Patent Application
20240417881
The present invention relates to a method for producing a β-Ga2O3/β-Ga2O3 multilayer body and a multilayer body obtained by said method.
Power devices are one of the key devices for improving power usage efficiency to realize a low-carbon society, and are mainly used as elements to configure inverters that convert DC-AC power and adjust AC voltage and frequency. Upon the above-mentioned conversion, energy loss due to the resistance when current flows through the element and generation of wasted current due to the recovery process of charge distribution in the element, which occurs at the moment when the voltage applied to the element is switched, are inevitable. These loss percentages vary with power and frequency, but generally range from a few percent to about a dozen percent. Element structures of conventional Si-based power semiconductors have been devised but further improvement of efficiency is becoming difficult because Si is approaching its physical property limit. Therefore, SiC and GaN are being developed as alternative power device materials to Si. SiC and GaN have band gaps of 3.3 eV and 3.4 eV, respectively, and they are materials having wider band gaps than the band gap of Si (i.e., 1.1 eV). The wider the band gap of a material, the higher the breakdown voltage, which represents the electric field at the boundary where charge is prevented from flowing into the semiconductor (avalanche breakdown), and thus the material can provide a device structure that can withstand higher voltages.
β-Ga2O3 is a kind of oxide semiconductor that has been adopted to transparent conductive substrates for GaN-based LEDs, solar-blind UV detectors, etc. Recently, it has attracted attention as a material for power devices and is expected to realize high-voltage and high-efficiency power semiconductors that surpass SiC and GaN. This is due to the fact that the band gap of β-Ga2O3 is expected to be 4.5-4.9 eV, which is wider than those of SiC and GaN. Another advantage of β-Ga2O3 over SiC and GaN is that it allows growing a crystal from a melt. SiC and GaN have difficulty in growing a crystal from a melt, and have an issue that their substrates are expensive. On the other hand, β-Ga2O3 has a melting point at normal pressure, allows bulk crystal growth, and its study and development are progressing through the EFG (Edge-Defined Film-fed Growth) method and the vertical Bridgman method. The former growth method has provided commercially available 2- to 4-inch substrates, and the latter is used for the development of 4-inch substrates.
In order to apply β-Ga2O3 to power devices, a β-Ga2O3 (epitaxial layer)/β-Ga2O3 (substrate) multilayer body consisting of two layers of β-Ga2O3 with different residual electron densities is required. The thickness of the epitaxial layer needs to be around several μm to 20 μm, and vapor-phase growth methods such as metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), mist CVD, and halide vapor-phase epitaxy (HVPE) have traditionally been used. However, the vapor-phase growth method is a non-thermodynamic growth method and has the disadvantages of poor crystal quality and slow growth rate.
For example, Non-patent literature 1 discloses a method of epitaxial growth of β-Ga2O3 on a sapphire substrate by the HVPE method. According to this method, the sapphire substrate and β-Ga2O3 have different crystal structures, resulting in multiple rotational domains and an epitaxial layer that is not composed of a single domain. This layer is not strictly a single crystal and cannot be used for power devices. The full width at half maximum of the X-ray rocking curve of the epitaxial layer obtained by the same method is as high as 0.5 deg (1,800 arcsec), indicating low crystallinity. Patent literature 1 also discloses a method of epitaxial growth of β-Ga2O3 on a β-Ga2O3 substrate by the HVPE method to obtain a β-Ga2O3/β-Ga2O3 multilayer body (hereinafter simply referred to as a “β-Ga2O3 multilayer body”). Although a β-Ga2O3/β-Ga2O3 multilayer body can be obtained by this method, the growth rate of the epitaxial layer is as low as 2.7-6.0 μm/hr.
On the other hand, the liquid-phase growth method has the advantage of producing a high-quality crystal more easily than the vapor-phase growth method because crystal growth proceeds in principle in thermal equilibrium. The melting point of β-Ga2O3 is as high as 1970° C., and it is difficult to maintain a stable melt surface near the melting point, making it difficult to grow β-Ga2O3 by the Czochralski method, which is employed for single-crystal silicon and the like. Therefore, a single crystal is grown by the above-mentioned EFG method or vertical Bridgman method. However, a β-Ga2O3 multilayer body cannot be obtained by the EFG or the vertical Bridgman method. Examples of a method in which a target substance is dissolved in a suitable solvent, the temperature of the mixed solution is lowered to a supersaturated state, and the target substance is grown from the melt include the static slow-cooling method, the flux method, the floating zone method, the top seeded solution growth (TSSG) method, the solution pulling method, and the liquid-phase epitaxy (LPE) method.
