Oxide single crystal production device, gallium oxide single crystal production method, and gallium oxide single crystal

Abstract

The present invention relates to an apparatus for preparing an oxide single crystal, a method for preparing a gallium oxide single crystal using the same, and a gallium oxide single crystal prepared according to the method, and more particularly, to an apparatus for preparing a single crystal and a method for preparing a gallium oxide single crystal using the same, according to the present invention, a method in which oxide particles for producing a single crystal are used as a melting furnace instead of oxide particles per se for producing a single crystal is used as the melting furnace, thereby minimizing the problem of impurity inflow through the melting furnace, and the growth atmosphere of the oxide single crystal is maintained at a high oxygen atmosphere by using a method in which a hydrocarbon fuel gas and oxygen are mixed and heat is released by spark. Therefore, the high-quality oxide single crystal can be prepared.

Description

Technical Field

[0001] This invention relates to an apparatus for preparing oxide single crystals, a method for preparing gallium oxide single crystals, and gallium oxide single crystals. Background Technology

[0002] Since Y. Tomm et al. reported the growth of gallium oxide single crystals (especially β-Ga2O3 single crystals, hereinafter referred to as β-Ga2O3 single crystals) through the FZ and CZ methods in 2000, gallium oxide single crystals (especially β-Ga2O3 single crystals, hereinafter referred to as β-Ga2O3 single crystals) have been used as substrates for GaN thin film preparation in LEDs for research and development.

[0003] According to a recent report, M. Higashiwaki et al. have realized a FET for power devices using β-Ga2O3 single crystals. The preparation of high-quality, large-scale, and inexpensive β-Ga2O3 single crystals for wide-bandgap semiconductor substrates for power devices has attracted much attention.

[0004] β-Ga₂O₃ single crystals for device applications can be grown using methods such as the floating zone (FZ) method, the Czochralski (CZ) method, edge-defined film-fed growth (EFG) method, the vertical Bridgman (VB) method, and the HB method. Among these crystal growth methods, the FZ method, from its crystal growth principle perspective, does not require a container to maintain the molten raw material, and the method of heating the molten raw material to a high temperature (melting point) is relatively easy to implement. Therefore, there has been much research on this method to date. However, considering the growth principle and temperature environment, the FZ method has technical limitations in terms of large-scale, high-quality crystallization that suppresses structural defects such as dislocation. Despite much research over the past decade, it can still be said to be insufficient for device applications.

[0005] On the other hand, the CZ and EFG methods, which have long been industrially applicable for preparing large and high-quality single crystals, have been used in the growth of many single crystals. It is speculated that research and development of the CZ and EFG methods for β-Ga₂O₃ single crystal growth has been increasingly vigorous since 2000. However, to date, no large, high-quality, and inexpensive β-Ga₂O₃ single crystals capable of meeting the needs of future power device applications have been provided.

[0006] Currently, in order to solve the above problems, the VB method has recently attracted much attention, and there is active research on how to use it to prepare large, high-quality, and inexpensive β-Ga2O3 single crystals.

[0007] When crystal growth is performed using the CZ and EFG methods, a furnace is required to maintain the molten metal. Since β-Ga2O3 has a high melting point of approximately 1800°C, from a melting point perspective, suitable furnace materials could be high-melting-point metals such as Ir, Mo, and W.

[0008] However, when β-Ga₂O₃ is melted in a furnace at temperatures exceeding 1800°C, Mo or W, as furnace materials, have high reducing power and compete with β-Ga₂O₃ for oxygen to decompose, thus being oxidized themselves. Therefore, they are completely unsuitable for use as furnace materials. As a result, it is believed that Ir is the only high-melting-point metal suitable for CZ furnaces, EFG furnaces, and die materials.

[0009] However, through various experiments and theoretical investigations, it has become clear that Ir, which is currently used as a material for CZ process furnaces and EFG process furnaces (including mold materials), also has significant problems.

[0010] That is, Ir oxidation occurs in a high-temperature furnace exceeding 1800°C under oxygen partial pressures exceeding several percent, thus making it difficult to use as a stable furnace material. On the other hand, it has been determined that β-Ga2O3 undergoes an oxygen-loss decomposition reaction at high temperatures exceeding 1800°C under oxygen partial pressures below 10%, making it difficult to exist as a stable β-Ga2O3 solution.

[0011] As stated above, the oxygen partial pressure conditions required in the high-temperature furnace for β-Ga2O3 as the raw material molten liquid are clearly opposite to those required in the Ir furnace for holding gas. That is, Ir is also considered an unsuitable furnace material for containing β-Ga2O3 raw material molten liquid.

[0012] To elaborate further, while the CZ and EFG methods using existing Ir furnaces can grow β-Ga₂O₃ crystals under small-scale oxygen partial pressures (a few percent) within the furnace, experiments have revealed that the grown β-Ga₂O₃ crystals exhibit high-density oxygen defects due to insufficient oxygen, or problems such as evaporation, reduction, and degradation caused by Ir oxidation. Furthermore, oxygen defects act as n-type impurities, generating high donor concentrations, thus posing significant challenges to the realization of p-type β-Ga₂O₃ and other semiconductor device implementation problems.

