of the stabilizing coil is N1, the number of turns of the heating coil is N2, and the number of turns of the levitation coil is N3, wherein N1≤N2 and N1≤N3. The more turns the coil has, the stronger the magnetic field and the greater the electromagnetic force generated when energized. In operation, since the first electromagnetic force provided by the stabilizing coil is downward, in the same direction as the gravity of the levitation heat source, the number of turns of the stabilizing coil must be less than the number of turns of the levitation coil to maintain a stable levitation state of the heat source. Furthermore, since the direction of the magnetic field provided by the stabilizing coil is opposite to the direction of the magnetic field of the heating coil, the number of turns of the stabilizing coil must be less than the number of turns of the heating coil to ensure the heating effect of the heating coil.

[0015] Preferably, the vertical turn spacing of the stabilizing coil is d1, the vertical turn spacing of the heating coil is d2, and the vertical turn spacing of the levitation coil is d3, where d1 ≥ d2 and d1 ≥ d3. The smaller the vertical turn spacing of the coils, the greater the magnetic field strength and electromagnetic force generated when energized. In operation, since the first electromagnetic force provided by the stabilizing coil is downward and in the same direction as the gravity of the levitation heat source, to maintain the levitation heat source in a stable levitation state, the vertical turn spacing of the stabilizing coil needs to be greater than that of the levitation coil. Furthermore, since the magnetic field direction provided by the stabilizing coil is opposite to that of the heating coil, to ensure the heating effect of the heating coil, the vertical turn spacing of the stabilizing coil needs to be greater than that of the heating coil.

[0016] Preferably, d2 ≥ d3. The smaller the vertical spacing between the turns of the suspension coil, the greater the levitation force (i.e., the second electromagnetic force) provided to the suspension heat source, and the easier it is for the suspension heat source to form an inverted cone shape.

[0017] Preferably, the first gas channel is an outlet channel, and the second gas channel is an inlet channel. During operation, an upward-flowing gas channel is formed, allowing the lower-temperature gas in the inlet channel to preferentially contact the grown gallium oxide single crystal. This accelerates the growth rate of the gallium oxide single crystal. Furthermore, since the gallium oxide rod and the suspended heat source region require high temperatures during crystal growth, the upward-flowing gas flow gradually raises the gas temperature, thereby mitigating the impact of gas temperature on the temperature of the gallium oxide rod and the suspended heat source region.

[0018] Preferably, the furnace cylinder is a sapphire cylinder or a quartz cylinder. Since the induction coil is wound around the outside of the furnace cylinder, and the heating effect during the heating process of the suspended heat source is achieved by infrared light, in terms of the selection of furnace cylinder material, this embodiment of the application preferentially selects a material that is transparent to the infrared band, that is, the furnace cylinder material allows infrared light to pass through and does not absorb or reflect most of the infrared light. In addition, the furnace cylinder material has a high melting point and does not react with the gas introduced during the operation, ensuring the stability of the gallium oxide single crystal growth process.

[0019] Preferably, the diameter of the gallium oxide single crystal grown using the gallium oxide single crystal growth apparatus is D, and the inner diameter of the furnace cylinder is within the range of 1.2D-3D, thereby providing sufficient space for the generation of gallium oxide single crystals.

[0020] This invention also discloses a gallium oxide single crystal growth method, using the gallium oxide single crystal growth apparatus described above, the growth method comprising:

[0021] A gallium oxide rod is mounted on the upper seed crystal rod, and a gallium oxide seed crystal is mounted on the lower seed crystal rod.

[0022] A first flowing gas is introduced into the furnace cylinder through the first gas channel and the second gas channel to form a stable flowing atmosphere in the furnace cylinder;

[0023] An alternating current of a preset frequency and a preset magnitude is passed through the induction coil to form a high-frequency alternating magnetic field of target frequency and target power in the working area enclosed by the induction coil within the furnace drum.

[0024] Suspended heat source material is fed into the furnace cylinder through the feeding channel. Under the action of the high-frequency alternating magnetic field, the stabilizing coil generates a downward first electromagnetic force after being energized, and the suspended heating coil generates an upward second electromagnetic force after being energized. The first and second electromagnetic forces interact to melt the suspended heat source material in the working area to obtain a suspended heat source. The suspended heat source is stably suspended in the working area. The suspended heat source material is a conductive material. The working temperature of the suspended heat source is T1, and the melting point of the gallium oxide rod is T2, where T1 > T2.

[0025] Entering the feeding stage: The upper seed crystal rod descends at a first rate V1, bringing the bottom end of the gallium oxide rod close to and in contact with the suspended heat source, causing the gallium oxide rod to melt. The upper seed crystal rod continues to descend until the molten gallium oxide rod material completely envelops the suspended heat source, forming a suspended melt (i.e., the core of the suspended melt is the suspended heat source in a molten state, and the outer layer is the molten gallium oxide rod material). The suspended melt remains suspended under the action of the high-frequency alternating magnetic field.

[0026] Stop the flow of the first flowing gas and start the flow of the second flowing gas to form a stable flowing atmosphere;

[0027] Entering the crystal growth stage: The lower seed crystal rod is raised so that the top of the gallium oxide seed crystal approaches and contacts the bottom of the suspended melt. The descent rate of the lower seed crystal rod is adjusted so that the gallium oxide single crystal begins to grow along the top of the gallium oxide seed crystal until the grown gallium oxide single crystal reaches the target size. The lower seed crystal rod is then lowered again until the generated gallium oxide crystal separates from the suspended melt, at which point the upper seed crystal rod stops descending. During the growth of the gallium oxide single crystal, the upper seed crystal rod continues to descend so that the gallium oxide rod continues to melt and maintain the state of the suspended melt. The second flowing gas is continuously introduced into the furnace cylinder.

[0028] Entering the shutdown stage: Maintain the suspended melt state and continue to suspend, stop the supply of the second flowing gas, start the supply of the first flowing gas, until the molten gallium oxide rod material surrounding the suspended heat source in the suspended melt volatilizes and decomposes, stop the supply of the first flowing gas, start the supply of the second flowing gas, and gradually reduce the power of the induction coil to zero, so that the suspended heat source oxidizes and cools down to form a solid block and falls; when the furnace temperature drops to the target temperature, stop the supply of the second flowing gas.

[0029] Preferably, the crystal growth stages include a seeding stage, a necking stage, a shoulder formation stage, a constant diameter stage, and a finishing stage, with each stage proceeding as follows:

[0030] During the seeding stage: the lower seed rod rises at a second rate V2, bringing the top of the gallium oxide seed close to and below the suspended melt;

[0031] Necking stage: The lower seed crystal rod descends at a third rate V3, causing the gallium oxide single crystal to begin growing along the top of the gallium oxide seed crystal and forming a narrow neck. During this process, the upper seed crystal rod continues to descend to melt the gallium oxide rod and maintain the state of the suspended melt.

[0032] Shoulder-forming stage: The lower seed crystal rod descends at a fourth rate V4, and / or the power of the induction coil is reduced, so that the diameter of the grown gallium oxide single crystal increases. During this process, the upper seed crystal rod continues to descend to melt the gallium oxide rod and maintain the state of the suspended melt, where V4 < V3.

[0033] Equal diameter stage: After the diameter of the grown gallium oxide single crystal expands to the target size, the lower seed crystal rod descends at a fifth rate V5 to maintain the diameter of the grown gallium oxide single crystal at the target size. During this process, the upper seed crystal rod continues to descend to melt the gallium oxide rod and maintain the state of the suspended melt, where V5 < V4.

[0034] Final stage: When the length of the grown gallium oxide single crystal reaches the target size, the lower seed crystal rod descends at a sixth rate V6, and / or the power of the induction coil is increased, so that the diameter of the grown gallium oxide single crystal gradually shrinks until it detaches from the suspended melt. When the gallium oxide single crystal detaches from the suspended melt, the upper seed crystal rod stops descending, where V6 > V5.

[0035] Preferably, the first flowing gas is an inert gas, and the second flowing gas is a mixture of oxygen and other gases, wherein the other gases include one or more of carbon dioxide, argon, and nitrogen, and the oxygen content in the second flowing gas is X, where 0 < X ​​≤ 100%.

[0036] Preferably, the flow rate of the first flowing gas is equal to the flow rate of the second flowing gas.

[0037] Preferably, the suspended heat source material has good electrical conductivity, a boiling point higher than the melting point of the gallium oxide rod, low reactivity or low solid solution limit between the suspended heat source material and the molten gallium oxide rod material, and does not change the electrical type of the gallium oxide single crystal in the molten state.