Patent literature 2 discloses a method for obtaining a β-Ga2O3 epitaxial layer by the LPE method. According to this method, a β-Ga2O3 single-crystal layer is stacked on a sapphire substrate by the LPE method, and a β-Ga2O3 multilayer body cannot be obtained because the substrate is made of sapphire. Moreover, the crystal structure of the sapphire substrate is corundum, while the crystal structure of β-Ga2O3 is monoclinic, and so they have different crystal structures. In addition, there is a problem of poor crystal quality due to inconsistent lattice constants.
When a β-Ga2O3 single-crystal layer is grown by the liquid-phase growth method such as the LPE method, a solvent capable of dissolving β-Ga2O3 is required. In Patent literature 2, PbO and PbF2 are exemplified as solvents, and either one of them is used. In order to establish a stable and well reproducible single-crystal growth method, it is common practice to keep the melt at a temperature about 100-200° C. above its melting point so that the solvent and solute are mixed homogeneously. In Patent literature 2, the melt is maintained at 1100° C. The melting points of PbO and PbF2 are about 886° C. and 824° C., respectively. In general, when the temperature of the melt containing either PbO or PbF2 exceeds 1000° C., some of PbO or PbF2 volatilizes and the composition of the melt changes, which is not favorable for growing a β-Ga2O3 single crystal in a stable and well reproducible manner. In addition, since the vaporized PbO or PbF2 reacts with the furnace material constituting the crystal growing furnace, the number of times the furnace material can be used is reduced and toxic Pb is volatilized, which increase the cost because the crystal growing furnace needs to have a closed structure or the like.
As described above, as a method for obtaining a β-Ga2O3 multilayer body that is useful for power devices, methods employing vapor-phase growth of β-Ga2O3 on a β-Ga2O3 substrate have the disadvantages of poor crystal quality and slow growth rate. Alternatively, when a liquid-phase growth method is used, which in principle is close to thermal equilibrium growth and which is expected to result in high crystallinity and high growth rate, there is a problem where a β-Ga2O3 multilayer body cannot be obtained by a conventional method. In addition, use of either PbO or PbF2 as a solvent and the high vapor pressure of the conventional liquid-phase growth method make it difficult to grow a β-Ga2O3 single crystal in a stable and cost-effective manner.
The present invention has an objective of solving at least one of the above-described conventional problems. Further, the present invention has an objective of providing a method for producing a β-Ga2O3/β-Ga2O3 multilayer body by stacking a β-Ga2O3 single crystal having high crystallinity and fast growth rate on a β-Ga2O3 substrate by a liquid-phase epitaxial growth method.
Herein, a β-Ga2O3/β-Ga2O3 multilayer body refers to a multilayer body in which an epitaxial layer containing β-Ga2O3 is stacked on a substrate containing β-Ga2O3.
The present inventors have diligently studied to solve the above problems and found that the above problems can be solved by the following invention. Accordingly, the present invention is as follows.
<1> A method for producing a β-Ga2O3/β-Ga2O3 multilayer body, the method comprising mixing and melting Ga2O3 as a solute and PbO and Bi2O3 as solvents, then bringing a D-Ga2O3 substrate into direct contact with the resulting melt, and allowing a β-Ga2O3 single crystal to grow on the β-Ga2O3 substrate by a liquid-phase epitaxial growth method, thereby obtaining the β-Ga2O3/β-Ga2O3 multilayer body.
<2> The method for producing a β-Ga2O3/β-Ga2O3 multilayer body according to <1> above, wherein the mixing ratio of Ga2O3 as the solute to PbO and Bi2O3 as the solvents is solute: solvents=5-30 mol %: 95-70 mol %, and the mixing ratio of the solvents, PbO and Bi2O3, is PbO: Bi2O3=0.1-95 mol %: 99.9-5 mol %.
<3> A method for producing a β-Ga2O3/β-Ga2O3 multilayer body, the method comprising mixing and melting Ga2O3 as a solute and PbO and PbF2 as solvents, then bringing a D-Ga2O3 substrate into direct contact with the resulting melt, and allowing a β-Ga2O3 single crystal to grow on the β-Ga2O3 substrate by a liquid-phase epitaxial growth method, thereby obtaining the β-Ga2O3/β-Ga2O3 multilayer body.
