Growth method for increasing size of gallium oxide crystal

Abstract

The invention discloses a growth method for increasing the size of a gallium oxide crystal, and belongs to the technical field of crystal growth. The gas inlet with the lower end connected with the oxygen pipeline is formed in the middle of the bottom of the crucible, the flow valve on the oxygen pipeline is opened during crystal growth, the temperature of oxygen filled into the crucible is controlled to be lower than the melt temperature through the heater, and the temperature difference between the middle of the crystal and the edge of the crystal can be reduced due to the influence of oxygen bringing a cold source; and polycrystallization caused by overlarge internal and external temperature difference after overlarge crystal size is avoided. Moreover, oxygen in the crucible can be fully mixed with the melt, and gallium oxide is subjected to reversible decomposition reaction and inclines leftwards, so that gallium is not decomposed from the gallium oxide melt any more, and the crucible cannot be corroded by gallium. And after the gallium oxide melt is not decomposed any more, volatilization can be effectively inhibited, and the temperature performance of a thermal field is improved. Therefore, the technical problems that in the gallium oxide crystal growth process, polycrystallization is likely to happen, gallium oxide is likely to volatilize, and the crucible is likely to be corroded, so that the crystal growth size is affected are effectively solved.

Description

Technical Field

[0001] The present invention relates to the field of crystal growth technology, and more particularly to a growth method for increasing the size of gallium oxide crystals. Background Art

[0002] At present, the mainstream growth method of gallium oxide is the melt method, which is a growth method in which the gallium oxide raw material and its dopants are melted into a melt in a crucible and then recrystallized. The melt method is specifically subdivided into guided mold method, pulling method, casting method, VHGF method and VB method. Iridium crucible is the mainstream crucible currently used to grow gallium oxide crystals, but due to the excessive density of gallium oxide melt and the corrosiveness of decomposed gallium, the brittleness of iridium itself and the easy corrosion at high temperature make it difficult for iridium crucible to carry deeper gallium oxide melt, so that it cannot be invested in production raw materials in large quantities, which in turn affects the size of gallium oxide crystals. In addition, gallium oxide melt is more likely to volatilize after decomposition, and volatiles are easily adhered to the temperature field, changing the insulation coefficient, thereby affecting the temperature gradient distribution of the temperature field, and then affecting the crystal size. At present, the method of suppressing the volatilization of gallium oxide is mainly achieved through the atmosphere environment, and the suppression effect is not obvious. In addition, gallium oxide has poor heat dissipation capacity, which increases the temperature difference between the middle and edge of the crystal. The stress caused by the temperature difference easily causes the crystal to become polycrystalline, which in turn affects the growth size of the crystal.

[0003] Therefore, there is an urgent need for a technical solution that can solve the problem of the growth size of gallium oxide crystals being affected by polycrystallization, volatilization of gallium oxide, and corrosion of crucibles during the growth process. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a growth method for increasing the size of gallium oxide crystals.

[0005] The invention provides a growth method for increasing the size of gallium oxide crystals, comprising: adding a gallium oxide raw material and a dopant into a crucible, and then heating the crucible until the gallium oxide raw material is melted into a melt; wherein an air inlet is pre-opened at the middle position of the bottom of the crucible, an oxygen pipeline is connected below the air inlet, and a first heater and a flow valve are arranged on the oxygen pipeline; the flow valve is opened and the temperature of oxygen entering the oxygen pipeline is adjusted to be lower than the temperature of the melt through the first heater, and the oxygen in the oxygen pipeline enters the crucible through the air inlet; the heating power of the crucible is gradually reduced at a first rate, and the flow rate of oxygen entering the crucible is gradually reduced at a second rate until the melt is exhausted; wherein the first rate is 30-60w / h, and the second rate is 4-6% / h; the heating power of the crucible is gradually reduced at a third rate, and after the crucible is cooled to room temperature, the crystal growth is terminated; wherein the third rate is 100-150w / h.

[0006] Optionally, the air inlet is a multi-hole air inlet.