[0038] Preferably, when the electrical type of the gallium oxide single crystal is n-type, the suspended heat source material is Sn, Si, Ta, or Nb; when the electrical type of the gallium oxide single crystal is semi-insulating, the suspended heat source material is Fe or Mg; when the electrical type of the gallium oxide single crystal is unintentionally doped, the suspended heat source material is Ga.

[0039] Preferably, the operating temperature T1 of the suspended heat source is within the range of 1750℃-1900℃.

[0040] Preferably, the diameter of the side of the suspended heat source in contact with the gallium oxide rod is D1, the diameter of the gallium oxide rod is D2, and the diameter of the gallium oxide single crystal is D3, wherein D1≥D2 and D3≥D2.

[0041] Preferably, the suspended heat source is inverted conical in shape, with a base diameter of D1, a weight of m, and a density of ρ.

[0042] Where D1 = (24m × tanβ / (πρ))^(1 / 3);

[0043] Alternatively, the suspended heat source may be spherical or cylindrical in shape.

[0044] Preferably, the weight m of the suspended heat source is within 1g-100g.

[0045] Preferably, during operation, the frequency of the induction coil is within 1kHz-500kHz, the power of the induction coil is within 1kW-2000kW, and the frequency of the induction coil remains constant during operation.

[0046] Preferably, during the equal diameter stage, the descent rate V5 of the lower seed crystal rod is within 0.5 mm / h to 50 mm / h to ensure that the diameter of the grown gallium oxide single crystal is uniform.

[0047] Preferably, the diameter of the gallium oxide single crystal is within 2 inches to 8 inches.

[0048] The crucible-free gallium oxide single crystal growth method and apparatus proposed in this application are no longer limited by the high cost of precious metal crucibles, and also avoid the contamination of gallium oxide single crystals by precious metal impurities. At the same time, they are no longer limited by the heating light source of the optical floating zone method, and can meet the growth requirements of large-size gallium oxide single crystals of 2 inches and above.

[0049] Specifically, the spiral induction coils wound around the periphery of the furnace cylinder provide a high-frequency alternating magnetic field when energized. The interaction between the downward first electromagnetic force generated by the energized stabilizing coil and the upward second electromagnetic force generated by the levitation heating coil allows the suspended heat source material, fed into the furnace cylinder through the feeding channel above the furnace cylinder, to stably suspend within the working area enclosed by the induction coils. Furthermore, the levitation heating coils heat the suspended heat source material, melting it to form a suspended heat source, which remains in a molten state throughout the crystal growth process. During crystal growth, the molten suspended heat source is used as a heat source to contact the gallium oxide rod mounted on the upper seed crystal rod, heating the gallium oxide rod until it melts and completely encapsulates the suspended heat source, forming a suspended melt. This suspended melt has a molten core as the suspended heat source and an outer layer of molten gallium oxide material. After obtaining the suspended melt, the upper seed crystal rod continues to descend, allowing the gallium oxide seed crystal to continue melting. Simultaneously, the lower seed crystal rod rises, bringing the gallium oxide seed crystal into contact with the suspended melt and initiating the crystal growth process. This crystal growth process is similar to that of the zone melting method, continuing until a gallium oxide single crystal of the target size is obtained, at which point the furnace is shut down. Since the molten gallium oxide rod material is easily volatilized in an oxygen-deficient atmosphere, this application first creates an oxygen-deficient atmosphere within the furnace barrel. This allows the molten gallium oxide rod material on the outer layer of the suspended melt to volatilize. Furthermore, because the suspended heat source material can oxidize to form oxide solids in an oxidizing atmosphere, and oxides have poor conductivity, the electromagnetic levitation force decreases, allowing it to gradually descend to the bottom of the furnace barrel for easy removal.

[0050] The embodiments of this application can adjust the size of the suspended heat source within the allowable range of the heating power borne by the induction coil, thereby generating gallium oxide single crystal rods of different sizes as needed, and can generate large-sized gallium oxide single crystal rods. Attached Figure Description

[0051] Figure 1 This is a cross-sectional view of a gallium oxide single crystal growth apparatus in one embodiment;

[0052] Figure 2 This is a flowchart of a gallium oxide single crystal growth method in one embodiment;

[0053] Figure 3 This is a flowchart of a gallium oxide single crystal growth method in one embodiment;

[0054] Figure 4 This is a cross-sectional schematic diagram of the gallium oxide single crystal growth apparatus during operation in one embodiment;

[0055] Figure 5 This is a schematic diagram of the current direction of the induction coil during the gallium oxide single crystal growth process in one embodiment.

[0056] Labeling Explanation: 11. Furnace cylinder; 12. Top cover; 13. Feeding channel; 14. First gas channel; 15. Bottom cover; 16. Second gas channel; 2. Upper seed crystal rod; 21. Gallium oxide rod; 22. Suspended melting zone; 23. Molten pool; 3. Lower seed crystal rod; 31. Gallium oxide seed crystal; 4. Induction coil; 41. Stabilizing coil; 42. Heating coil; 43. Suspended coil; 5. Suspended heat source; 6. Gallium oxide single crystal. Detailed Implementation

[0057] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0058] As described in the background section, existing methods for growing gallium oxide single crystals all have shortcomings. Therefore, this application provides a crucible-free gallium oxide single crystal growth method and apparatus that cleverly combines the advantages of zone melting and suspension melting processes. It is no longer limited by the high cost of precious metal crucibles in existing crucible-requiring growth processes, and also avoids the contamination of gallium oxide single crystals by precious metal impurities. At the same time, it is no longer limited by the size of gallium oxide single crystals in existing crucible-free processes, such as the limitation of heating light source in the optical floating zone method, and can meet the growth requirements of large-size gallium oxide single crystals of 2 inches and above.

[0059] Specifically, such as Figure 1 The diagram shown is a cross-sectional view of the gallium oxide single crystal growth apparatus disclosed in this application. The growth apparatus structure includes:

[0060] The furnace body includes a furnace cylinder 11, an upper cover 12 and a lower cover 15 respectively disposed at the upper and lower ends of the furnace cylinder 11. The upper cover 12 is provided with a feeding channel 13 and a first gas channel 14 communicating with the interior of the furnace cylinder 11. The feeding channel 13 is used to feed suspended heat source material into the furnace cylinder 11. The lower cover 15 is provided with a second gas channel 16 communicating with the interior of the furnace cylinder 11. Furthermore, the first gas channel 14 and the second gas channel 16 provide a stable gas atmosphere during the growth of gallium oxide single crystals; that is, one serves as an inlet channel and the other as an outlet channel. In order to improve the growth efficiency of gallium oxide single crystals and to avoid the influence of impurities in the furnace cylinder on the quality of gallium oxide single crystals, this application preferably uses the second gas channel 16 as an inlet channel and the first gas channel 14 as an outlet channel, that is, in the actual production process, a bottom-up flowing gas atmosphere is formed in the furnace cylinder.

[0061] Furthermore, since the induction coil is wound around the outside of the furnace cylinder, and the heating effect during the heating of the suspended heat source is achieved by infrared light, this embodiment of the application prioritizes the selection of a material that is transparent to the infrared band. That is, the furnace cylinder material allows infrared light to pass through without absorbing or reflecting most of it. Additionally, this furnace cylinder material has a high melting point and does not react with the gas introduced during operation, ensuring the stability of the gallium oxide single crystal growth process. In this embodiment, the furnace cylinder 11 is preferably a sapphire cylinder or a quartz cylinder.

[0062] Furthermore, the diameter of the gallium oxide single crystal grown using this gallium oxide single crystal growth apparatus is D, and the inner diameter of the furnace cylinder is within the range of 1.2D-3D. That is, the inner diameter of the furnace cylinder must be larger than the diameter of the gallium oxide single crystal to allow sufficient space for high-temperature expansion under high-temperature operating conditions. Moreover, since a stable flow atmosphere must be maintained inside the furnace cylinder throughout the gallium oxide growth process, to allow sufficient space for gas passage and prevent gas flow from being blocked by the crystal inside the furnace, causing an explosion, the inner diameter of the furnace cylinder must also be larger than the diameter of the gallium oxide single crystal.

[0063] The growth apparatus also includes an upper seed crystal rod 2 inserted through the upper cover 12, the upper seed crystal rod 2 being used to hold gallium oxide rods. The gallium oxide rods used to grow gallium oxide single crystals are generally polycrystalline rods with irregular crystal order arrangements; in this application, they can be polycrystalline ceramic rods formed by pressing and sintering gallium oxide powder. In actual production, conventional methods can be used to install the gallium oxide rods onto the upper seed crystal rod 2, such as snap-fitting, threaded connection, or clamping with a clamping mechanism, as long as the stability of the rods is maintained during the gallium oxide single crystal growth process.

