Method, system and detection method for growing gallium nitride single crystal by flux method

Abstract

The present invention discloses a method, system, and detection method for growing gallium nitride single crystals using a flux method. The method comprises: applying a voltage to a molten growth material during liquid phase epitaxial growth of a gallium nitride single crystal using a flux method to at least cause the molten growth material to flow and / or reduce the surface energy of the molten growth material. An embodiment of the present invention provides a method for growing uniform gallium nitride single crystals using a voltage-induced flux method. The method uses a voltage to cause the molten growth material within the growth system to flow, thereby enabling more thorough and uniform mixing of the material, thereby growing a gallium nitride bulk single crystal of more uniform quality.

Description

Technical Field

[0001] The present invention relates to a method for growing gallium nitride single crystals using a flux method, and in particular to a method, system and detection method for growing gallium nitride single crystals using a flux method, belonging to the fields of electronic science and technology, and semiconductor materials and device technology. Background Art

[0002] As one of the core materials of third-generation semiconductors, gallium nitride (GaN) possesses excellent properties such as a wide bandgap, high electron mobility, high breakdown field strength, high thermal conductivity, low dielectric constant, strong radiation resistance, and good chemical stability. GaN is widely used in optical devices and high-power electronic devices, such as light-emitting diodes (LEDs), laser diodes (LDs), and high-power transistors. Currently, there are four main methods for producing GaN single crystal substrates, including the high-pressure melt method, the hydride vapor phase epitaxy method, the ammonothermal method, and the flux method. The flux method, as a growth method near thermodynamic equilibrium, has many advantages and is currently one of the internationally recognized methods for obtaining low-cost, high-quality, large-sized GaN bulk single crystals.

[0003] The general growth process of GaN bulk single crystals using the flux method is as follows: select appropriate raw material composition ratios (mainly metallic gallium, metallic sodium, carbon additives, etc.), place the crucible containing the growth materials and GaN seed crystals in a growth furnace, and then, in a nitrogen atmosphere at a certain growth temperature and pressure, grow GaN bulk single crystals of varying thicknesses by liquid phase epitaxy on the GaN seed crystals by controlling the growth time.

[0004] However, during the gallium nitride growth process, due to the poor fluidity and high surface tension of the molten gallium nitride growth raw materials (mainly metallic gallium and metallic sodium), the substrate and the molten metal form a large wetting angle θ, which reduces the wettability of the molten metal, that is, the degree of dispersion of the molten liquid metal on the substrate, making the distribution of the molten metal liquid uneven, resulting in uneven thickness and quality of the grown gallium nitride, and easily incorporating more impurities, reducing the quality of crystal growth. Summary of the Invention

[0005] The main purpose of the present invention is to provide a method, system and detection method for growing gallium nitride single crystals using a flux method to overcome the shortcomings of the existing technology.

[0006] To achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include:

[0007] An embodiment of the present invention provides a method for growing a gallium nitride single crystal using a voltage-induced flux method, comprising: when growing a gallium nitride single crystal by liquid phase epitaxy using a flux method, applying a voltage to a molten growth material therein to at least drive the molten growth material to flow and / or reduce the surface energy of the molten growth material.

[0008] Furthermore, the method includes: adjusting one or more of the flow speed, flow direction, and flow frequency of the molten growth material by at least regulating one or more of the magnitude, direction, and frequency of the voltage applied to the molten growth material.

[0009] Furthermore, the method includes: applying a voltage including a pulse voltage, a sinusoidal voltage or a cosine voltage to the molten growth material to drive the molten growth material to flow back and forth.

[0010] Furthermore, the method includes: applying voltage to the molten growth material to keep the gallium nitride single crystal growth conditions therein in a balanced state.

[0011] Furthermore, the method includes: applying a voltage of -220 to 220V to the molten growth material.

[0012] Furthermore, the mass ratio of Ga to Na in the molten growth raw material is 10:0 to 1:10.

[0013] Furthermore, the Na in the molten growth raw material serves as a metal flux, and the metal flux can be an alkali metal or alkaline earth metal flux, or a composite flux of two or more alkali metals or alkaline earth metal fluxes, such as a composite flux of sodium (Na) metal and strontium (Sr) metal.