[0007] Optionally, before heating the crucible until the gallium oxide raw material is melted into a melt, the method further comprises: adding a liquid sealing agent into the crucible.

[0008] Optionally, the method further comprises: after the crystal growth is finished, placing the crucible into an ultrasonic machine, turning on the ultrasonic and heating functions of the ultrasonic machine, and turning off the ultrasonic machine after the liquid sealing agent melts.

[0009] Optionally, a check valve located above the heater and the flow valve is also provided on the oxygen pipeline.

[0010] Optionally, the crucible is in the shape of a parallelepiped.

[0011] Optionally, the outside of the crucible has an anti-deformation coating.

[0012] Optionally, the crucible has an anti-corrosion coating on the inside.

[0013] Optionally, a temperature field is arranged around the crucible, a second heater for heating the crucible is arranged outside the temperature field, and the temperature field outside the crucible is arranged parallel to the side of the crucible, and the insulation effect of the temperature field outside the short side of the crucible is less than the insulation effect of the temperature field outside the long side of the crucible.

[0014] Optionally, before heating the crucible until the gallium oxide raw material is melted into a melt, the method further includes: placing the crucible into a growth furnace, installing the temperature field of the growth furnace and then closing the furnace door; evacuating the growth furnace and then filling the growth furnace with protective gas to normal pressure.

[0015] The present invention provides an air inlet connected to an oxygen pipeline at the lower end at the middle position of the bottom of the crucible, and a heater and a flow valve are provided on the oxygen pipeline. During the crystal growth process, the flow valve is opened, and the temperature of the oxygen entering the oxygen pipeline is controlled by the heater to be lower than the temperature of the melt, and then the crucible is filled with oxygen whose temperature is lower than the temperature of the melt. At this time, the middle position of the crucible is affected by the oxygen bringing the cold source, which effectively reduces the temperature difference between the middle part of the crystal and the edge of the crystal, and avoids polycrystallization due to excessive temperature difference between the inside and outside of the crystal after the crystal size is too large. In addition, the oxygen entering the crucible will be fully mixed with the melt, and the reversible decomposition reaction of gallium oxide will tilt to the left, so that the gallium oxide melt will no longer decompose, the melt will no longer precipitate metal gallium, and the crucible will not be corroded by metal gallium. After the gallium oxide melt no longer decomposes, the volatilization of gallium oxide can also be effectively suppressed, and the temperature field temperature property is increased. Thus, the technical problem that the growth size of the crystal is affected by easy polycrystallization, easy volatilization of gallium oxide and easy corrosion of the crucible during the growth of gallium oxide crystals is effectively solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] A more complete understanding of exemplary embodiments of the present invention may be obtained by referring to the following drawings: Figure 1is a front view of an apparatus required for growing gallium oxide crystals according to an embodiment of the present invention; Figure 2 is a front cross-sectional view of an apparatus required for growing gallium oxide crystals according to an embodiment of the present invention; Figure 3 2 is a left side view of a device for growing gallium oxide crystals according to an embodiment of the present invention; Figure 4 is a left side cross-sectional view of an apparatus required for growing gallium oxide crystals according to an embodiment of the present invention; Figure 5 is a three-dimensional diagram of an apparatus required for growing gallium oxide crystals according to an embodiment of the present invention; Figure 6 is a top view of an apparatus required for growing gallium oxide crystals according to an embodiment of the present invention; Figure 7 It is a top cross-sectional view of an apparatus required for growing gallium oxide crystals according to an embodiment of the present invention. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be understood by people with general skills in the field to which the present invention belongs. "Including" and similar words used in this article mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0018] Combination Figures 1 to 7 As shown, an embodiment of the present invention provides a growth method for increasing the size of gallium oxide crystals, comprising the following steps: Step S1: Add gallium oxide raw material and dopant into crucible 7, and then heat crucible 7 until the gallium oxide raw material is melted into a melt; wherein, an air inlet 1 is pre-opened at the middle position of the bottom of crucible 7, an oxygen pipeline 4 is connected below the air inlet 1, and a first heater 5 and a flow valve 3 are arranged on the oxygen pipeline 4.