[0064] A lower seed crystal rod 3 is inserted through the lower cover 15, and the lower seed crystal rod 3 is used to place the gallium oxide seed crystal. The electrical properties of the generated gallium oxide single crystal are affected by the electrical properties of the gallium oxide seed crystal and the impurities doped in the gallium oxide rod. In actual production, it is necessary to select a gallium oxide seed crystal with the same electrical properties as the gallium oxide single crystal to be generated. The method of mounting the gallium oxide seed crystal on the lower seed crystal rod 3 can be the same as the method of mounting the gallium oxide rod on the upper seed crystal rod 2, or it can be different, as long as the stability of the gallium oxide seed crystal is maintained during the growth of the gallium oxide single crystal.

[0065] A spiral induction coil 4, wound around the periphery of the furnace cylinder 11, is used to provide a high-frequency alternating magnetic field. The induction coil 4 includes a stabilizing coil and a suspending heating coil from top to bottom. When the stabilizing coil is energized, it generates a downward first electromagnetic force F1, and when the suspending heating coil is energized, it generates an upward second electromagnetic force F2. The first and second electromagnetic forces interact to ensure that the suspended heat source placed in the furnace cylinder is stably suspended in the working area enclosed by the induction coil during operation.

[0066] In actual production, the magnitude of the second electromagnetic force F2 must be equal to the sum of the gravity G of the suspended heat source and the magnitude of the first electromagnetic force F1 to maintain the suspended heat source in a suspended state within the working area. The first electromagnetic force F1 provided by the stabilizing coil can be used to stabilize and limit the position of the suspended heat source, preventing it from swinging up and down during operation.

[0067] It is understandable that the function of the levitation heating coil is not only to provide the second electromagnetic force F2, but also to provide the thermal energy to heat the levitation heat source.

[0068] In this embodiment, the winding direction of the stabilizing coil is opposite to that of the levitation heating coil, so that when the heat source located in the working area is in the working state, the electromagnetic forces from the stabilizing coil and the levitation heating coil are opposite in direction and mutually counterbalance each other, so as to maintain the levitation heat source stably suspended in the working area and prevent it from moving up and down due to uneven force.

[0069] Furthermore, in other embodiments, the suspended heating coil includes a heating coil and a suspension coil arranged from top to bottom, such as... Figure 5As shown, the induction coil 4 is divided from top to bottom into an uppermost stabilizing coil 41, a middle heating coil 42, and a lower levitation coil 43. The stabilizing coil 41 is preferably wound in a cylindrical shape, the heating coil 42 is also wound in a cylindrical shape, and the levitation coil 43 is wound in an inverted conical shape. The semi-cone angle β of the levitation coil is set within the range of 0° < β ≤ 90°. Since the current direction in the stabilizing coil 41 needs to be opposite to the current direction in the heating coil 42 and the levitation coil 43 during operation, to reduce the need for multiple current input structures, the winding direction of the stabilizing coil 41 in this embodiment is opposite to the winding direction of the heating coil 42 and the levitation coil 43.

[0070] In operation, the heating coil primarily provides an upward second electromagnetic force to the suspended heat source while continuously heating it to ensure the continuous melting of the gallium oxide rod. The suspension coil, on the other hand, continuously provides an upward second electromagnetic force to stabilize the suspended heat source. Furthermore, with the same number of turns and vertical spacing, the inverted conical suspension coil provides a greater electromagnetic force than the cylindrical one. The inverted conical shape also allows the suspended heat source to be controlled in an inverted conical shape, facilitating faster flow of the molten gallium oxide rod onto the seed crystal. The inverted conical shape also guides the flow path of the molten gallium oxide rod, making the contact area between the molten gallium oxide rod and the seed crystal easier to control and thus accelerating and optimizing the formation of gallium oxide single crystals.

[0071] Understandably, during the growth of gallium oxide single crystals, the role of the suspended heat source is primarily to heat and melt the gallium oxide ingot. The shape of the suspended heat source can be arbitrary, as long as the surface lines are smooth and can smoothly allow the molten gallium oxide ingot material to interact with the gallium oxide seed crystal or molten pool 23 (see...). Figure 4 Contact is sufficient. In other examples, the shape of the suspended heat source can be cylindrical, spherical, ellipsoidal, etc. Correspondingly, the shape of the suspended heat source is controlled by the winding shape of the suspended coil. When the suspended heat source is cylindrical, the suspended coil is wound cylindrically, that is, the semi-cone angle β of the suspended coil is 90°. Similarly, when the suspended heat source is spherical, the suspended coil is wound spherically, that is, the winding diameter of the suspended coil gradually increases from the upper end to the middle end and from the lower end to the middle end. This embodiment does not provide many examples of the winding shape of the suspended coil; it is sufficient to adjust the winding shape of the suspended coil adaptively according to the shape of the suspended heat source.

[0072] Specifically, the stabilizing coil 41 has N1 turns, the heating coil 42 has N2 turns, and the levitation coil 43 has N3 turns, where N1 ≤ N2 and N1 ≤ N3. The more turns the coil has, the stronger the magnetic field and electromagnetic force generated when energized. In operation, since the first electromagnetic force provided by the stabilizing coil is downwards, in the same direction as the gravity of the levitation heat source, the number of turns in the stabilizing coil must be less than the number of turns in the levitation coil to maintain a stable levitation state. Furthermore, since the magnetic field provided by the stabilizing coil is opposite to the magnetic field of the heating coil, the number of turns in the stabilizing coil must be less than the number of turns in the heating coil to ensure the heating effect of the heating coil.

[0073] Furthermore, the vertical turn spacing of the stabilizing coil 41 is d1, the vertical turn spacing of the heating coil 42 is d2, and the vertical turn spacing of the levitation coil 43 is d3, where d1 ≥ d2 and d1 ≥ d3. The smaller the vertical turn spacing of the coils, the greater the magnetic field strength and electromagnetic force generated when energized. In operation, since the first electromagnetic force provided by the stabilizing coil is downward and in the same direction as the gravity of the levitation heat source, the vertical turn spacing of the stabilizing coil needs to be greater than that of the levitation coil to maintain a stable levitation state. Also, since the magnetic field provided by the stabilizing coil is in the opposite direction to that of the heating coil, the vertical turn spacing d1 of the stabilizing coil needs to be greater than that of the heating coil to ensure the heating effect of the heating coil.

[0074] Furthermore, the smaller the vertical spacing between the turns of the suspension coil, the greater the levitation force (i.e., the second electromagnetic force) provided to the suspension heat source, and the easier it is for the suspension heat source to form an inverted cone shape. In the embodiments of this application, d2≥d3 is preferred.

[0075] It should be noted that the number of turns N3 and the vertical spacing d3 of the levitation coil are strongly correlated with the weight of the levitation heat source. The weight of the levitation heat source is related to the diameter of the gallium oxide single crystal to be formed; that is, the larger the diameter of the gallium oxide single crystal, the heavier the levitation heat source, the larger the number of turns N3 of the levitation coil, and the smaller the vertical spacing d3. Furthermore, the number of turns N2 and the vertical spacing d2 of the heating coil are also strongly correlated with the weight of the levitation heat source. The heavier the levitation heat source, the greater the thermal energy and power required to melt the levitation heat source material, the larger the number of turns N2 of the heating coil, and the smaller the vertical spacing d2.

[0076] In this embodiment, there is no absolute relationship between the number of turns N3 of the levitation coil and the number of turns N2 of the heating coil. Specifically, when the size of the gallium oxide single crystal to be generated is relatively small, the weight of the levitation heat source is also relatively small, and a large levitation force is not required. In this case, N3 ≤ N2. When the size of the gallium oxide single crystal to be generated is relatively large, the weight of the levitation heat source is also relatively large, and a strong levitation force is required. In this case, N3 ≥ N2 may exist.

[0077] Furthermore, in this embodiment, the metal pipe winding the induction coil has a hollow structure, and the metal pipe winding the stabilizing coil and the metal pipe winding the levitation heating coil are interconnected. During operation, coolant (such as cooling water) can be introduced into the hollow structure of the induction coil to maintain normal operation without damage even when the temperature rises due to high-power energization. Moreover, since the metal pipe winding the stabilizing coil and the metal pipe winding the levitation heating coil are interconnected, only one inlet and one outlet are needed to introduce coolant into the entire induction coil, allowing for continuous flow of coolant in and out of the metal pipes.