[0013] To address the aforementioned problems, a method for growing β-Ga₂O₃ crystals in an atmospheric atmosphere using a Pt-Rh alloy furnace via the VB method was proposed. Since the β-Ga₂O₃ crystals are grown in the atmosphere, their decomposition is suppressed, and the Pt-Rh furnace solves the problem of furnace oxidation at high temperatures. However, experiments revealed that when molten β-Ga₂O₃ is placed in a Pt-Rh furnace at high temperatures and exposed for extended periods, a large amount of Rh was detected in the impurities of the grown β-Ga₂O₃ crystals.

[0014] Although the CZ, EFG, and VB methods are all advantageous for large-scale fabrication, they still detect a large amount of undesirable Si impurities. If β-Ga2O3 crystals containing a large amount of Si impurities are used to fabricate devices, problems will arise when using them as substrates due to insufficient insulation. Furthermore, β-Ga2O3 crystals grown by the CZ and EFG methods contain a large amount of Ga impurities generated by the decomposition of β-Ga2O3 in a low-oxygen atmosphere.

[0015] Existing technical documents

[0016] Patent documents

[0017] Patent Document 1: Japanese Patent Application Publication No. 2013-237591

[0018] Non-patent literature

[0019] Non-patent literature 1: N. Ueda, H. Hosono, R. Waseda, H. Kawazoe, Appl. Phys. Lett. 70 (1997) 3561. Summary of the Invention

[0020] The present invention is proposed to solve the above-mentioned problems. The purpose of the present invention is to provide a single crystal preparation apparatus for preparing high-quality oxide crystals and a method for preparing gallium oxide single crystals using the apparatus: by using flame-fusion, without using a furnace to hold molten gallium oxide, unwanted impurities are prevented from entering, and ultra-wide bandgap semiconductor gallium oxide crystals are prepared, which are used for materials and devices in extreme environments and are also required for the preparation of power devices.

[0021] The technical problem to be solved by this invention is not limited to the technical problem mentioned above. Those skilled in the art to which this invention pertains can clearly understand other technical problems not mentioned through the following description.

[0022] To achieve the above objectives, the present invention provides an oxide single crystal preparation apparatus, characterized in that it comprises: a heat source 100 for melting oxide particles; a growth section 200, made of refractory material, which is a space for loading the oxide particles and growing the oxide single crystal; a drive section 300 for moving the entire growth section to grow the oxide single crystal; and a measuring section 400 for measuring the temperature of the growth section throughout the entire process of oxide single crystal growth.

[0023] The heat source section 100 is characterized by comprising: a fuel gas supply section 101, wherein the fuel gas is composed of hydrocarbons; an oxygen supply section 102; a fuel pressure regulator 103 for regulating the pressure of fuel injected into the fuel pipe; an oxygen pressure regulator 104 for regulating the pressure of oxygen; a premixing zone section 107, which is a space for mixing the fuel gas and the oxygen; a fuel pipe 109 for allowing the fuel gas to flow into the premixing zone section 107; an oxygen pipe 110 for allowing the oxygen to flow in; a fuel flow regulator 105 for regulating the amount of fuel gas flowing into the premixing zone section 107; an oxygen flow regulator 106 for regulating the amount of oxygen; a nozzle 108 for releasing the mixture of fuel gas and oxygen mixed in the premixing zone section 107 to the outside; and a height regulator 111 for regulating the distance between the growth section 200 and the nozzle 108.

[0024] The growth section 200 is characterized in that it includes a refractory and heat-insulating material 201, which is used to create an atmosphere independent of the heat generated by the heat source section 100 and the oxygen atmosphere of the surrounding air, and has heat resistance.

[0025] The drive unit 300 is characterized by comprising: a support 304 for supporting the growth unit 200; a conveyor belt 301 for linearly moving the entire support 304; a motor 302 for driving the conveyor belt 301; a microcontroller 303 for controlling the driving of the motor 302; and a computer C for controlling the microcontroller 303.

[0026] The measuring unit 400 is characterized by including: an infrared camera 401 for measuring the temperature of the growth unit 200; and a computer C for receiving temperature data measured by the infrared camera.

[0027] Furthermore, the present invention provides a method for preparing gallium oxide single crystals, comprising: a sample preparation step S1, which prepares gallium oxide particles by processing gallium oxide powder; a growth preparation step S2, which creates a growth atmosphere and preheats the gallium oxide powder particles by loading them into an oxide single crystal preparation device; and a single crystal growth step S3, which grows the single crystal by driving a motor, thereby preparing gallium oxide single crystals.

[0028] The sample preparation step S1 is characterized by comprising: a calcination step S110, removing organic impurities and moisture from the gallium oxide powder and converting the gallium oxide powder into β-phase gallium oxide powder; a mixing step S120, mixing the calcined gallium oxide powder; a cold pressing step S130, compressing the mixed gallium oxide powder into a compressed powder; and a sintering step S140, heat-treating the cold-pressed gallium oxide powder to form particles.

[0029] The growth preparation step S2 is characterized by comprising: a loading step S210, loading the gallium oxide particles prepared in the sample preparation step S1 into an oxide single crystal preparation apparatus; a pressure adjustment step S220, adjusting the pressure of the fuel gas and oxygen used for initial spark ignition; a flow rate adjustment step S230, adjusting the flow rate of the fuel gas and oxygen; an ignition step S240, generating a spark; a preheating step S250, preheating the growth section and the gallium oxide particles after raising the temperature to a temperature above the melting point of the gallium oxide particles; a ratio adjustment step S260, adjusting the ratio of the fuel gas to oxygen to create an oxygen atmosphere in the melting region of the gallium oxide particles; and a melting step S270, heating the sample to a temperature above the melting point of the gallium oxide particles.