[0019] Step S2: Open the flow valve 3 and adjust the temperature of the oxygen entering the oxygen pipeline 4 to be lower than the temperature of the melt through the first heater 5, and the oxygen in the oxygen pipeline 4 enters the crucible 7 through the air inlet 1.

[0020] Step S3: gradually reducing the heating power of the crucible 7 at a first rate, and gradually reducing the flow rate of oxygen entering the crucible 7 at a second rate until the melt is exhausted; wherein the first rate is 30-60w / h, and the second rate is 4-6% / h.

[0021] Step S4: gradually reducing the heating power of the crucible 7 at a third rate, and ending the crystal growth after the crucible 7 is cooled to room temperature; wherein the third rate is 100-150w / h.

[0022] Specifically, an air inlet 1 with an oxygen pipeline 4 connected to its lower end may be pre-opened at the middle of the bottom of the crucible 7, and the oxygen pipeline 4 is provided with a first heater 5 and a flow valve 3. Then, the gallium oxide raw material and the dopant are added to the crucible 7, and then the crucible 7 is heated until the gallium oxide raw material is melted into a melt.

[0023] During the crystal growth process, the flow valve is opened, and the temperature of the oxygen entering the oxygen pipeline is controlled to be lower than the temperature of the melt by the first heater 5. In a specific embodiment, the temperature of the oxygen is controlled by the first heater 5 to be, for example but not limited to, 3-5°C lower than the melt temperature. Then, oxygen having a temperature lower than the melt temperature is filled into the crucible. After that, the heating power of the crucible 7 is gradually reduced at a first rate, and the flow rate of the oxygen entering the crucible 7 is gradually reduced at a second rate until the oxygen flow rate is reduced to 0 when the melt is completely crystallized. Among them, the first rate is 30-60w / h, and the second rate is 4-6% / h.

[0024] Therefore, during the crystal growth process, the middle position inside the crucible will be affected by the oxygen that brings the cold source, effectively reducing the temperature difference between the middle and edge of the crystal, and avoiding polycrystallization due to excessive temperature difference between the inside and outside of the crystal when the crystal size is too large. In addition, the oxygen entering the crucible will be fully mixed with the melt, and the reversible decomposition reaction of gallium oxide will tilt to the left, so that the gallium oxide melt will no longer decompose, the melt will no longer precipitate metallic gallium, and the crucible will not be corroded by metallic gallium. After the gallium oxide melt no longer decomposes, it can also effectively inhibit the volatilization of gallium oxide and increase the temperature field temperature. Therefore, it is conducive to the growth of larger gallium oxide crystals.

[0025] Among them, the reversible decomposition reaction formula of gallium oxide is as follows: Ga2O3⇌Ga2O+O2, 2Ga2O⇌4Ga+O2; In some embodiments of the present invention, before heating the crucible 7 until the gallium oxide raw material is melted into a melt, the crucible 7 is placed in a growth furnace (not shown in the figure), and the furnace door is closed after the temperature field 6 of the growth furnace is installed; the growth furnace is evacuated, and then a protective gas is filled into the growth furnace to normal pressure.

[0026] In some embodiments of the present invention, the gas inlet 1 is a multi-hole gas inlet. The design of the multi-hole gas inlet can reduce the impact of the oxygen gas flow entering the crucible 7 on the melt.

[0027] In some embodiments of the present invention, before heating the crucible 7 until the gallium oxide raw material is melted into a melt, a liquid sealing agent is added to the crucible 7 .

[0028] Specifically, the liquid sealing agent is, for example but not limited to, B2O3, which is used to adhere to the surface of the gallium oxide melt. Its function is not only to further reduce the volatilization of the gallium oxide melt, but also the liquid sealing agent between the crucible and the crystal can prevent the gallium oxide crystal from directly contacting the crucible 7. The liquid sealing agent is soluble in water, which is convenient for removing from the crucible. Otherwise, the gallium oxide crystal is severely adhered to the crucible 7 and cannot be taken out of the crucible.