[0014] Furthermore, the method includes: the mass ratio of Ga to Na in the molten growth material is 1:1-1:10, particularly preferably 3:7, and the voltage applied to the molten growth material is -36 to 36V accordingly.

[0015] An embodiment of the present invention further provides a method for detecting the liquid phase epitaxial growth state of a gallium nitride single crystal, comprising: growing a gallium nitride single crystal using the method described, and detecting changes in current in a molten growth material during the growth process, thereby detecting the growth state of the gallium nitride single crystal therein.

[0016] An embodiment of the present invention further provides a system for growing gallium nitride single crystals using a voltage-induced flux method, comprising:

[0017] A growth unit for uniform liquid phase epitaxial growth of gallium nitride single crystals by a flux method;

[0018] And, the system further comprises:

[0019] The voltage applying unit is used to apply voltage to the molten growth material in the gallium nitride single crystal liquid phase epitaxial growth system to at least drive the molten growth material to flow and / or reduce the surface energy of the molten growth material.

[0020] Furthermore, the parameters of the voltage applied by the voltage applying unit to the molten growth material are adjustable, and the parameters include one or more of the magnitude, direction, and frequency of the voltage.

[0021] Furthermore, the voltage applied by the voltage applying unit to the molten growth material can keep the gallium nitride single crystal growth conditions therein in a balanced state.

[0022] Furthermore, the system further comprises:

[0023] The current detection module is used to detect the current change in the molten growth material.

[0024] An embodiment of the present invention also provides a method for growing semiconductor compound single crystals based on a voltage-induced flux method, which includes: when growing semiconductor compound single crystals by liquid phase epitaxy using a flux method, applying voltage to the molten growth material therein to at least drive the molten growth material to flow and / or reduce the surface energy of the molten growth material.

[0025] Furthermore, the semiconductor compound includes gallium nitride and aluminum nitride.

[0026] Compared with the prior art, the advantages of the present invention include:

[0027] 1) The present invention provides a method for growing uniform gallium nitride single crystals using a voltage-induced flux method. This method uses voltage to drive the flow of molten growth materials within the growth system, enabling more thorough and uniform mixing of the materials, thereby growing gallium nitride bulk single crystals with more uniform quality.

[0028] 2) The present invention provides a method for growing uniform gallium nitride single crystals using a voltage-induced flux method, which can remove impurities from the molten growth material, thereby preventing excessive impurities from being incorporated into the molten growth material, thereby further improving the growth quality of the gallium nitride crystals.

[0029] 3) The present invention provides a method for growing uniform gallium nitride single crystals using a voltage-induced flux method. By regulating the magnitude, direction, and frequency of the applied voltage, the fluidity of the molten growth material can be controlled, allowing the growth system to maintain a growth equilibrium state for a long period of time. This avoids the problem of disordered crystallization during gallium nitride growth and reduces the probability of growing gallium nitride polycrystals, thereby obtaining high-quality gallium nitride single crystals.

[0030] 4) The system structure for growing uniform gallium nitride single crystals using a voltage-induced flux method provided by the embodiment of the present invention is simple and easy to modify. This can be achieved by adding a voltage-induced unit to the existing gallium nitride single crystal epitaxial equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic structural diagram of a system for growing uniform gallium nitride single crystals based on a voltage-induced flux method provided in a typical embodiment of the present invention;

[0032] Figure 2 is the distribution state of the molten growth material when no voltage is applied;

[0033] Figure 3 It is the distribution state of the molten growth material when a preset voltage is applied;

[0034] Figure 4-Figure 8 These are electron microscope images of the gallium nitride single crystals grown in Examples 1-5 of the present invention;

[0035] Figure 9-10 They are electron microscope images of the gallium nitride single crystals grown in comparative examples 1-2 respectively. DETAILED DESCRIPTION

[0036] In view of the shortcomings of the prior art, the inventors of this case, after long-term research and extensive practice, have proposed the technical solution of the present invention. The following will further explain this technical solution, its implementation process and principles.