<4> The method for producing a β-Ga2O3/β-Ga2O3 multilayer body according to <3> above, wherein the mixing ratio of Ga2O3 as the solute to PbO and PbF2 as the solvents is solute: solvents=2-20 mol %: 98-80 mol %, and the mixing ratio of the solvents, PbO and PbF2, is PbO:PbF2=2-80 mol %: 98-20 mol %.
<5> The method for producing a β-Ga2O3/β-Ga2O3 multilayer body according to any one of <1> to <4> above, wherein the layer containing the β-Ga2O3 single crystal formed by the liquid-phase epitaxial growth method comprises foreign elements in total amount of 0.01 mol % or more but 20 mol % or less.
<6> The method for producing a β-Ga2O3/β-Ga2O3 multilayer body according to <5> above, wherein the foreign element is one or more selected from the group consisting of Be, Mg, Ca, Sr, Ba, Ti, Zr, Hf, Fe, Co, Ni, Cu, Zn, Cd, Al, In, Si, Ge, Sn, and Pb.
<7> A β-Ga2O3/β-Ga2O3 multilayer body comprising a layer containing a β-Ga2O3 single crystal on a β-Ga2O3 substrate, wherein the full width at half maximum of the rocking curve of the layer containing the β-Ga2O3 single crystal is 5-100 arcsec.
According to a preferred embodiment of the present invention, evaporation of the solvent is suppressed, and stable crystal growth with minimal composition fluctuation can be achieved. Moreover, the consumption of furnace materials is reduced, and it is not necessary for the growth furnace to be a closed system, thereby enabling manufacturing at a lower cost. In addition, since the liquid-phase growth method is used as the crystal growth method, a β-Ga2O3 single-crystal layer can be grown with high crystallinity at a high growth rate. The β-Ga2O3 multilayer body produced by this embodiment can be used for power devices using β-Ga2O3 multilayer bodies that are expected to be developed in the future.
A first embodiment of the present invention is a method for producing a β-Ga2O3/β-Ga2O3 multilayer body, the method comprising mixing and melting Ga2O3 as a solute and PbO and Bi2O3 as solvents, then bringing a β-Ga2O3 substrate into direct contact with the resulting melt, and allowing a β-Ga2O3 single crystal to grow on the β-Ga2O3 substrate by a liquid-phase epitaxial growth method, thereby obtaining the β-Ga2O3/β-Ga2O3 multilayer body.
Hereinafter, the principle of the first embodiment of the present invention will be described.
The solvent composition is preferably PbO: Bi2O3=0.1-95 mol %: 99.9-5 mol %. More preferably, the solvent composition is PbO: Bi2O3=20-90 mol %: 80-10 mol %, and particularly preferably PbO: Bi2O3=50-80 mol %: 50-20 mol %. Since the LPE growth temperature (temperature at the time of epitaxial growth) is higher when PbO or Bi2O3 alone is used as the solvent, a mixed solvent such as the one mentioned above is favorable.
The mixing ratio of Ga2O3 as the solute and PbO and Bi2O3 as the solvents is preferably solute: solvents=5-30 mol %: 95-70 mol %. More preferably, the solute concentration is 14 mol % or more but 27 mol % or less. Solute concentrations lower than 5 mol % may result in a slow crystal growth rate while solute concentrations higher than 30 mol % may result in a high LPE growth temperature and increased solvent volatilization. It may also result in a faster crystal growth rate and poor crystal quality.
In the first embodiment of the present invention, the growth rate of the layer containing a β-Ga2O3 single crystal (epitaxial layer) formed by the liquid-phase epitaxial growth method is preferably 10-50 μm/hr, and more preferably 20-30 μm/hr. Growth rates lower than 10 μm/hr may result in a slow growth rate and increased cost. In addition, growth rates higher than 50 μm may result in poor crystal quality. Here, the growth rate can be obtained from the difference in film thickness before and after LPE growth and the growth time.
Next, a second embodiment of the present invention is a method for producing a β-Ga2O3/β-Ga2O3 multilayer body, the method comprising mixing and melting Ga2O3 as a solute and PbO and PbF2 as solvents, then bringing a β-Ga2O3 substrate into direct contact with the resulting melt, and allowing a β-Ga2O3 single crystal to grow on the β-Ga2O3 substrate by a liquid-phase epitaxial growth method, thereby obtaining the β-Ga2O3/β-Ga2O3 multilayer body.
The principle of the second embodiment of the present invention will be described.