[0029] In some embodiments of the present invention, a check valve (not shown in the figure) is further provided on the oxygen pipeline 4 and is located above the heater 5 and the flow valve 3. The design of the check valve can effectively prevent the melt from flowing into the oxygen pipeline when the oxygen flow rate is small.

[0030] In some embodiments of the present invention, the crucible 7 is in the shape of a parallelepiped.

[0031] Specifically, affected by the path dependence of the traditional crystal growth method, the current crucibles are all circumferentially symmetrical or axially symmetrical, and gallium oxide polycrystals are prone to occur when using existing crucibles for crystal growth. In order to solve this problem, the present invention has found through research that the gallium oxide unit cell pattern is similar to a parallelepiped, and the crucible shape is designed to be a parallelepiped. The crucible shape is designed according to the gallium oxide unit cell, which is more suitable for the anisotropy of gallium oxide crystals, avoids gallium oxide polycrystals, and is more conducive to growing larger crystals.

[0032] In some embodiments of the present invention, an anti-deformation coating is provided on the outside of the crucible 7. The anti-deformation coating can offset the pressure of the melt to prevent the crucible from deforming.

[0033] In some embodiments of the present invention, an anti-corrosion coating is provided on the inner side of the crucible 7. The anti-corrosion coating can further prevent the crucible from being corroded, and the crucible can hold more melt.

[0034] In addition, the traditional crucible has cracks caused by melt pressure and corrosion. The present invention can superimpose an anti-deformation coating and an anti-corrosion coating to enable the crucible to hold more melt without deformation, thereby growing larger crystals.

[0035] In some embodiments of the present invention, a temperature field 6 is arranged around the crucible 7, a second heater 2 for heating the crucible 7 is arranged outside the temperature field 6, and the temperature field outside the crucible 6 is arranged parallel to the side of the crucible 6, and the insulation effect of the temperature field outside the short side of the crucible 6 is less than the insulation effect of the temperature field outside the long side of the crucible 6.

[0036] Specifically, in this embodiment, considering that the thermal conductivity of gallium oxide in the 010 direction is good and the thermal conductivity in the 001 direction is poor, in order to maintain the temperature uniformity inside the crystal, it is necessary to weaken the heat preservation in the 001 direction (corresponding to the short side direction of the crucible) and strengthen the heat preservation in the 010 direction (corresponding to the long side direction of the crucible). Therefore, a temperature field 6 is arranged around the crucible 7, and the temperature field 6 includes a temperature field body 61 and a temperature field cover 62. A second heater 2 for heating the crucible 7 is arranged outside the temperature field 6, and the temperature field outside the crucible 6 is arranged parallel to the side of the crucible 6, and the heat preservation effect of the temperature field outside the short side of the crucible 6 is less than the heat preservation effect of the temperature field outside the long side of the crucible 6.

[0037] In addition, the shape of the temperature field is also designed as a parallelepiped according to the shape of the gallium oxide unit cell, which is more suitable for the temperature anisotropy of gallium oxide crystals and further avoids gallium oxide polycrystals.

[0038] In some embodiments of the present invention, after the crystal growth is finished, the crucible 7 is placed in an ultrasonic machine, and the ultrasonic and heating functions of the ultrasonic machine are turned on until the liquid sealing agent melts, and then the ultrasonic machine is turned off.

[0039] The size of the gallium oxide crystal grown by the conventional method is 2 inches, while the size of the gallium oxide crystal grown by the present method is 4 inches. In addition, the present method reduces the XRD half-peak width (full width at half maxima, referred to as FWHM, used to characterize the crystal quality) of the gallium oxide crystal from 200 arcsec to 40 arcsec.