[0037] The explanations of some technical terms involved in this manual are as follows:

[0038] Wetting angle θ: The angle between the liquid-solid interface and the tangent line of the liquid surface at the contact point between the liquid and solid phases. An angle less than 90° indicates wetting, and an angle greater than 90° indicates non-wetting.

[0039] The flux method, also known as the molten salt method, is a method of artificially producing single crystals from a melt using a flux. The material is melted by the flux in the crucible when it is below its melting point, allowing the crystallization process to proceed under normal pressure, which is its greatest advantage. Because this method requires a relatively high growth temperature, it is generally referred to as the high-temperature solution growth method. The original components of the crystal are dissolved in a low-melting-point flux solution at high temperature to form a uniform saturated solution. The solution is then slowly cooled or other methods are used to form a supersaturated solution, allowing the crystals to precipitate.

[0040] Surface energy: The non-volume work required to reversibly increase the surface area of ​​a system under constant temperature, constant pressure, and constant composition. Another definition of surface energy is the excess energy of surface particles relative to internal particles.

[0041] It should be noted that the gallium nitride seed crystal is a homogeneous substrate, which can be a gallium nitride self-supporting substrate or a composite substrate, that is, a gallium nitride epitaxial film grown on a heterogeneous substrate, which can be one or more of but not limited to sapphire, silicon, SiC or diamond materials using growth methods such as MOCVD, MBE, HVPE; or a heterogeneous substrate, such as one or more of but not limited to sapphire, silicon, SiC or diamond materials, can be used to epitaxially grow a single piece of GaN thick film material or multiple pieces of GaN thick film materials can be grown simultaneously in a high-pressure reactor to obtain a single piece or multiple pieces of GaN single crystal substrate.

[0042] The inventors of this case have found that due to the high conductivity of liquid gallium, it has been observed that the electric field can promote the movement of molten gallium on pure gallium (99.99%, melting point 29.8°C), and the applied electric field can also change its surface tension. The distribution state of the molten growth material when no voltage is applied is as follows: Figure 2 As shown, the distribution state of the molten growth material when the preset voltage is applied is as follows Figure 3 shown.

[0043] Specifically, the inventors of this case added a voltage-inducing unit to the existing liquid-phase epitaxial growth system of gallium nitride single crystals. During the liquid-phase epitaxial growth of gallium nitride single crystals using a flux method, a preset voltage was applied to the molten growth material in the gallium nitride single crystal growth system to reduce the surface tension of the molten metal and the wetting angle θ between the substrate and the molten metal, thereby uniformly distributing the molten growth material. In addition, applying a preset voltage to the molten growth material can promote the movement of the molten metal in the molten growth material, thereby improving the fluidity of the molten growth material, so that the gallium nitride single crystals epitaxially grown in the embodiment of the present invention have uniform thickness, better uniformity, and higher crystal quality.

[0044] An embodiment of the present invention also provides a method for growing uniform gallium nitride single crystals using a voltage-induced flux method. During the liquid phase epitaxial growth of the gallium nitride single crystal using the flux method, a voltage of -220-220 V and a frequency of 0.001-50 Hz are applied to the molten growth material in the gallium nitride single crystal growth system. By changing the magnitude, direction, and frequency (alternating current) of the voltage, the molten growth material is given better fluidity. Specifically, pulse voltage, sine / cosine voltage, or the like can be applied to cause the molten growth material to achieve reciprocating motion, thereby improving the fluidity of the molten growth material. The application of voltage further reduces the surface energy of the molten growth material, thereby improving the uniformity of the molten growth material and achieving uniform liquid phase epitaxial growth of the gallium nitride single crystal.

[0045] Specifically, an embodiment of the present invention further provides a method for growing uniform gallium nitride single crystals based on a voltage-induced flux method, in which the applied voltage varies with the Ga-Na ratio in the molten growth raw material, wherein the mass ratio of Ga-Na in the molten growth raw material is 10:0 to 1:10, preferably 1:1 to 1:10, and particularly preferably 3:7, and the applied voltage is preferably -36 to 36V.