[0030] The oxide single crystal growth step S3 is characterized by comprising: a growth start step S310, in which a linear motor is driven to start the growth of a gallium oxide single crystal while the gallium oxide melt is prepared at a temperature above the melting point of the growth preparation step S2; a temperature holding step S320, in which the flow rate and pressure of the fuel gas and oxygen are adjusted to maintain the temperature of the growth section; an oxygen atmosphere holding step S330, in which the flow rate and pressure are adjusted to maintain the oxygen atmosphere of the growth section; a growth step S340, in which the gallium oxide single crystal is grown; a cooling step S350, in which the grown gallium oxide single crystal is cooled; and a single crystal extraction step S360, in which the gallium oxide single crystal grown on the gallium oxide particle is extracted.

[0031] Furthermore, the present invention provides a gallium oxide single crystal, characterized in that it is prepared according to the above-described preparation method.

[0032] The present invention employs a method that does not use an additional furnace, but instead uses the oxide particles used to prepare single crystals as the furnace itself, thereby minimizing the problem of impurities flowing into the furnace.

[0033] Furthermore, by using a method of releasing heat through a spark by mixing hydrocarbon fuel gas and oxygen, the growth atmosphere of oxide single crystals can be kept high-oxygen by adjusting the partial pressure of oxygen, thereby producing high-quality oxide single crystals with fewer defects.

[0034] Furthermore, the single crystal prepared by the preparation apparatus of the present invention prevents the introduction of unwanted impurities during the growth process to prepare a high-quality crystal, which is expected to be used both for the preparation of materials and devices for extreme environments and for the preparation of ultra-wide bandgap semiconductor materials required for power device fabrication.

[0035] The effects of this invention are not limited to those described above. Those skilled in the art to which this invention pertains can clearly understand other effects not mentioned from the description of the scope of protection of the invention. Attached Figure Description

[0036] Figure 1 An apparatus for preparing oxide single crystals according to an embodiment of the present invention is shown.

[0037] Figure 2 The heat source section 100 of an oxide single crystal preparation apparatus according to an embodiment of the present invention is shown.

[0038] Figure 3 The growth section 200 of an oxide single crystal preparation apparatus according to an embodiment of the present invention is shown.

[0039] Figure 4 The drive section 300 of an oxide single crystal preparation apparatus according to an embodiment of the present invention is shown.

[0040] Figure 5 The measuring section 400 of an oxide single crystal preparation apparatus according to an embodiment of the present invention is shown.

[0041] Figure 6 This is a process block diagram illustrating a method for preparing gallium oxide single crystals according to an embodiment of the present invention.

[0042] Figure 7 This is a process flowchart illustrating steps S1 to S3 of a gallium oxide single crystal preparation method according to an embodiment of the present invention.

[0043] Figure 8 The diagram illustrates the detailed steps of step S1 in a gallium oxide single crystal preparation method according to an embodiment of the present invention.

[0044] Figure 9 The temperature curve of the electric furnace in the calcination step S110 of the gallium oxide single crystal preparation method according to an embodiment of the present invention is shown.

[0045] Figure 10 A photograph of oxide particles prepared by the cold pressing step S130 of a gallium oxide single crystal preparation method according to an embodiment of the present invention is shown.

[0046] Figure 11 The temperature curve of the electric furnace in the sintering step S140 of the gallium oxide single crystal preparation method according to an embodiment of the present invention is shown.

[0047] Figure 12An algorithm is shown for growing a single crystal in the oxide single crystal growth step S3 of the gallium oxide single crystal preparation method according to an embodiment of the present invention.

[0048] Figure 13 The temperature curves in oxide single crystal growth step S3 of the gallium oxide single crystal preparation method according to an embodiment of the present invention are shown.

[0049] Figure 14 A microscope image of a gallium oxide single crystal sample grown in one step using a gallium oxide single crystal preparation method according to an embodiment of the present invention is shown.

[0050] Figure 15 The X-ray and neutron diffraction analysis results of a gallium oxide single crystal prepared according to an embodiment of the present invention are shown. (a) Partially shows the X-ray Laue pattern in the (0K 0) plane. (b) Partially includes the rocking curve measurement results, with the left curve of the relevant region showing X-ray diffraction data and the middle and right curves showing neutron diffraction data. (c) Partially shows the X-ray 2θ / θ scan data along the (H 0 0) direction.

[0051] Figure 16 Transmission electron microscopy (TEM) and atomic force microscopy (AFM) images of a gallium oxide single crystal prepared according to an embodiment of the present invention are shown. Part (a) shows an image of the (0b 0) plane of the gallium oxide single crystal measured using TEM and the electron diffraction pattern along the (0K 0) plane. Part (b) is a magnified TEM image (left side) of the area marked in (a), showing the unit lattice of the gallium oxide single crystal. A simplified illustration of the relevant unit lattice is also shown (right side). Part (c) shows an AFM image of the grown, undoped gallium oxide single crystal.

[0052] Figure 17 The results of measuring gallium oxide single crystals prepared according to an embodiment of the present invention using ultraviolet-visible-near-infrared spectrophotometry are shown.

[0053] Figure 18 The results of measuring gallium oxide single crystals prepared according to an embodiment of the present invention using secondary ion mass spectrometry are shown.