The solvent composition is preferably PbO:PbF2=2-80 mol %: 98-20 mol %. More preferably, the solvent composition is PbO:PbF2=20-80 mol %: 80-20 mol %, and particularly preferably PbO:PbF2=40-60 mol %: 60-40 mol %. Since the LPE growth temperature is higher when PbO or PbF2 alone is used as the solvent, a mixed solvent such as the one mentioned above is favorable.
The mixing ratio of Ga2O3 as the solute and PbO and PbF2 as the solvents is preferably solute: solvents=2-20 mol %: 98-80 mol %. More preferably, the solute concentration is 10 mol % or more but 20 mol % or less. Solute concentrations lower than 2 mol % may result in a slow growth rate while solute concentrations higher than 20 mol % may result in a high LPE growth temperature and increased solvent volatilization. It may also result in a faster crystal growth rate and poor crystal quality.
In the second embodiment of the present invention, the growth rate of the layer containing a β-Ga2O3 single crystal (epitaxial layer) formed by the liquid-phase epitaxial growth method is preferably 10-50 μm/hr, and more preferably 20-30 μm/hr. Growth rates lower than 10 μm/hr may result in a slow growth rate and increased cost. In addition, growth rates higher than 50 μm may result in poor crystal quality. Here, the growth rate can be obtained from the difference in film thickness before and after LPE growth and the growth time.
In the first and second embodiments of the present invention, for the purposes of controlling the LPE growth temperature, adjusting the solvent viscosity, and doping foreign elements, one or more third components can be added to the solvent to the extent that the solubility of Ga2O3 and the amount of PbO+Bi2O3 or PbO+PbF2 vaporization are not significantly changed. Examples of the third component include B2O3, V2O5, P2O5, MoO3, and WO3. Bi2O3 may also be added as a third component to the solvent of the second embodiment.
The most preferred growth method for a β-Ga2O3 multilayer body according to the present invention is a liquid-phase epitaxial growth method using a β-Ga2O3 substrate.
In a β-Ga2O3 multilayer body useful as a power device, the residual electron density in the epitaxial layer needs to be controlled. Ga in β-Ga2O3 is a trivalent oxide and generally exhibits n-type conductivity. In the first and second embodiments of the present invention, the residual electron density, band gap, insulating property, etc. can be imparted by doping a foreign element into β-Ga2O3. For example, doping divalent impurities MgO or ZnO into β-Ga2O3 can reduce the residual electrons. On the other hand, the residual electron density can be increased by doping tetravalent impurities SiO2 or SnO2. In addition, Fe2O3 doping can provide an insulating property. Meanwhile, the band gap can be increased by doping MgO or Al2O3, which has a wider band gap than β-Ga2O3, to obtain a mixed crystal. On the other hand, the band gap can be reduced by doping ZnO or CdO to obtain a mixed crystal.
A layer containing the β-Ga2O3 single crystal formed by the liquid-phase epitaxial growth method contains, one or more foreign elements selected from the group consisting of Be, Mg, Ca, Sr, Ba, Ti, Zr, Hf, Fe, Co, Ni, Cu, Zn, Cd, Al, In, Si, Ge, Sn, and Pb, preferably in the range of 0.01-20 mol %, more preferably in the range of 0.1-10 mol %. Doping amounts of foreign elements less than 0.01 mol % may result in poor properties, and doping amounts greater than 20 mol % may cause difficulties in crystal growth.
A third embodiment of the present invention is a β-Ga2O3/β-Ga2O3 multilayer body having a layer containing a β-Ga2O3 single crystal on a β-Ga2O3 substrate, wherein the full width at half maximum of the rocking curve of the layer containing the β-Ga2O3 single crystal is 5-100 arcsec.
The above-described β-Ga2O3/β-Ga2O3 multilayer body of the present invention can favorably be produced by the first and second embodiments of the present invention described above.
According to the present invention, the full width at half maximum of the rocking curve of the layer containing the β-Ga2O3 single crystal is 5-100 arcsec, preferably 5-80 arcsec, and more preferably 5-50 arcsec. The full width at half maximum above 100 arcsec may result in low crystallinity and performance of the power device may be degraded. The β-Ga2O3/β-Ga2O3 multilayer body of the present invention is characterized by its high crystallinity. In the present invention, the method described in the examples described below can be adopted as the method for measuring a full width at half maximum of a rocking curve.
Hereinafter, a method of depositing a β-Ga2O3 epitaxial layer on a β-Ga2O3 substrate will be described as a method for growing a β-Ga2O3/β-Ga2O3 multilayer body according to one embodiment of the present invention. The present invention should not be limited in any way to the following examples.