[0046] Specifically, when a preset voltage is applied to the molten growth material, a current will be generated in the molten growth material. By using an ammeter to detect the change in the current in the molten growth material, the state of the gallium nitride single crystal growth process can be monitored, such as crystal morphology, growth thickness and other parameters.

[0047] Specifically, the method for growing uniform gallium nitride single crystals using a voltage-induced flux method provided by an embodiment of the present invention is based on at least one principle: as the molten raw material is consumed, its conductivity changes. Based on the current magnitude and rate of change, the growth rate and the real-time yield of the gallium nitride single crystal can be simply determined. For example, when the current decreases and the rate of change increases, the real-time yield of the gallium nitride single crystal is determined to be increasing; conversely, it is determined to be decreasing. The technical solution, its implementation process, and principles will be further explained below with reference to the accompanying drawings and specific implementation examples. Unless otherwise specified, the gallium nitride single crystal growth materials and testing methods used in the embodiments of the present invention are known to those skilled in the art.

[0048] See also Figure 1 An embodiment of the present invention provides a system for growing uniform gallium nitride single crystals using a voltage-induced flux method, comprising: a single crystal growth unit and a voltage-inducing unit, wherein the single crystal growth unit includes a reaction chamber for reactively growing nitride single crystals, and the voltage-inducing unit is at least used to apply voltage to the molten growth material in the reaction chamber. The single crystal growth unit may be known to those skilled in the art and is not specifically limited herein. The voltage-inducing unit may include a power supply and two electrodes or metal conductors.

[0049] Specifically, a method for growing uniform gallium nitride single crystals based on a voltage-induced flux method may include:

[0050] Provide Figure 1 The system shown;

[0051] In an anhydrous and oxygen-free environment, metallic gallium and metallic sodium are mixed in a mass ratio of 10:0-1:10 to form a molten metal, with the amount of Ga being greater than 0. A carbon additive and a gallium nitride seed crystal are then added to form a gallium nitride single crystal growth system.

[0052] The gallium nitride single crystal growth system is transferred to an epitaxial growth device, a voltage of -220-220 V is applied to the molten metal in the gallium nitride single crystal growth system, and liquid phase epitaxial growth of the gallium nitride single crystal is performed under the conditions of a pressure of 3-10 MPa and a temperature of 700-1000°C.

[0053] Example 1

[0054] In a water- and oxygen-free glove box, metallic gallium and metallic sodium are mixed in a crucible at a mass ratio of 1:1, and then a carbon additive (5% of the total amount of metallic sodium and gallium) is added. Then, a gallium nitride seed crystal is added to form a gallium nitride single crystal growth system.

[0055] The growth system is transferred to an epitaxial growth device, and liquid phase epitaxial growth of a gallium nitride single crystal using a flux method is carried out at a pressure of 3-5 MPa and a temperature of 700-1000°C. At the same time, forward and reverse voltages are applied to the molten growth material, and the applied voltage is -220 V and the frequency is 0.001 Hz.

[0056] Example 2

[0057] In a water- and oxygen-free glove box, metallic gallium and metallic sodium were mixed in a crucible at a mass ratio of 27:73, and then a carbon additive (0.5% of the total amount of metallic sodium and gallium) was added. Then, a gallium nitride seed crystal was added to form a gallium nitride single crystal growth system.

[0058] The growth system is transferred to an epitaxial growth device, and liquid phase epitaxial growth of a gallium nitride single crystal using a flux method is carried out at a pressure of 3-5 MPa and a temperature of 700-1000°C. At the same time, forward and reverse voltages are applied to the molten growth material, and the applied voltage is -36 V and the frequency is 1 Hz.

[0059] Example 3

[0060] In a water- and oxygen-free glove box, metallic gallium and metallic sodium are mixed in a crucible at a mass ratio of 1:10, and then a carbon additive (0.5% of the total amount of metallic sodium and gallium) is added. Then, a gallium nitride seed crystal is added to form a gallium nitride single crystal growth system.