[0054] Figure 19 The diagram illustrates a conceptual diagram of a gallium oxide crystal preparation system and method according to an embodiment of the present invention. Detailed Implementation

[0055] The terminology used in this invention has been selected as widely used and common terms as possible while taking into account its function in this invention. However, it may vary depending on the intent of those skilled in the art, precedents, or the emergence of new technologies. Furthermore, in certain cases, terms may be arbitrarily chosen by the applicant; in such cases, their meanings will be described in detail in the description of the relevant invention. Therefore, the terminology used in this invention is not merely a name, but should be defined based on the meaning of the term and the entire content of this invention.

[0056] Unless otherwise defined, all terms used herein, including technical or scientific terms, shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms commonly used with the same meaning as defined in a dictionary shall be interpreted as having the meaning consistent with the context of the relevant description, and shall not be interpreted in an ideal or exaggerated sense unless explicitly defined in this application.

[0057] In the full text of the specification, when a part is mentioned as "including" a certain structural element, unless otherwise stated, it means that other structural elements may also be included, rather than excluding other structural elements.

[0058] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, so that those skilled in the art can easily implement the present invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein.

[0059] The present invention will now be described in detail.

[0060] The present invention provides an oxide single crystal preparation apparatus T, characterized in that it comprises: a heat source 100 for melting oxide particles; a growth section 200, made of refractory material, which is a space for loading the oxide particles and growing the oxide single crystal; a drive section 300 for moving the entire growth section to grow the oxide single crystal; and a measuring section 400 for measuring the temperature of the growth section throughout the entire process of the oxide single crystal growth.

[0061] like Figure 2As shown, the heat source unit 100 is characterized by comprising: a fuel gas supply unit 101; an oxygen supply unit 102; a pressure regulator 103 for adjusting the pressure of fuel injected into the fuel pipe; a pressure regulator 104 for adjusting the oxygen pressure; a premixing zone 107, which is a space for mixing the fuel gas and the oxygen; a fuel pipe 109 for allowing the fuel gas to flow into the premixing zone 107; a gas pipe 110 for allowing the oxygen to flow in; a fuel flow regulator 105 for adjusting the amount of fuel gas flowing into the premixing zone 107; an oxygen flow regulator 106 for adjusting the amount of oxygen; a nozzle 108 for releasing the mixture of fuel gas and oxygen in the premixing zone 107 to the outside; and a height adjuster 111 for adjusting the distance between the growth unit 200 and the nozzle 108.

[0062] The fuel gas used is a gas mainly composed of hydrocarbons, which may include hydrogen, propane, butane, acetylene, etc.

[0063] The fuel pressure regulator 103, oxygen pressure regulator 104, fuel flow regulator 105, and oxygen flow regulator 106 can be analog or digital devices, more preferably digital devices capable of communication, but are not limited thereto.

[0064] like Figure 3 As shown, the growth section 200 is characterized by comprising: a refractory and heat-insulating material 201 for creating an atmosphere independent of the heat generated by the heat source section 100 and the oxygen atmosphere of the surrounding air, and having heat resistance; oxide particles 202; a spark 204 for forming the heat and oxygen atmosphere generated from the heat source section 100; an oxide melt 203 formed by melting the oxide particles 202 heated by the spark; and an oxide single crystal 205 formed by slowly cooling and crystallizing the oxide melt 203.

[0065] According to one embodiment of the present invention, the oxide sample is subjected to strong gas pressure by a spark, so the sample is not prepared in powder form, but in granular form through cold pressing and sintering processes, thereby preventing the loss of raw materials and collecting the molten liquid without a furnace.

[0066] The refractory and heat insulation material 201 can be selected according to the melting point of the oxide to be melted. Preferably, it can be zirconium oxide, but it is not limited to this.

[0067] like Figure 4As shown, the drive unit 300 is characterized by comprising: a support 304 for supporting the growth unit 200; a conveyor belt 301 for linearly moving the entire support 304; a motor 302 for driving the conveyor belt 301; a microcontroller 303 for controlling the driving of the motor 302; and a computer C for controlling the microcontroller 303.

[0068] The refractory and heat-insulating material 201 and the oxide particles are characterized in that they are arranged in the following manner: both can be placed on a conveyor belt and the oxide particles are heated by sparks. After the temperature inside the refractory and heat-insulating material 201 reaches an equilibrium state, when the oxide particles generate molten liquid, the refractory and heat-insulating material 201 is moved horizontally in parallel by the conveyor belt.

[0069] During the growth of the oxide single crystal, the support 304, as the part exposed to high temperature, can be made of a metal material with a sufficiently high melting point to prevent damage. Preferably, it can be one or more materials selected from the group consisting of aluminum and stainless steel, but is not limited thereto.

[0070] The present invention is characterized in that the conveyor belt 301 is connected to the motor 302, the motor 302 is connected to the microcontroller 303, and the movement of the conveyor belt 301 is controlled by the microcontroller 303 and driven by the motor 302.

[0071] The present invention is characterized in that the microcontroller 303 is connected to the computer C and receives command signals from the program set on the computer C.

[0072] like Figure 5 As shown, the measuring unit 400 is characterized by including: an infrared camera 401 for measuring the temperature of the growth unit 200; and a computer C for receiving temperature data measured by the infrared camera.

[0073] The infrared camera 401 is characterized in that it measures the temperature of the growth section 200, transmits the temperature data of the growth section 200 to a computer in real time, and outputs it as an image through a program that can view real-time images.