Hereinafter, an exemplary production method of the present invention will be described with reference to
A platinum crucible 7, in which raw materials are melted and stored as a melt 8, is placed on a crucible stand 9. Three-stage side heaters (upper heater 1, middle heater 2, and lower heater 3) that heat and melt the raw materials in the platinum crucible 7 are provided outside and to the side of the platinum crucible 7. The heater outputs are independently controlled, and the amount of heat applied to the melt 8 is independently adjusted. A furnace core tube 11 is placed between the heaters and the inner wall of the production furnace, and a furnace lid 12 is placed above the furnace core tube 11. A pull-up mechanism is provided above the platinum crucible 7. An alumina growing shaft 5 is secured to the pull-up mechanism, and a substrate holder 6 and a substrate 4 (β-Ga2O3 substrate) secured by the holder are provided at one end of the shaft. A mechanism for rotating the shaft is provided at the top of the growing shaft 5. In addition, a thermocouple 10 is provided at the bottom of the crucible.
In order to melt the raw materials in the platinum crucible 7, the production furnace is heated until the raw materials are melted. Preferably, the temperature is raised to 600-1000° C., more preferably to 700-900° C., and the raw material melt is allowed to stand for 2-3 hours to homogenize. Instead of leaving it stationary, a platinum plate attached to one end of the alumina shaft can be immersed in the melt to stir and homogenize the melt by rotating the shaft. It is desirable to allow a β-Ga2O3 single-crystal layer to grow only directly below the substrate. If the growth of the β-Ga2O3 single crystal occurs in the melt where it is not directly below the substrate, the grown single crystal will adhere to the substrate by convection currents in the melt, resulting in phases with different growth orientations, which is undesirable. Therefore, a temperature gradient is applied to the three-stage heaters so that the temperature of the crucible bottom is a few degrees higher than that of the melt surface. After the temperature of the melt has stabilized, a seed crystal substrate is brought into contact with the melt surface. After the seed crystal substrate comes into uniform contact with the melt, the temperature is kept constant, or the temperature is lowered at a rate of 0.025-5° C./hr, to allow a β-Ga2O3 single-crystal layer of interest to grow on the surface of the seed crystal substrate. During the growth, the seed crystal substrate is rotated at 5-300 rpm by the rotation of the growing shaft, and the rotation direction is reversed at regular intervals. After allowing a crystal to grow for about 30 minutes to 24 hours, the growing shaft is lifted to separate the grown crystal from the melt, and the melt attached to the surface of the grown crystal is removed by rotating the growing shaft at 50 to 300 rpm. The temperature is then allowed to cool to room temperature over a period of 1-24 hours to obtain the desired β-Ga2O3/β2O3 multilayer body.
A platinum crucible 7 with inner diameter of 120 mm, height of 150 mm, and thickness of 1 mm was filled with 2661.2 g of PbO (purity: 99.999%), 2777.7 g of Bi2O3 (purity: 99.999%), and 561.2 g of Ga2O3 (purity: 99.999%) as raw materials. The mixing ratio of Ga2O3 as the solute to PbO and Bi2O3 as the solvents was solute: solvents=14.3 mol %: 85.7 mol %, and the mixing ratio of the solvents, PbO and Bi2O3, was PbO: Bi2O3-67 mol %: 33 mol %. The platinum crucible 7 fed with the raw materials was placed in a LPE furnace shown in
Attempts were made to produce β-Ga2O3/β2O3 multilayer bodies in the same manner as in Example 1 except that the composition of the feed was changed to give the composition shown in Table 1 below, and the temperature at which the raw materials were melted, and the growth temperature were changed as shown in Table 1.
Here, the crystallinity of the epitaxial layer of the β-Ga2O3/β2O3 multilayer body obtained in Example 1 was evaluated by the full width at half maximum of the rocking curve of the (002) plane. The result is shown in
β-Ga2O3/β-Ga2O3 multilayer bodies were obtained in the same manner as in Example 1 except that the composition of the feed was changed to give the composition shown in Table 1 below, and the temperature at which the raw materials were melted and the growth temperature were changed as shown in Table 1. The epitaxial layer obtained in Example 2 was a mixed layer of β-Ga2O3 and MgO, and the epitaxial layer obtained in Example 5 was a mixed layer of β-Ga2O3 and Al2O3.