[0078] It should be noted that, in order to conveniently control the growth process of gallium oxide single crystals, it is also necessary to obtain timely information on the growth status of gallium oxide single crystals within the furnace cylinder 11. Therefore, in other embodiments, the gallium oxide single crystal growth apparatus further includes:

[0079] An observation window is set on the outer wall of the furnace cylinder to observe the crystal growth state inside the furnace cylinder;

[0080] Temperature and pressure sensors installed inside the furnace cylinder are used to understand and record the temperature and gas pressure inside the furnace cylinder, so as to adjust the gas atmosphere inside the furnace cylinder in real time. The temperature and pressure sensors can be installed on the inner wall of the furnace cylinder, or on the side of the upper or lower cover near the inner wall of the furnace cylinder, or in the air inlet and / or air outlet channels. This embodiment does not limit this.

[0081] Weight sensors and other components installed on the upper and lower seed crystal rods are used to provide feedback on the consumption of the material rod and the growth of the crystal during the gallium oxide single crystal growth process.

[0082] In addition, it includes a control system for receiving temperature signals, gas pressure signals, weight signals of the material bar and / or gallium oxide single crystal inside the furnace, and adaptively adjusting various parameters in the growth process of gallium oxide single crystal to ensure smooth growth of gallium oxide single crystal.

[0083] The gallium oxide single crystal growth apparatus proposed in this application does not require a precious metal crucible, thus eliminating the high cost limitation of precious metal crucibles and avoiding contamination of the gallium oxide single crystal by precious metal impurities. It also eliminates the limitations of the heating light source in the optical floating zone method, meeting the growth requirements for large-sized gallium oxide single crystals of 2 inches and above. This application embodiment allows adjustment of the size of the suspended heat source within the allowable heating power of the induction coil, thereby enabling the generation of gallium oxide single crystal rods of different sizes as needed, including large-sized gallium oxide single crystal rods.

[0084] Another embodiment of this application provides a method for growing gallium oxide single crystals, such as... Figure 2 The diagram shown is a flowchart of this growth method. Figure 3 The diagram shown is a cross-sectional view illustrating the operational state of the gallium oxide single crystal growth apparatus during the growth process. This growth method employs techniques described in the above embodiments. Figure 1 The gallium oxide single crystal growth apparatus shown is illustrated. Specifically, the growth method includes the following steps:

[0085] Step S11: Install the gallium oxide rod 21 onto the upper seed crystal rod 2, and install the gallium oxide seed crystal 31 onto the lower seed crystal rod 3. As described in the above embodiments, various methods such as threaded installation and snap-fit ​​can be used, as long as the gallium oxide rod 21 and the gallium oxide seed crystal 31 are stably installed.

[0086] Step S12: A first flowing gas is introduced into the furnace cylinder through the first gas channel and the second gas channel to form a stable flowing atmosphere within the furnace cylinder. Specifically, the air inlet channel of the lower cover and the air outlet channel of the upper cover inside the sealed furnace body are opened, and the first flowing gas is introduced from bottom to top to form a stable flowing atmosphere.

[0087] It should be noted that a stable flow atmosphere refers to a gas flow direction that is generally unidirectional. This can be understood as the gas inside the furnace being in a laminar flow state. In laminar flow, the movement of gas molecules along the flow direction exhibits a regular and parallel flow pattern. Specifically, the characteristics of laminar flow are: ordered flow: gas molecules flow along fixed paths without lateral mixing; parallel flow: all gas molecules flow in a direction parallel to the pipe axis. In the embodiments of this application, the preferred gas flow direction inside the furnace is along the central axis of the furnace, flowing from bottom to top; and no turbulence: there are no obvious vortices or irregular flow phenomena.

[0088] As described in the above embodiments, the first gas channel 14 is an outlet channel and the second gas channel 16 is an inlet channel. During operation, a bottom-up gas channel is formed, allowing the gas in the lower-temperature inlet channel to preferentially contact the grown gallium oxide single crystal. On the one hand, this can accelerate the growth rate of the gallium oxide single crystal. On the other hand, during the crystal growth process, the gallium oxide rod and the suspended heat source area require high temperatures. During the bottom-up gas flow, the gas temperature can be gradually increased, thereby reducing the impact of the gas temperature on the temperature of the gallium oxide rod and the suspended heat source area.

[0089] Step S13: Pass an alternating current of a preset frequency and preset magnitude into the induction coil to form a high-frequency alternating magnetic field of target frequency and target power in the working area enclosed by the induction coil in the furnace drum.

[0090] As described in the above embodiments, since the winding directions of the stabilizing coil 41, heating coil 42, and levitation coil 43 are opposite, a high-frequency alternating magnetic field can be formed in the working area enclosed by the induction coil simply by passing an alternating current through it. Figure 5 As shown, this is an example of the current direction in the stabilizing coil 41, the heating coil 42, and the levitation coil 43. After all parts of the induction coil are connected to the same AC power source, since the winding directions of the stabilizing coil 41, the heating coil 42, and the levitation coil 43 are opposite, the current directions in the stabilizing coil 41, the heating coil 42, and the levitation coil 43 are also opposite.

[0091] During operation, considering the size of the gallium oxide single crystal to be generated and the weight of the suspended heat source, in this embodiment, it is preferred that the frequency of the induction coil is within 1kHz-500kHz and the power of the induction coil is within 1kW-2000kW. Furthermore, the frequency of the induction coil remains unchanged during operation to maintain the stable suspension of the suspended heat source.

[0092] In other embodiments, in order to ensure that the induction coil can still operate normally without damage when the temperature rises due to high power energization, when an alternating current is applied to the induction coil, coolant (such as cooling water) can be continuously introduced into the hollow structure inside the metal pipe of the induction coil in a timely manner according to the temperature rise of the induction coil, so as to reduce the operating temperature of the induction coil.

[0093] Step S14: Enter the feeding stage: that is, the suspended heat source material is fed into the furnace cylinder 11 through the feeding channel 13.

[0094] Under the action of the high-frequency alternating magnetic field, the stabilizing coil 41 generates a downward first electromagnetic force after being energized, and the levitation heating coil generates an upward second electromagnetic force after being energized. The first electromagnetic force and the second electromagnetic force interact to melt the levitation heat source material in the working area to obtain the levitation heat source 5. The levitation heat source is stably suspended in the working area, and the levitation heat source material is a conductive material.

[0095] Specifically, when the levitation heating coil is divided into a heating coil 42 and a levitation coil 43 (from top to bottom), the heating coil 42 and the levitation coil 43 jointly provide an upward second electromagnetic force to overcome the gravity of the levitation heat source and levitate it. The stabilizing coil 41 provides a downward first electromagnetic force to maintain the stable levitation of the levitation heat source. Under the combined action of the second electromagnetic force, the first electromagnetic force, and the gravity of the levitation heat source, the levitation heat source remains stable and does not oscillate up and down. The heating coil 42 provides heat energy to the levitation heat source material to melt the levitation heat source material, thereby obtaining the levitation heat source 5.

[0096] The suspended heat source material has good electrical conductivity, enabling it to levitate under electromagnetic force. Furthermore, the boiling point of the suspended heat source material is higher than the melting point of the gallium oxide rod, ensuring that the surface temperature of the suspended heat source in the molten state can melt the gallium oxide rod. Additionally, the suspended heat source material exhibits low reactivity or a low solid solution limit with the molten gallium oxide rod, and does not alter the electrical properties of the gallium oxide single crystal in the molten state.

[0097] Furthermore, when the electrical type of the gallium oxide single crystal is n-type, the suspended heat source material is Sn, Si, Ta, or Nb; when the electrical type of the gallium oxide single crystal is semi-insulating, the suspended heat source material is Fe or Mg; when the electrical type of the gallium oxide single crystal is unintentionally doped, the suspended heat source material is Ga.

[0098] It should be noted that the operating temperature of the suspended heat source is T1, and the melting point of the gallium oxide rod is T2, where T1 > T2. The melting point T2 of the gallium oxide rod is between 1740℃ and 1900℃. Therefore, the operating temperature T1 of the suspended heat source is within the range of 1750℃-1900℃.

[0099] During operation, to ensure that the temperature inside the furnace drum is maintained at or above the melting point of the suspended heat source, the power of the induction coil is within the range of 1kW-2000kW. To maintain the suspended state of the suspended heat source, the frequency of the induction coil is within the range of 1kHz-500kHz, and the frequency of the induction coil remains constant during operation.

[0100] Step S15: Entering the feeding stage: The upper seed crystal rod 2 descends at a first rate V1, causing the bottom end of the gallium oxide rod 21 to approach and contact the suspended heat source 5, causing the gallium oxide rod 21 to be heated and melted. The upper seed crystal rod continues to descend until the molten gallium oxide rod material completely covers the suspended heat source 5, forming a suspended melt. The suspended melt remains suspended under the action of the high-frequency alternating magnetic field.