[0074] Furthermore, the present invention is characterized in that, after the infrared camera 401 measures the temperature, if it is lower than the temperature set in the program, the fuel flow regulator 105 is adjusted by the algorithm control system to increase the temperature; if the temperature is higher than the temperature set in the program, the fuel flow regulator 105 is adjusted by the algorithm control system to decrease the temperature, thereby maintaining the set temperature.

[0075] Furthermore, the present invention provides a method for preparing gallium oxide single crystals, characterized by comprising: a sample preparation step S1, which prepares gallium oxide particles by processing gallium oxide powder; a growth preparation step S2, which creates a growth atmosphere and preheats the gallium oxide powder particles by loading them into an oxide single crystal preparation device; and a single crystal growth step S3, which grows the single crystal by driving a motor, thereby preparing gallium oxide single crystals.

[0076] like Figure 7 Part (a) and Figure 8 As shown, the sample preparation step S1 is characterized by including: a calcination step S110, removing organic impurities and moisture from the gallium oxide powder and converting the gallium oxide powder into β-phase gallium oxide powder; a mixing step S120, mixing the calcined gallium oxide powder; a cold pressing step S130, forming the mixed gallium oxide powder into compressed powder; and a sintering step S140, heat-treating the cold-pressed gallium oxide powder to form particles.

[0077] According to one embodiment of the present invention, the oxide sample is subjected to strong gas pressure by a spark, so the sample is not prepared in powder form, but in granular form through cold pressing and sintering processes, thereby preventing the loss of raw materials and collecting the molten liquid without a furnace.

[0078] Moreover, such as Figure 7 As shown in part (b), the growth atmosphere creation and preheating step S2 is characterized by comprising: a loading step S210, loading the gallium oxide particles prepared in the sample preparation step S1 into an oxide single crystal preparation apparatus; a pressure adjustment step S220, adjusting the pressure of the fuel gas and oxygen used for initial spark ignition; a flow rate adjustment step S230, adjusting the flow rate of the fuel gas and oxygen; an ignition step S240, generating a spark; a preheating step S250, preheating the growth section and the gallium oxide particles after raising the temperature to a temperature above the melting point of the gallium oxide particles; a ratio adjustment step S260, adjusting the ratio of the fuel gas to oxygen to create an oxygen atmosphere in the melting region of the gallium oxide particles; and a melting step S270, heating the sample to a temperature above the melting point of the gallium oxide particles.

[0079] like Figure 7As shown in section (c), the single crystal growth step S3 is characterized by comprising: a growth start step S310, in which a linear motor is driven to start the growth of a gallium oxide single crystal while the gallium oxide melt is prepared at a temperature above the melting point of the growth preparation step S2; a temperature holding step S320, in which the flow rate and pressure of the fuel gas and oxygen are adjusted to maintain the temperature of the growth section; an oxygen atmosphere holding step S330, in which the flow rate and pressure are adjusted to maintain the oxygen atmosphere of the growth section; a growth step S340, in which the gallium oxide single crystal is grown; a cooling step S350, in which the grown gallium oxide single crystal is cooled; and a single crystal extraction step S360, in which the gallium oxide single crystal grown on the gallium oxide particle is extracted.

[0080] The following describes a method for preparing gallium oxide single crystals according to an embodiment of the present invention, following the different steps.

[0081] The gallium oxide powder calcination step S110 is characterized by selecting a furnace material that does not react with the gallium oxide powder to form a new compound, loading the gallium oxide powder into the furnace, heating it to an appropriate temperature in the electric furnace and holding it for an appropriate time, and then naturally cooling it to atmospheric temperature without a cooling device.

[0082] The most suitable furnace material for containing the gallium oxide powder is platinum or a platinum-based alloy that does not chemically react with the gallium oxide powder.

[0083] like Figure 9 As shown, the present invention is characterized in that, in the gallium oxide powder calcination step S110, a platinum furnace containing 100g of gallium oxide powder is loaded into the circuit, heated to 1000°C for 6 hours and held at 1000°C for 20 hours, and then cooled to atmospheric temperature with the power supply of the furnace turned off.

[0084] like Figure 8 As shown, the raw material powder mixing step S120 is characterized by performing a grinding process to refine the particle size of the gallium oxide powder that has undergone the gallium oxide powder calcination step S110 and to make the particle size distribution uniform, thereby making the gallium oxide powder well mixed.

[0085] The grinding process can be carried out using a mortar and pestle or a ball mill or high-energy ball milling device. In this invention, approximately 90g to 100g of gallium oxide powder, which has undergone the calcination step S110, is ground in a mortar and pestle for 30 minutes.

[0086] The gallium oxide powder cold pressing step S130 is characterized in that the powder that has passed through the gallium oxide powder mixing step S120 is loaded into a mold made of a retractable alloy, and pressure is applied without heating to form particles.

[0087] In the cold pressing step S130, which is used to compress the mixed powder, 40g of gallium oxide powder from the gallium oxide powder mixing step S120 is loaded into a cylindrical mold made of stainless steel with a diameter of 1.5 inches. After being held at a pressure of 70 MPa for 5 minutes using a hydraulic press, the cold-pressed gallium oxide powder is separated. The cold pressing step can be performed twice in the same manner.