As described above, a β-Ga2O3/β-Ga2O3 multilayer body can be produced by mixing and melting Ga2O3 as a solute and PbO and Bi2O3 as solvents, then bringing a β-Ga2O3 substrate into direct contact with the resulting melt. As can be appreciated by comparing Examples 1-8 with Comparative examples 1-2, the melting point of the solvent can be lowered by mixing PbO and Bi2O3 compared to PbO or Bi2O3 alone. Therefore, both the temperature at which the raw materials were melted and the growth temperature of β-Ga2O3 were lower than those in the case of using a single solvent. This means that the amount of vaporization of the solvent components can be reduced. According to this method, since evaporation of the solvent is suppressed, stable crystal growth with minimal composition fluctuation can be achieved. Moreover, the consumption of furnace materials is reduced, and it is not necessary for the growth furnace to be a closed system, thereby enabling manufacturing at a lower cost. In addition, as mentioned above, the present invention is a liquid-phase growth method that is close to thermal equilibrium growth. Therefore, as shown in Table 1 above, the growth rate was as fast as 13-30 μm/hr, and the full width at half maximum of the rocking curve was as narrow as 15-28 arcsec, showing high crystallinity. On the other hand, in Comparative examples 1-2, multilayer bodies were not produced because the raw materials did not melt unless the heat applied was higher than 1000° C. and the solvent volatilized at a temperature higher than 1000° C.
A platinum crucible 7 with an inner diameter of 120 mm, a height of 150 mm, and a thickness of 1 mm was filled with 1022.3 g of PbO (purity: 99.999%), 4503.7 g of PbF2 (99%), and 476.2 g of β-Ga2O3 as raw materials. The mixing ratio of Ga2O3 as the solute to PbO and PbF2 as the solvents was solute: solvents=10.0 mol %: 90 mol %, and the mixing ratio of the solvents, PbO and PbF2, was PbO:PbF2=20 mol %: 80 mol %. The platinum crucible 7 fed with the raw materials was placed in a LPE furnace shown in
β-Ga2O3/β-Ga2O3 multilayer bodies were obtained in the same manner as in Example 9 except that the composition of the feed was changed to give the composition shown in Table 2 below, and the temperature at which the raw materials were melted and the growth temperature were changed as shown in Table 2.
β-Ga2O3/β-Ga2O3 multilayer bodies were obtained in the same manner as in Example 9 except that the composition of the feed was changed to give the composition shown in Table 3 below, and the temperature at which the raw materials were melted and the growth temperature were changed as shown in Table 3. If the concentration of Ga2O3 as the solute is lower than 2 mol %, the melting point becomes closer to the melting point of the solvent, and stable crystal growth may be difficult due to the viscosity of the solvent. Moreover, a solute concentration higher than 20 mol % may result in a high growth temperature. Therefore, the concentration of Ga2O3 as the solute is preferably 2-20 mol %.
As described above, a β-Ga2O3/β2O3 multilayer body can be produced by mixing and melting Ga2O3 as a solute and PbO and PbF2 as solvents, then bringing a β-Ga2O3 substrate into direct contact with the resulting melt. As can be appreciated by comparing Examples 9-13 with Comparative examples 1 and 3, the melting point of the solvent can be lowered by mixing PbO and PbF2 compared to PbO or PbF2 alone. Therefore, both the temperature at which the raw materials were melted and the growth temperature of β-Ga2O3 were lower than those in the case of using a single solvent. This means that the amount of vaporization of the solvent components can be reduced. According to this method, since the amount of evaporation of the solvent is suppressed, stable crystal growth with minimal composition fluctuation can be achieved. Moreover, the consumption of furnace materials is reduced, and it is not necessary for the growth furnace to be a closed system, thereby enabling manufacturing at a lower cost. In addition, as mentioned above, the present invention is a liquid-phase growth method that is close to thermal equilibrium growth. Therefore, as shown in Tables 2 and 3 above, the growth rate was as fast as 18-29 μm/hr, and the full width at half maximum of the rocking curve was as narrow as 35-77 arcsec, showing high crystallinity. On the other hand, in Comparative example 3, a multilayer body was not produced because the raw materials did not melt unless the heat applied was higher than 1000° C. and the solvent volatilized at a temperature higher than 1000° C.
As described above, in each of Examples 1-13, the full width at half maximum of the rocking curve of the (002) plane of the β-Ga2O3 epitaxial layer obtained by the LPE method was 15-77 arcsec, showing extremely high crystalline.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-178650 | Nov 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/040309 | 10/28/2022 | WO |