[0101] It should be noted that the core of this suspended melt is a molten suspended heat source 5, and the outer layer is molten gallium oxide rod material (i.e., suspended melt zone 22). Once the suspended melt is formed, the surface of the suspended heat source 5 is enveloped by the molten gallium oxide rod material. At this point, the suspended heat source 5 will no longer come into contact with the gas atmosphere inside the furnace. That is, even if oxygen-containing gas is introduced at this time, the suspended heat source 5 will not be oxidized. Furthermore, gallium oxide rods are typically non-conductive materials, and a single gallium oxide rod material will not suspend in an alternating magnetic field. Therefore, after the rod melts and envelops the suspended heat source, the good conductivity of the suspended heat source allows the suspended melt to remain suspended in the alternating magnetic field. Further, after the suspended melt is formed, its weight is greater than that of the suspended heat source 5. Therefore, to maintain the suspended state of the suspended melt, theoretically, the frequency or power of the induction coil needs to be adjusted to appropriately increase the upward second electromagnetic force.

[0102] As described in the above embodiments, this application does not limit the shape of the suspended heat source. The shape of the suspended heat source includes, but is not limited to, an inverted cone, a sphere, or a cylinder, as long as it can be stably suspended and can melt the gallium oxide rod material. Furthermore, this application does not limit the weight of the suspended heat source. As long as an appropriate weight of suspended heat source is selected according to the size of the gallium oxide single crystal to be grown, for growing gallium oxide single crystals with a diameter of 2 inches or more, in this embodiment, the weight m of the suspended heat source is preferably within 1g-100g.

[0103] In this embodiment, the diameter of the side of the suspended heat source 5 that contacts the gallium oxide rod is D1, the diameter of the gallium oxide rod is D2, and the diameter of the grown gallium oxide single crystal is D3. In order to facilitate faster melting of the gallium oxide rod, D1≥D2, and the diameter of the grown gallium oxide single crystal is D3≥D2.

[0104] In this embodiment, the suspended heat source is shaped like an inverted cone. The bottom diameter of the suspended heat source is D1, the weight is m, and the density is ρ, where D1 = (24m × tanβ / (πρ))^(1 / 3).

[0105] Step S16: Stop the introduction of the first flowing gas, start the introduction of the second flowing gas, and form a stable flowing atmosphere.

[0106] The function of the first flowing gas is to protect the suspended heat source from oxidation during the heating and melting process. Therefore, the first flowing gas is preferably an inert gas, and more preferably, argon or nitrogen.

[0107] The function of the first flowing gas is to facilitate the growth of gallium oxide single crystals and inhibit the decomposition and volatilization of the gallium oxide melt. The growth process of gallium oxide single crystals requires an oxygen-containing atmosphere; the higher the oxygen concentration, the smoother the growth process. Therefore, in this embodiment, the second flowing gas comprises a mixture of oxygen and other gases, including one or more of carbon dioxide, argon, and nitrogen. The oxygen content in the second flowing gas is X, where 0 < X ​​≤ 100%.

[0108] It should be noted that there are various doping methods for gallium oxide single crystals, including but not limited to solid-state doping and gas-phase doping during the growth process. Solid-state doping involves adding a dopant element to the raw material and then introducing the dopant element into the crystal during the crystal growth process. Gas-phase doping involves introducing the dopant element through a gas source during the crystal growth process.

[0109] If solid-state doping is used to grow gallium oxide single crystals, the doping of gallium oxide rod 21 and gallium oxide seed crystal 31 is matched with the electrical type of the gallium oxide single crystal to be grown. When the electrical type of the gallium oxide single crystal to be grown is n-type, the doping elements of gallium oxide rod 21 and gallium oxide seed crystal 31 can be donor impurities such as selenium (Se), tin (Sn), and indium (In); when the electrical type of the gallium oxide single crystal to be grown is p-type, the doping elements of gallium oxide rod 21 and gallium oxide seed crystal 31 can be acceptor impurities such as boron (B), magnesium (Mg), zinc (Zn), and aluminum (Al); when the electrical type of the gallium oxide single crystal to be grown is unintentional doping, gallium oxide rod 21 and gallium oxide seed crystal 31 are not doped with other elements.

[0110] If gallium oxide single crystals are grown using vapor phase doping, the second flowing gas contains dopant elements that match the electrical type of the gallium oxide single crystal to be grown. When the electrical type of the gallium oxide single crystal to be grown is n-type, the dopant elements in the second flowing gas can be donor impurities such as selenium (Se), tin (Sn), and indium (In); when the electrical type of the gallium oxide single crystal to be grown is p-type, the dopant elements in the second flowing gas can be acceptor impurities such as boron (B), magnesium (Mg), zinc (Zn), and aluminum (Al); when the electrical type of the gallium oxide single crystal to be grown is unintentionally doped, the second flowing gas does not contain any other elements.

[0111] Step S17: Entering the crystal growth stage: Raise the lower seed crystal rod 3 so that the top of the gallium oxide seed crystal 31 approaches and contacts the bottom of the suspended melt. When the top of the gallium oxide seed crystal 31 contacts the suspended melt zone 22 on the outer layer of the suspended melt, adjust the descent rate of the lower seed crystal rod so that the gallium oxide single crystal begins to grow along the top of the gallium oxide seed crystal until the grown gallium oxide single crystal reaches the target size. Continue to lower the lower seed crystal rod until the generated gallium oxide crystal separates from the suspended melt, and then the upper seed crystal rod stops descending.

[0112] During the growth of the gallium oxide single crystal, the upper seed crystal rod 2 continuously descends to continuously melt the gallium oxide rod and maintain the state of the suspended melt, while the second flowing gas is continuously introduced into the furnace cylinder 11.

[0113] like Figure 4 As shown, after entering the crystal growth stage, the molten gallium oxide rod material gradually forms a molten pool 23 under the suspended melt. The material at the bottom of the molten pool 23 is cooled under the guidance of the seed crystal to form a single crystal consistent with the seed crystal.

[0114] The crystal growth stage is based on the growth of gallium oxide single crystals of the target size. The specific growth process can be adjusted according to the shape and other requirements of the target gallium oxide single crystal. This embodiment does not limit this.

[0115] Step S18: Entering the shutdown stage: Maintain the suspended melt state and continue to suspend, stop the supply of the second flowing gas, start the supply of the first flowing gas, until the molten gallium oxide rod material (i.e., the suspended melt zone) encapsulating the suspended heat source in the suspended melt volatilizes and decomposes, stop the supply of the first flowing gas, start the supply of the second flowing gas, and gradually reduce the power of the induction coil to zero, so that the suspended heat source oxidizes and cools down to form a solid block and falls; when the furnace temperature drops to the target temperature, stop the supply of the second flowing gas.

[0116] Gallium oxide in its molten state exhibits characteristics of easy decomposition and volatility. Its volatilization requires the following conditions: maintaining a molten state and reducing the oxygen content in the atmosphere. Therefore, in this embodiment, utilizing the easy decomposition and volatility of gallium oxide in its molten state, the frequency and power of the induction coil are kept constant to ensure that the suspended molten zone on the outer layer of the suspended molten zone remains in a molten state. Furthermore, the flow of the second oxygen-containing gas is stopped and replaced with an inert gas. This facilitates the volatilization of the suspended molten zone in an oxygen-free atmosphere and protects the suspended heat source, preventing oxidation during the volatilization process and thus avoiding instability in the suspended state.

[0117] After the suspended molten zone evaporates and decomposes, taking advantage of the fact that the suspended heat source is easily oxidized and its conductivity decreases after oxidation, the inert gas is stopped and replaced with a second flow gas containing oxygen. This causes the suspended heat source to oxidize and cool down, forming a solid block that falls onto the gallium oxide single crystal or the lower cover. Then, the power of the induction coil is reduced to 0. When the temperature inside the furnace drops to room temperature, the gas supply is stopped, and the furnace is opened to remove the gallium oxide single crystal and the oxidized suspended heat source.

[0118] It should be noted that, in each stage of steps S12-S18, this application does not specifically limit the flow rate of the first or second flowing gas introduced in each stage. The gas flow rate can be adaptively adjusted according to the growth rate of the gallium oxide single crystal and the requirements of temperature, gas pressure, etc. in the furnace. Theoretically, the larger the size of the grown gallium oxide single crystal and the larger the diameter of the furnace, the higher the required gas flow rate. In order to maintain the stability of the gas flow during the crystal growth process, in a preferred embodiment of this application, the gas flow rate remains unchanged in each stage, and the gas flow rate is preferably within 0.1 L / min-100 L / min.