[0040] In summary, the present invention opens an air inlet with an oxygen pipeline connected to the lower end at the middle position of the bottom of the crucible, and a heater and a flow valve are provided on the oxygen pipeline. During the crystal growth process, the flow valve is opened, and the temperature of the oxygen entering the oxygen pipeline is controlled by the heater to be lower than the temperature of the melt, and then the crucible is filled with oxygen with a temperature lower than the melt temperature. At this time, the middle position inside the crucible is affected by the oxygen brought by the cold source, which effectively reduces the temperature difference between the middle of the crystal and the edge of the crystal, and avoids the crystal size being too large and the temperature difference between the inside and outside being too large and polycrystallization. In addition, the oxygen entering the crucible will be fully mixed with the melt, and the reversible decomposition reaction of gallium oxide will tilt to the left, so that the gallium oxide melt will no longer decompose, the melt will no longer precipitate metal gallium, and the crucible will not be corroded by metal gallium. After the gallium oxide melt no longer decomposes, the volatilization of gallium oxide can also be effectively suppressed, and the temperature field temperature property is increased. Thus, the technical problem of affecting the crystal growth size due to easy polycrystallization, easy volatilization of gallium oxide and easy corrosion of crucible in the process of gallium oxide crystal growth is effectively solved.

[0041] The foregoing examples are merely illustrative and are used to explain some features of the method of the present invention. The appended claims are intended to claim the widest possible range that can be conceived, and the embodiments presented herein are only illustrations of selected implementations according to the combination of all possible embodiments. Therefore, it is the applicant's intention that the appended claims are not limited by the selection of examples that illustrate the features of the present invention. Some numerical ranges used in the claims also include sub-ranges within them, and changes in these ranges should also be interpreted as being covered by the appended claims where possible.

Claims

1. A method for increasing the size of gallium oxide crystals, characterized in that: include: Adding gallium oxide raw materials and dopants into a crucible, and then heating the crucible until the gallium oxide raw materials are melted into a melt; wherein an air inlet is pre-opened at the middle position of the bottom of the crucible, an oxygen pipeline is connected below the air inlet, and a first heater and a flow valve are arranged on the oxygen pipeline; Open the flow valve and adjust the temperature of the oxygen entering the oxygen pipeline to be lower than the temperature of the melt through the first heater, so that the oxygen in the oxygen pipeline enters the crucible through the air inlet; The heating power of the crucible is gradually reduced at a first rate, and the flow rate of oxygen entering the crucible is gradually reduced at a second rate until the melt is exhausted; wherein the first rate is 30-60w / h, and the second rate is 4-6% / h; The heating power of the crucible is gradually reduced at a third rate, and the crystal growth is terminated after the crucible is cooled to room temperature; wherein the third rate is 100-150w / h.

2. The method according to claim 1, characterized in that The air inlet is a multi-hole air inlet.

3. The method according to claim 1, characterized in that: Before heating the crucible until the gallium oxide raw material is melted into a melt, the method further includes: adding a liquid sealing agent into the crucible.

4. The method according to claim 3, characterized in that Also includes: After the crystal growth is finished, the crucible is placed in an ultrasonic machine, and the ultrasonic and heating functions of the ultrasonic machine are turned on until the liquid sealing agent melts, and then the ultrasonic machine is turned off.

5. The method according to claim 1, characterized in that: The oxygen pipeline is also provided with a check valve located above the heater and the flow valve.

6. The method according to claim 1, characterized in that The crucible is in the shape of a parallelepiped.

7. The method according to claim 1, characterized in that The outer side of the crucible is provided with an anti-deformation coating.

8. The method according to claim 1, characterized in that: The inner side of the crucible is provided with an anti-corrosion coating.

9. The method according to claim 1, characterized in that: A temperature field is arranged around the crucible, a second heater for heating the crucible is arranged outside the temperature field, and the temperature field outside the crucible is arranged parallel to the side of the crucible, and the insulation effect of the temperature field outside the short side of the crucible is smaller than the insulation effect of the temperature field outside the long side of the crucible.

10. The method according to claim 1, characterized in that Before heating the crucible until the gallium oxide raw material is melted into a melt, the method further comprises: Putting the crucible into a growth furnace, installing the temperature field of the growth furnace and closing the furnace door; The growth furnace is evacuated, and then a protective gas is filled into the growth furnace to normal pressure.

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