[0088] like Figure 10 As shown, the sintering step S140 is characterized in that a platinum furnace lid, which is not chemically reactive with the particles prepared by the gallium oxide powder cold pressing step S130, is used as a base to load the particles into the alumina furnace, as shown. Figure 11 As shown, the furnace is heated to 1450°C in an electric furnace for 8 hours and held at 1450°C for 20 hours before being cooled to atmospheric temperature with the power to the furnace turned off.

[0089] like Figure 3 As shown, the gallium oxide particle loading step S210 is characterized in that, after preparing two gallium oxide particles 202 prepared by the gallium oxide powder sintering step S140, the gallium oxide particles 202 are loaded at the bottom of the growth section 200 of the single crystal preparation apparatus T in a stacked manner, so as to prevent the molten liquid from overflowing to the bottom of the growth section 200 during the melting process.

[0090] The fuel gas and oxygen pressure regulation step S220 and the fuel gas and oxygen flow rate regulation step S230 are characterized in that they are regulated to have appropriate pressure and flow rate for the initial spark of ignition.

[0091] The spark ignition step S240 is characterized in that heat above the flash point is applied to the end of the nozzle 108 to generate a spark in the gas released from the nozzle 108. The fuel gas used in the spark ignition step S240 is portable LPG gas, a mixture of butane and propane in a 9:1 ratio.

[0092] The preheating step S250 is characterized in that, by adjusting the pressure and flow rate of fuel and oxygen, the gallium oxide particles 202 are slowly heated to a temperature close to the melting temperature of the gallium oxide particles 202 (1850°C) without causing them to crack due to thermal shock, and the temperature of the growth section 200 is maintained until thermal equilibrium is reached.

[0093] The oxygen atmosphere creation step S260 is characterized in that the oxygen partial pressure used to melt the gallium oxide particles 202 is maintained, and the oxygen pressure and flow rate are adjusted in order to maintain the temperature in the preheating step S250.

[0094] The melting step S270, which involves raising the temperature above the melting point of the gallium oxide particles to heat the sample, is characterized in that, in order to heat the sample above the melting point while maintaining the oxygen atmosphere formed in the oxygen atmosphere creation step S260, the gallium oxide particles 202 are melted by adjusting the flow rate and pressure of the fuel and oxygen, thereby preparing a gallium oxide melt 203.

[0095] In the melting step S270, a gallium oxide melt that can form a sufficient crystal size on the upper part of the gallium oxide particles 202 should be prepared, and the area of ​​the spark 205 with a higher melting point should be sufficiently large.

[0096] Furthermore, if the area of ​​the spark 205, which has a higher melting point than the diameter of the particle 202, is larger, the gallium oxide melt 203 will overflow to the bottom of the growth section 200. Therefore, the area of ​​the spark 205 should be maintained by appropriately adjusting the pressure and flow rate of the fuel gas and oxygen.

[0097] The linear motor driving step S310 and the single crystal growth step S320 are characterized in that when the gallium oxide melt 203 melted to above the melting point in the melting step S270 reaches a thermal equilibrium state inside the growth section 200, in order to grow gallium oxide single crystals, the linear motor should be driven and the temperature and oxygen atmosphere at the time of melting should be maintained by continuously adjusting the pressure and flow rate of fuel and oxygen.

[0098] In the linear motor driving step S310, the motor's moving speed can be from 0.3 mm / min to 0.7 mm / min, preferably 0.5 mm / min. The slower the motor's moving speed, the larger the crystal size and the better its quality.

[0099] According to one embodiment of the present invention, the temperature at which thermal equilibrium is reached in the linear motor driving step S310 is approximately 1950°C, the pressure of the fuel gas is approximately 0.05 MPa, and the pressure of the oxygen is approximately 0.02 MPa.

[0100] The single crystal growth step S320 is characterized in that, in order to maintain the temperature and oxygen atmosphere while the growth section 200 is placed entirely on the support 304 of the driving section 300 and moves along a straight line at a predetermined speed, such as... Figure 12 As shown, it is adjusted through an algorithm.

[0101] Furthermore, the cooling step S330 is characterized in that, when the gallium oxide single crystal growth ends, in order to reduce the temperature of the spark 204, the flow rate and pressure of fuel and oxygen are rapidly reduced, and in order to allow the temperature of the growth section 200 to slowly cool down to the ambient temperature, the upper part of the growth section 200 is covered with a refractory and heat-insulating material 201.

[0102] Furthermore, the single crystal extraction step S340 is characterized in that single crystals are screened by appropriately processing the gallium oxide single crystal 205 generated on the upper part of the gallium oxide particles 202 that have been cooled to atmospheric temperature.

[0103] Furthermore, the present invention provides gallium oxide single crystal, characterized in that it is prepared according to the above-described preparation method.

[0104] The present invention will be described in detail below by way of examples. However, the embodiments of the present invention can be modified into many other forms, and the scope of the present invention should not be construed as limited to the embodiments described below. The embodiments in this specification are provided only to illustrate the present invention more completely to those skilled in the art.

[0105] Example. Preparation of β-Ga2O3 crystals

[0106] 1. Preparation of β-Ga2O3 particles

[0107] (a) 100g of β-Ga2O3 powder was placed in the center of the electric furnace after being loaded into the platinum furnace.

[0108] (b) After heating in an electric furnace to 1000°C for 6 hours, maintain the temperature at 1000°C for 20 hours, and then allow it to cool naturally to atmospheric temperature with the power to the electric furnace turned off.