[0119] Furthermore, throughout steps S12-S18, since impurities are easily deposited at the gas outlet, in order to prevent the impurities in the gas outlet from being blown back into the furnace cylinder and causing contamination of the gallium oxide single crystal, it is necessary to keep the gas flow direction consistent throughout the entire process and not to easily change the gas flow direction.

[0120] In this embodiment, no precious metals such as iridium are involved in the entire growth process. Only a spiral induction coil wound around the periphery of the furnace cylinder provides a high-frequency alternating magnetic field when energized. The interaction between the downward first electromagnetic force generated by the energized stabilizing coil in the induction coil and the upward second electromagnetic force generated by the suspension heating coil allows the suspended heat source material, which is fed into the furnace cylinder through the feeding channel above the furnace cylinder, to be stably suspended in the working area enclosed by the induction coil during operation. Furthermore, the suspension heating coil can also heat the suspended heat source material, causing it to melt and obtain a suspended heat source. Throughout the crystal growth process, the suspended heat source is kept in a molten working state.

[0121] During crystal growth, a molten suspended heat source is used as the heat source to contact a gallium oxide rod mounted on the upper seed crystal rod. The gallium oxide rod is heated, melting and completely enveloping the suspended heat source, forming a suspended melt. This suspended melt has a molten core as its core and a molten gallium oxide rod as its outer layer. After obtaining the suspended melt, the upper seed crystal rod continues to descend, causing the rod to continue melting, while the lower seed crystal rod rises, bringing the gallium oxide seed crystal into contact with the suspended melt, thus initiating the crystal growth process until a gallium oxide single crystal of the target size is obtained, at which point the furnace is shut down. Since molten gallium oxide easily volatilizes in an oxygen-deficient atmosphere, this application first creates an oxygen-deficient atmosphere inside the furnace to allow the molten gallium oxide rod material on the outer layer of the suspended melt to volatilize. Furthermore, because the suspended heat source material can oxidize to form oxide solids in an oxidizing atmosphere, the poor conductivity of the oxides reduces the electromagnetic levitation force, allowing it to gradually descend to the bottom of the furnace for removal.

[0122] A flowchart of a gallium oxide single crystal growth method disclosed in another embodiment of this application is shown below. Figure 3 As shown, with Figure 2 The method shown differs in that it further clarifies the specific processes of the crystal growth stages. Specifically, the crystal growth stages include the crystal introduction stage, necking stage, shoulder formation stage, equal diameter stage, and finishing stage in steps S27-S31. The processes of steps S21-S26 and S32 in this embodiment are similar to those of steps S11-S16 and S18 in the previous embodiment, and will not be described again here. Specifically, the processes of each stage of the crystal growth in this embodiment are as follows:

[0123] Step S27: Crystal introduction stage: The lower seed crystal rod 3 rises at a second rate V2, so that the top of the gallium oxide seed crystal 31 approaches and contacts the bottom of the suspended melt, so that the top of the gallium oxide seed crystal 31 approaches and contacts the bottom of the suspended melt zone 22 on the outer layer of the suspended melt, so that the gallium oxide material in the molten state of the suspended melt zone gradually solidifies and grows into a gallium oxide single crystal consistent with the seed crystal under the crystal introduction effect of the seed crystal.

[0124] The seed crystal introduction process can be divided into a preheating process and a post-preheating process. The preheating process involves slowly raising the seed crystal rod 3 so that the top of the gallium oxide seed crystal 31 is close to but does not contact the bottom of the floating molten zone 22. The raising of the seed crystal rod 3 is stopped, and it remains at this position for a certain period of time so that the seed crystal can be preheated under the influence of the heat of the floating molten zone 22. After the preheating is completed, the seed crystal rod 3 is raised again so that the top of the gallium oxide seed crystal 31 contacts the bottom of the floating molten zone 22.

[0125] In this embodiment, the specific value of V2 is not limited and can be adjusted according to the actual situation, as long as the state of the gallium oxide seed crystal is controllable.

[0126] Step S28: Necking Stage: The lower seed crystal rod 3 descends at a third rate V3, causing the gallium oxide single crystal to begin growing along the top of the gallium oxide seed crystal 31 and forming a narrow neck. During this process, the upper seed crystal rod 2 continues to descend, so that the gallium oxide rod continues to melt and maintain the state of the suspended melt. Similarly, in this embodiment, the specific value of V3 is not limited and can be adjusted according to the actual situation to ensure that the state of the crystal growth process is controllable.

[0127] During this process, the seed crystal rod 3 descends, providing a certain growth time and cooling time for the gallium oxide single crystal growth. During this process, the power and frequency of the induction coil remain unchanged.

[0128] Step S29: Shoulder Formation Stage: The lower seed crystal rod 3 descends at a fourth rate V4, and / or the power of the induction coil 4 is reduced, causing the diameter of the grown gallium oxide single crystal to increase. During this process, the upper seed crystal rod continues to descend to melt the gallium oxide rod and maintain the state of the suspended melt, where V4 < V3. During crystal growth, the gallium oxide rod material, still in a molten state, gathers below the suspended melt to form a molten pool 23. The diameter of the molten pool 23 directly affects the diameter of the gallium oxide single crystal.

[0129] During the crystal growth stage, reducing the descent speed of the lower seed rod 3, while keeping the melting rate of the gallium oxide rod essentially constant, increases the diameter and volume of the molten pool 23, thereby increasing the diameter of the gallium oxide single crystal. Furthermore, reducing the power of the induction coil 4 lowers the temperature inside the furnace, especially in the suspended melt region and the molten pool region in contact with the suspended melt. With the descent speed of the lower seed rod 3 unchanged, the lower temperature inside the furnace accelerates crystallization, leading to a larger and longer diameter of the gallium oxide single crystal.

[0130] In this embodiment, the descent speed of the seed crystal rod 3 can be reduced separately, or the power of the induction coil 4 can be reduced separately. Alternatively, the descent speed of the seed crystal rod 3 can be reduced at the same time, or the power of the induction coil 4 can be reduced. This embodiment does not limit this.

[0131] Step S30: Equal diameter stage: After the diameter of the grown gallium oxide single crystal expands to the target size, the lower seed crystal rod 3 descends at a fifth rate V5 to maintain the diameter of the grown gallium oxide single crystal at the target size. During this process, the upper seed crystal rod continues to descend to melt the gallium oxide rod and maintain the state of the suspended melt, where V5 < V4.

[0132] During the constant diameter stage, once the diameter of the gallium oxide single crystal has reached the target size, maintaining a stable descent rate of the lower seed rod 3, or maintaining the power of the induction coil, will keep the diameter of the molten pool 23 at the target size, thus maintaining the diameter of the grown gallium oxide single crystal at the target size. In this embodiment, during the constant diameter stage, the descent rate of the lower seed rod (i.e., the growth rate of the gallium oxide single crystal) V5 is preferably within 0.5 mm / h to 50 mm / h.

[0133] Step S31: Finishing stage: When the length of the grown gallium oxide single crystal reaches the target size, the lower seed crystal rod 3 descends at a sixth rate V6, and / or the power of the induction coil is increased, so that the diameter of the grown gallium oxide single crystal gradually shrinks until it separates from the suspended melt. When the gallium oxide single crystal separates from the suspended melt, the upper seed crystal rod stops descending, where V6 > V5.

[0134] It should be noted that, compared to the constant diameter stage, in the final stage, increasing the descent speed of the lower seed rod 3, while keeping the melting rate of the gallium oxide rod essentially constant, can reduce the diameter and volume of the molten pool 23, thereby reducing the diameter of the gallium oxide single crystal. Besides increasing the descent speed of the lower seed rod 3, the power of the induction coil 4 can also be increased. Increasing the power of the induction coil 4 will raise the temperature inside the furnace, especially in the suspended melt region and the molten pool region in contact with the suspended melt. With the descent speed of the lower seed rod 3 remaining constant, the increased temperature inside the furnace will inhibit crystallization, reduce the crystallization rate, and thus reduce the diameter of the gallium oxide single crystal.

[0135] Of course, in this process, the descending speed of the lower seed crystal rod 3 or the power of the induction coil 4 can be increased separately, or the descending speed of the lower seed crystal rod 3 and the power of the induction coil 4 can be increased simultaneously. This embodiment does not limit this, as long as the diameter of the gallium oxide single crystal can be reduced.

[0136] In this embodiment, the entire crystal growth stage is similar to the previous embodiment, where the flow rate of the first flowing gas is equal to the flow rate of the second flowing gas. Furthermore, throughout the crystal growth process, the volume of the suspended melt can increase or remain constant, as long as it can maintain stable suspension within the furnace tube and the suspended melt zone 22 can completely enclose the suspended heat source, preventing the suspended heat source from contacting the oxygen-containing second flowing gas.

[0137] It should be noted that during the entire crystal growth stage, the size and speed of crystal growth can be controlled by controlling the rising or falling rate of the upper seed crystal rod 2 and the lower seed crystal rod 3. Alternatively, the size and speed of crystal growth can be controlled by controlling the power of the induction coil. The speed of the upper seed crystal rod 2 and the lower seed crystal rod 3 and the power of the induction coil can also be flexibly adjusted simultaneously, as long as the growth requirements of the single crystal are met. This embodiment does not limit the specific speed or power adjustment method.

[0138] Using the method disclosed in the embodiments of this application, gallium oxide single crystals with a diameter of 2 inches to 8 inches can be grown. It is understood that, theoretically, larger gallium oxide single crystals can be grown using the method disclosed in the embodiments of this application. The larger the size of the grown gallium oxide single crystal, the larger the size of the levitation heat source required, which necessitates greater heating power and levitation force, i.e., providing greater power to the induction coil. However, the power that the induction coil can withstand has a limit; exceeding this limit will lead to the destruction of the induction coil. Therefore, the size of the grown gallium oxide single crystal is also limited. Of course, by adjusting the material of the induction coil or the cooling efficiency of the coolant, the size of the gallium oxide single crystal can be appropriately increased.

[0139] The following example illustrates the gallium oxide single crystal growth method disclosed in this application, using the growth of a 2-inch unintentionally doped gallium oxide single crystal as an example.

[0140] Step 1: Assemble the gallium oxide single crystal growth device. Install the gallium oxide rod on the upper seed crystal rod and the gallium oxide seed crystal on the lower seed crystal rod. Then close the upper and lower covers to form a sealed space inside the furnace.

[0141] The furnace cylinder can be a quartz cylinder. A suspended heat source material is prepared; in this embodiment, the suspended heat source material is preferably metallic Ga, weighing 5g. The number of turns in the stabilizing coil is N1≤10, the number of turns in the heating coil is N2≤20, and the number of turns in the suspended coil is N3≤20. Taking a 7-turn induction coil as an example, N1=1, N2=4, N3=2, and the vertical spacing between the turns is d1=d2=d3=1mm. The diameters of the stabilizing and heating coils can be 80mm-100mm, preferably 90mm. The diameter of the suspended coil can be equal to that of the heating coil, or it can be an inverted cone. If it is an inverted cone, the semi-cone angle of the suspended coil is 10°<β≤30°, preferably β=18.5°. The diameter of the suspended coil can be between 80mm-90mm. If the outer diameter of the quartz cylinder is 80mm, the minimum diameter of the suspended coil can be 82mm, allowing space for the thermal expansion of the quartz cylinder and gas flow.

[0142] Step 2: Open the lower cover air inlet channel and the upper cover air outlet channel of the sealed furnace cylinder, and introduce the first flowing gas from top to bottom to form a stable flowing atmosphere. The first flowing gas is preferably argon.

[0143] Step 3, the feeding stage, also known as the suspension heat source preheating stage, involves setting the frequency of the induction coil to 100kHz and rapidly increasing the power to 20kW. Then, the suspension heat source material is fed into the furnace cylinder inside the induction coil through the feeding channel. This allows the suspension heat source material to melt and form an inverted cone shape, which is then stably suspended. The area enclosed by the induction coil is then heated to the melting point of the gallium oxide rod, such as 1800℃.

[0144] Step 4, Feeding Stage. The upper seed crystal rod descends, causing the bottom of the rod to gradually approach the suspended heat source. The rod melts under the heat, and the molten material surrounds the suspended heat source. The feeding continues slowly, increasing the volume of the suspended molten zone until the suspended heat source is completely surrounded, resulting in a suspended melt.

[0145] Step 5: Stop introducing argon gas into the furnace cylinder and instead introduce a second flowing gas to form a stable flowing atmosphere. The second flowing gas can be a mixture of 20% oxygen and 80% carbon dioxide.

[0146] Step 6, Seed Crystal Development Stage. The seed crystal rod is raised so that the top of the seed crystal is close to the bottom of the suspended heat source for preheating; after preheating for about 20 minutes, the seed crystal rod continues to rise slowly so that the top of the seed crystal contacts the bottom of the suspended melt.

[0147] Step 7, Necking Stage. The lower seed crystal rod then descends at a speed of 20 mm / h, causing the crystal to begin growing along the tip of the seed crystal and forming a narrow neck. During this process, the upper seed crystal rod continuously descends, melting the material rod to maintain a constant volume of the suspended melt.

[0148] Step 8, Shoulder Formation Stage. Reduce the descent rate of the lower seed crystal rod to 5 mm / h to increase the diameter of the gallium oxide single crystal. During this process, the upper seed crystal rod continuously descends to melt the material rod, maintaining a constant volume of the suspended melt.

[0149] Step 9, Constant Diameter Stage. Once the crystal diameter reaches 2 inches, increase the descent rate of the lower seed crystal rod to 10 mm / h to maintain a constant diameter while gradually increasing the length of the gallium oxide single crystal. During this process, the upper seed crystal rod continuously descends, melting the material rod to maintain a constant volume of the suspended melt.

[0150] Step 10, Final Stage. Increase the descent rate of the lower seed crystal rod to 20 mm / h, gradually reducing the diameter of the gallium oxide single crystal until it separates from the melt. Once the crystal has separated from the melt, the upper seed crystal rod stops descending.

[0151] Step 11, Furnace Shutdown Stage. Maintaining the frequency and power of the induction coil, the suspended melt continues to float. Argon gas is introduced to allow the molten gallium oxide material in the suspended zone to completely volatilize and decompose, exposing the suspended heat source. A second flow of gas is then introduced, causing the suspended heat source to gradually oxidize and form an oxide solid, which then cools and solidifies, eventually settling onto the gallium oxide crystal or its lower cover. The induction coil power is then slowly reduced to zero. Once the furnace temperature drops to room temperature, the gas supply is stopped, and the furnace is opened to remove the grown gallium oxide single crystal.

[0152] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0153] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0154] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0155] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0156] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0157] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0158] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0159] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0160] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A crucible-free gallium oxide single crystal growth apparatus, characterized by comprising: The application relates to a gallium oxide single crystal growth device and a gallium oxide single crystal growth method. The device comprises a furnace body, an upper seed crystal rod penetrating through the upper cover, a lower seed crystal rod penetrating through the lower cover, a spiral induction coil surrounding the periphery of the furnace cylinder, and a gallium oxide seed crystal. The furnace body comprises a furnace cylinder, an upper cover and a lower cover arranged at the two ends of the furnace cylinder respectively, a feeding channel and a first gas channel are arranged on the upper cover and communicate with the inside of the furnace cylinder, the feeding channel is used for feeding a suspended heat source material into the furnace cylinder, a second gas channel is arranged on the lower cover and communicates with the inside of the furnace cylinder; the first gas channel is an outlet gas channel, the second gas channel is an inlet gas channel; the suspended heat source material is a conductive material; The upper seed crystal rod is used for arranging a gallium oxide material rod; The lower seed crystal rod is used for arranging a gallium oxide seed crystal; The spiral induction coil is used for providing a high-frequency alternating magnetic field; the induction coil comprises a stabilizing coil and a suspended heating coil from top to bottom; the stabilizing coil generates a downward first electromagnetic force after being electrified; the suspended heating coil generates an upward second electromagnetic force after being electrized; the first electromagnetic force and the second electromagnetic force interact to make the suspended heat source fed into the furnace cylinder stably suspend in a working area surrounded by the induction coil in a working state; The suspended heating coil comprises a heating coil and a suspended coil from top to bottom; the heating coil is cylindrically wound; the suspended coil is inversely conically wound; the half-cone angle beta of the suspended coil is arranged in the range of 0 < beta <= 90 degrees; the winding vertical interval of the heating coil is d2; the winding vertical interval of the suspended coil is d3; d2 >= d3; the suspended heat source material is heated to be molten to obtain the suspended heat source; the shape of the suspended heat source is controlled to be inversely conical; and the suspended heat source is kept in a molten working state during the whole crystal growth process; The working temperature of the suspended heat source is T1; the melting point of the gallium oxide material rod is T2; T1 > T2; the suspended heat source material has good conductive performance and a boiling point higher than the melting point of the gallium oxide material rod; the reaction activity of the suspended heat source material with the gallium oxide material rod in a molten state is low or the solid solution limit is low; and the suspended heat source material does not change the electrical type of the gallium oxide single crystal in a molten state; The suspended heat source in a molten state has an inversely conical shape and is used as a heat source in the crystal growth process; the suspended heat source contacts the gallium oxide material rod arranged on the upper seed crystal rod, heats the gallium oxide material rod, and makes the gallium oxide material rod melt and completely wrap the suspended heat source to form a suspended melt and guide the flow path of the molten gallium oxide material rod; the suspended melt keeps suspending under the action of the high-frequency alternating magnetic field, contacts the gallium oxide seed crystal, starts the crystal growth process, and obtains the gallium oxide single crystal with a target size; 2. The gallium oxide single crystal growth apparatus without a crucible according to claim 1, characterized by The weight of the suspended heat source is related to the diameter size of the gallium oxide single crystal to be generated; the number of turns N3 and the winding vertical interval d3 of the suspended coil are strongly related to the weight of the suspended heat source; the number of turns N2 and the winding vertical interval d2 of the heating coil are also strongly related to the weight of the suspended heat source. The winding direction of the stabilizing coil is opposite to the winding direction of the suspended heating coil. And / or, the metal pipe inside which the induction coil is wound is hollow structure, the metal pipe in which the stabilizing coil is wound and the metal pipe in which the levitation heating coil is wound are communicated with each other.