[0109] (c) Place the calcined β-Ga2O3 powder from (b) into a mortar and grind for 30 minutes.

[0110] (d) Place 40g of the β-Ga2O3 powder ground in (c) into a 1.5-inch diameter circular alloy mold and hold it at a pressure of 70 MPa for 5 minutes using a hydraulic press. Repeat this process twice.

[0111] (e) After placing two cold-pressed β-Ga2O3 powders taken out of the mold onto the lid of the platinum furnace and then into the alumina furnace, they are placed in the center of the electric furnace.

[0112] (f) Heat the furnace to 1450°C for 8 hours, maintain the temperature at 1450°C for 20 hours, and then allow it to cool naturally to atmospheric temperature with the furnace power off.

[0113] 2. Preparation of β-Ga₂O₃ single crystals

[0114] (g) Load the sintered β-Ga2O3 particles from (f) into the lower central part of the growth section.

[0115] (h) Using LPG fuel gas with a 9:1 ratio of propane and butane mixed with oxygen, open the valve of the gas tank and adjust the fuel gas pressure regulator and oxygen pressure regulator appropriately before igniting the spark.

[0116] (i) After spark ignition, the temperature of the spark is increased by opening the fuel gas flow meter and oxygen flow meter and adjusting the fuel gas pressure regulator and oxygen pressure regulator.

[0117] (j) To prevent the β-Ga₂O₃ particles from vaporizing and volatilizing when the spark temperature rises to around 1450°C by creating a high-oxygen atmosphere, a high-oxygen atmosphere is adopted... Figure 12 The algorithm shown is used to regulate the pressure gauge and flow meter. When β-Ga2O3 particles are exposed to a high-oxygen atmosphere, the powder is not vaporized but volatilized.

[0118] (k) When a high-oxygen atmosphere is formed at a temperature above 1450°C, the same method as (j) is used. Figure 12 The algorithm shown prepares a molten liquid by slowly increasing the flow rate and pressure of fuel gas and oxygen while melting β-Ga2O3 particles. After raising the temperature to 1950℃, it is held at the temperature for about 10 minutes to allow the system to reach thermal equilibrium.

[0119] (l) When a β-Ga2O3 molten liquid is generated and reaches thermal equilibrium to maintain a specified area of ​​molten liquid, single crystal growth is initiated by driving a motor. The motor is set to move the entire growth section at a speed of 0.5 mm / min.

[0120] (m) adopt Figure 12 The algorithm shown is adjusted to maintain a stable oxygen atmosphere at the growth thermometer until the single crystal growth is complete.

[0121] (n) After the growth of the single crystal is completed, the spark is extinguished and the temperature is slowly cooled.

[0122] (o) Extracting single crystals from the top of cooled β-Ga2O3 particles.

[0123] Experimental Example: Evaluation of β-Ga2O3 Crystals

[0124] As a β-Ga2O3 single crystal sample prepared according to an embodiment of the present invention Figure 14 The β-Ga2O3 single crystal sample shown is a microscopic photograph of a β-Ga2O3 single crystal sample grown in one step through the process described in the example (preparation of β-Ga2O3 crystal).

[0125] pass Figure 15The structure of a β-Ga2O3 single crystal sample prepared according to an embodiment of the present invention was observed using the results of single-crystal X-ray diffraction analysis and neutron diffraction analysis, as shown in parts (a), (b), and (c). Part (a) shows the X-ray Laue pattern of the (0K0) plane, with the (210) plane marked and shown on the pattern. Part (b) shows the rocking curve data, with X-ray data on the left and neutron data in the middle and right. The measured planes are (400), (020), and (002), and their half-widths are 0.12°, 0.14°, and 0.26°, respectively. Part (c) shows the X-ray 2θ / θ scan data along the (H00) direction.

[0126] Furthermore, the crystal structure and lattice constant of the β-Ga₂O₃ single crystal sample prepared according to an embodiment of the present invention were confirmed by single-crystal X-ray diffraction analysis, as shown in Table 1. Referring to Table 1, it can be confirmed that the crystal structure is monoclinic, and the lattice constant α is... b is c is α is 90°, β is 103.784°, γ is 90°, and the unit lattice volume is...

[0127] Table 1

[0128]

[0129] And, through Figure 16 The atomic arrangement and surface state of the β-Ga₂O₃ single crystal sample prepared according to an embodiment of the present invention are shown in parts (a), (b), and (c), as confirmed by transmission electron microscopy and atomic force microscopy. Part (a) shows the image observed along the (0b0) plane and the electron diffraction pattern along the (0K 0) plane, with peaks marked in the (201) and (400) directions on the electron diffraction pattern. Part (b) is a magnified transmission electron microscopy image (left) of the area marked in (a), with the unit lattice of the gallium oxide single crystal marked and a simplified diagram of the relevant unit lattice shown (right). Part (c) shows an atomic force microscopy image of the grown undoped β-Ga₂O₃, with a total horizontal length of 50 μm marked by a blue arrow, a surface roughness of 0.04 nm, and a step height along the direction marked by a red arrow, which corresponds to 0.5a of the β-Ga₂O₃ unit lattice, approximately 0.6 nm.

[0130] Furthermore, the β-Ga2O3 single crystal sample prepared according to an embodiment of the present invention was measured using ultraviolet-visible-near-infrared spectrophotometry, such as... Figure 17As shown, it can be confirmed that there is a direct bandgap value of 4.35 to 4.59 eV along the c* crystal axis and b crystal axis.