3. The gallium oxide single crystal growth apparatus without crucible according to claim 1, characterized by The number of turns of the stabilizing coil is N1, wherein N1≤N2 and N1≤N3. And / or, the vertical spacing of turns of the stabilizing coil is d1, wherein d1≥d2 and d1≥d3.

4. The gallium oxide single crystal growth apparatus without crucible according to any one of claims 1 to 3, characterized by, The furnace cylinder is sapphire cylinder or quartz cylinder. And / or, the diameter of the gallium oxide single crystal grown by using the gallium oxide single crystal growth device is D, and the inner diameter of the furnace cylinder is within the range of 1.2D-3D.

5. A method for growing a gallium oxide single crystal, characterized by, The gallium oxide single crystal growth device is used for growing gallium oxide single crystal, and the growth method comprises the following steps: A gallium oxide rod is installed on the upper seed rod, and a gallium oxide seed crystal is installed on the lower seed rod. The gas inlet channel of the lower cover and the gas outlet channel of the upper cover in the closed furnace body are opened, the first flowing gas is introduced into the furnace cylinder from bottom to top through the first gas channel and the second gas channel, and a stable flowing atmosphere is formed in the furnace cylinder. An alternating current of a preset frequency and a preset size is introduced into the induction coil, so as to form a high-frequency alternating magnetic field of a target frequency and a target power in the working area surrounded by the induction coil in the furnace cylinder. The suspension heat source material is put into the furnace cylinder through the feeding channel, under the action of the high-frequency alternating magnetic field, the first electromagnetic force downward is generated after the stabilizing coil is electrified, the second electromagnetic force upward is generated after the levitation heating coil is electrified, the first electromagnetic force and the second electromagnetic force interact with each other, the suspension heat source material is melted in the working area, the suspension heat source in the shape of inverted cone is obtained, the suspension heat source is kept in the working state of melting during the whole crystal growth process, and the suspension heat source is stably suspended in the working area, wherein the working temperature of the suspension heat source is T1, the melting point of the gallium oxide rod is T2, T1>T2, the suspension heat source material has good electrical conductivity and high boiling point, the reaction activity of the suspension heat source material with the gallium oxide rod material in the molten state is low or the solid solution limit is low, and the electrical type of the gallium oxide single crystal is not changed in the molten state. The feeding stage is entered: the upper seed rod is lowered at a first speed V1, the bottom end of the gallium oxide rod is close to and contacts the suspension heat source, the gallium oxide rod is melted by heat, the upper seed rod is continuously lowered until the molten gallium oxide rod material completely wraps the suspension heat source, forms a suspension melt, and guides the flow path of the molten gallium oxide rod material; the suspension melt is kept suspended under the action of the high-frequency alternating magnetic field. The introduction of the first flowing gas is stopped, the second flowing gas is introduced, and a stable flowing atmosphere is formed. The gallium oxide single crystal is grown by using the gallium oxide single crystal growth device. Into the crystal growth stage: the lower seed rod is raised to make the top of the gallium oxide seed crystal close to and contact the lower part of the floating melt, the lowering rate of the lower seed rod is adjusted, the gallium oxide single crystal starts to grow along the top of the gallium oxide seed crystal, until the gallium oxide single crystal reaches the target size, the lower seed rod continues to be lowered, the generated gallium oxide crystal is separated from the floating melt, and then the upper seed rod stops descending; during the growth of the gallium oxide single crystal, the upper seed rod continues to descend to continuously melt the gallium oxide rod and maintain the state of the floating melt, and the second flowing gas continues to be introduced into the furnace cylinder; Into the shutdown stage: the state of the floating melt is maintained and continues to float, the introduction of the second flowing gas is stopped, the introduction of the first flowing gas is started, until the volatilization and decomposition of the molten gallium oxide rod material wrapping the floating heat source in the floating melt is completed, the introduction of the first flowing gas is stopped, the introduction of the second flowing gas is started, and the power of the induction coil is gradually reduced to zero, so that the floating heat source is oxidized and cooled to form a solid block and falls; when the temperature of the furnace cylinder decreases to the target temperature, the introduction of the second flowing gas is stopped.

6. The gallium oxide single crystal growth method according to claim 5, characterized by, The crystal growth stage includes a seeding stage, a necking stage, a shoulder stage, an equal-diameter stage, and an end stage, and the processes of each stage are as follows: Seeding stage: the lower seed rod is raised at a second rate V2 to make the top of the gallium oxide seed crystal close to and contact the lower part of the floating melt; Necking stage: the lower seed rod is lowered at a third rate V3 to make the gallium oxide single crystal start to grow along the top of the gallium oxide seed crystal and form a thin neck, during which the upper seed rod continues to descend to melt the gallium oxide rod and maintain the state of the floating melt; Shoulder stage: the lower seed rod is lowered at a fourth rate V4 and / or the power of the induction coil is reduced to make the diameter of the grown gallium oxide single crystal expand, during which the upper seed rod continues to descend to melt the gallium oxide rod and maintain the state of the floating melt, wherein V4 < V3; Equal-diameter stage: when the diameter of the grown gallium oxide single crystal expands to the target size, the lower seed rod is lowered at a fifth rate V5 to maintain the diameter of the grown gallium oxide single crystal at the target size, during which the upper seed rod continues to descend to melt the gallium oxide rod and maintain the state of the floating melt, wherein V5 < V4; End stage: when the length of the grown gallium oxide single crystal reaches the target size, the lower seed rod is lowered at a sixth rate V6 and / or the power of the induction coil is increased to gradually reduce the diameter of the grown gallium oxide single crystal until it is separated from the floating melt, and then the upper seed rod stops descending, wherein V6 > V5.

7. The gallium oxide single crystal growth method according to claim 5, characterized by, The first flowing gas is an inert gas, and the second flowing gas is a mixed gas containing oxygen and other gases, the other gases including one or more of carbon dioxide, argon, and nitrogen, and the oxygen content in the second flowing gas accounts for X, 0X≤100%; And / or, the flow rate of the first flowing gas is equal to the flow rate of the second flowing gas.

8. The gallium oxide single crystal growth method according to claim 5, characterized by, When the electrical type of the gallium oxide single crystal is n-type, the suspended heat source material is Sn, Si, Ta, or Nb; when the electrical type of the gallium oxide single crystal is semi-insulating type, the suspended heat source material is Fe or Mg; and when the electrical type of the gallium oxide single crystal is unintentionally doped, the suspended heat source material is Ga. And / or, the working temperature T1 of the suspended heat source is within the range of 1750-1900℃. And / or, the weight m of the suspended heat source is within the range of 1-100g.

9. The gallium oxide single crystal growth method according to claim 5, wherein The diameter of the surface of the suspended heat source in contact with the gallium oxide rod is D1, the diameter of the gallium oxide rod is D2, and the diameter of the gallium oxide single crystal is D3, wherein D1≥D2, and D3≥D2. And / or, when the shape of the suspended heat source is inverted conical, the bottom surface diameter of the suspended heat source is D1, the weight is m, and the density is p, wherein D1= (24m×tanβ / (πp))^(1 / 3). And / or, the diameter of the gallium oxide single crystal is within the range of 2-8 inches.

10. The gallium oxide single crystal growth method according to claim 6, characterized by, During the working process, the frequency of the induction coil is within the range of 1-500 kHz, the power of the induction coil is within the range of 1-2000 kW, and the frequency of the induction coil remains unchanged during the working process. And / or, in the constant diameter stage, the descending rate V5 of the lower seed crystal rod is within the range of 0.5-50 mm / h.

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