[0131] Furthermore, the β-Ga₂O₃ single crystal sample prepared according to an embodiment of the present invention was measured using secondary ion mass spectrometry, such as... Figure 18 As shown, the Si impurity level can be confirmed to be 2.28 × 10⁻⁶. 16 The Fe impurity content is 2.85 × 10⁻⁶. 16 The nitrogen impurity is 3.53 × 10⁻⁶. 15 The Sn impurity is 2.38 × 10⁻⁶. 16 .

[0132] Thus far, we have reviewed specific embodiments of the present invention. It will be understood by those skilled in the art that the present invention can be implemented in modified forms without departing from its essential characteristics. Therefore, the described embodiments should be understood in an illustrative manner rather than a limiting one. The scope of the present invention is shown within the scope of the claims, not in the foregoing description, and all differences within the equivalent scope should be interpreted as included in the present invention.

Claims

1. An apparatus for preparing oxide single crystals, characterized in that, include: The heat source section is used to melt oxide particles; The growth section, made of refractory material, is a space for loading the oxide particles and growing oxide single crystals. A driving section, which moves the entire growth section to enable the growth of the oxide single crystal; and A measuring section is used to measure the temperature of the growth section throughout the entire process of oxide single crystal growth.

2. The oxide single crystal preparation apparatus according to claim 1, characterized in that, The heat source includes: A fuel gas supply unit, wherein the fuel gas is composed of hydrocarbons; Oxygen Supply Department; A fuel pressure regulator is used to regulate the pressure of the fuel injected into the fuel line; An oxygen pressure regulator is used to regulate the pressure of oxygen. The premixing zone is the space in which the fuel gas and the oxygen are mixed; A fuel pipe allows the fuel gas to flow into the premixing zone. An oxygen tube allows the oxygen to flow in; A fuel flow regulator for regulating the amount of fuel gas flowing into the premixing zone; An oxygen flow regulator is used to regulate the amount of oxygen. The nozzle releases the mixture of fuel gas and oxygen in the premixed zone to the outside; and A height adjuster is used to adjust the distance between the growth section and the nozzle.

3. The oxide single crystal preparation apparatus according to claim 1, characterized in that, The growth section includes refractory and heat-insulating materials to create an atmosphere independent of the heat generated by the heat source section and the oxygen atmosphere of the surrounding air, and has heat resistance.

4. The oxide single crystal preparation apparatus according to claim 1, characterized in that, The drive unit includes: A support frame is used to support the growth section; The conveyor belt enables the entire support structure to move linearly. A motor is used to drive the conveyor belt; A microcontroller for controlling the drive of the motor; and A computer for controlling the microcontroller.

5. The oxide single crystal preparation apparatus according to claim 1, characterized in that, The measuring unit includes: An infrared camera is used to measure the temperature of the growth section; and A computer is used to receive temperature data measured by the infrared camera.

6. A method for preparing gallium oxide single crystals, characterized in that, include: The sample preparation step involves preparing gallium oxide particles by processing gallium oxide powder; The growth preparation step involves creating a growth atmosphere and preheating the device by loading the gallium oxide powder particles into the oxide single crystal fabrication apparatus; and The single crystal growth step involves using a driving motor to grow a single crystal, thereby preparing gallium oxide single crystals.

7. The method for preparing gallium oxide single crystals according to claim 6, characterized in that, The sample preparation steps include: The calcination step removes organic impurities and moisture from the gallium oxide powder and converts the gallium oxide powder into β-phase gallium oxide powder. The mixing step involves mixing the calcined gallium oxide powder. The cold pressing step compresses the mixed gallium oxide powder into a compressed powder; and The sintering step involves heat-treating the cold-pressed gallium oxide powder to form particles.

8. The method for preparing gallium oxide single crystals according to claim 6, characterized in that, The growth preparation steps include: The loading step involves loading the gallium oxide particles prepared in the sample preparation step into the oxide single crystal preparation apparatus. The pressure regulation step regulates the pressure of the fuel gas and oxygen used for initial spark ignition; The flow regulation step involves regulating the flow rates of the fuel gas and oxygen. The ignition process generates a spark; The preheating step involves heating the growth section and the gallium oxide particles to a temperature before their melting point. The proportioning adjustment step involves adjusting the ratio of the fuel gas to oxygen to create an oxygen atmosphere in the molten region of the gallium oxide particles; and The melting step involves heating the sample to a temperature above the melting point of the gallium oxide particles.

9. The method for preparing gallium oxide single crystals according to claim 6, characterized in that, The single crystal growth step includes: The growth step begins by driving a linear motor to start the growth of gallium oxide single crystals while the gallium oxide melt is prepared at a temperature above the melting point of the growth preparation step. The temperature maintenance step involves adjusting the flow rate and pressure of the fuel gas and oxygen to maintain the temperature of the growth section. The oxygen atmosphere maintenance step involves adjusting the flow rate and pressure to maintain an oxygen atmosphere in the growth section. The growth step is used to grow the gallium oxide single crystal. The cooling step involves cooling the gallium oxide single crystal after its growth is complete; and The single crystal extraction step extracts the gallium oxide single crystal grown on the gallium oxide particles.

10. A gallium oxide single crystal, characterized in that, Gallium oxide single crystals are prepared using the method described in claim 6.

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