[0061] The growth system is transferred to an epitaxial growth device, and liquid phase epitaxial growth of a gallium nitride single crystal using a flux method is carried out at a pressure of 3-5 MPa and a temperature of 700-1000°C. At the same time, forward and reverse voltages of 18 V and 10 Hz are applied to the molten growth material.

[0062] Example 4

[0063] In a water- and oxygen-free glove box, metallic gallium and metallic sodium were mixed in a crucible at a mass ratio of 27:73, and then a carbon additive (0.5% of the total amount of metallic sodium and gallium) was added. Then, a gallium nitride seed crystal was added to form a gallium nitride single crystal growth system.

[0064] The growth system was transferred to an epitaxial growth device, and liquid phase epitaxial growth of a gallium nitride single crystal using a flux method was carried out at a pressure of 3-5 MPa and a temperature of 700-1000°C. At the same time, forward and reverse voltages of 36 V and 50 Hz were applied to the molten growth material.

[0065] Example 5

[0066] In a water- and oxygen-free glove box, metallic gallium and metallic sodium were mixed in a crucible at a mass ratio of 73:27. A carbon additive (0.5% of the total amount of metallic sodium and gallium) was then added, followed by a gallium nitride seed crystal, thereby forming a gallium nitride single crystal growth system.

[0067] The growth system is transferred to an epitaxial growth device, and liquid phase epitaxial growth of a gallium nitride single crystal using a flux method is carried out at a pressure of 3-5 MPa and a temperature of 700-1000°C. At the same time, forward and reverse voltages of 220 V and 35 Hz are applied to the molten growth material.

[0068] Comparative Example 1

[0069] In a water- and oxygen-free glove box, metallic gallium and metallic sodium were mixed in a crucible at a mass ratio of 27:73, and then a carbon additive (0.5% of the total amount of metallic sodium and gallium) was added. Then, a gallium nitride seed crystal was added to form a gallium nitride single crystal growth system.

[0070] The growth system is transferred to an epitaxial growth device, and liquid phase epitaxial growth of a gallium nitride single crystal using a flux method is performed under the conditions of a pressure of 3-5 MPa and a temperature of 700-1000° C.

[0071] Comparative Example 2

[0072] In a water- and oxygen-free glove box, metallic gallium and metallic sodium were mixed in a crucible at a mass ratio of 27:73, and then a carbon additive (0.5% of the total amount of metallic sodium and gallium) was added. Then, a gallium nitride seed crystal was added to form a gallium nitride single crystal growth system.

[0073] The growth system is transferred to an epitaxial growth device, the molten growth material in the growth system is stirred, and liquid phase epitaxial growth of a gallium nitride single crystal using a flux method is performed under conditions of a pressure of 3-5 MPa and a temperature of 700-1000° C.

[0074] The electron microscope images of the gallium nitride single crystals grown in Examples 1-5 and Comparative Examples 1-2 are shown in Figures 1-2 and 1-3. Figure 4-Figure 8 、 Figure 9-10 As shown in the figure, it can be seen that the gallium nitride single crystals obtained in Example 2 and Example 4 have the best uniformity, morphology and other qualities, followed by Example 1, 3 and 5, and Comparative Example 2 is the third, and Comparative Example 1 is the worst.

[0075] Embodiments of the present invention provide a method for growing uniform gallium nitride single crystals using a voltage-induced flux method. Voltage is used to drive the flow of molten growth feedstock within a growth system. Because molten metal is a good conductor and molten gallium metal can move under the action of voltage, uniformity of the molten growth feedstock can be achieved by simply applying a certain voltage to the molten growth feedstock. This improves the fluidity of the molten growth feedstock, allowing the feedstock to be more thoroughly and evenly mixed, thereby growing gallium nitride bulk single crystals with more uniform quality. Furthermore, the high fluidity can remove impurities from the molten growth feedstock, thereby preventing excessive impurities from being incorporated into the molten growth feedstock, further improving the growth quality of the gallium nitride crystals.

[0076] An embodiment of the present invention provides a method for growing uniform gallium nitride single crystals based on a voltage-induced flux method. The fluidity of the molten growth material can be controlled by regulating the magnitude, direction, and frequency of the applied voltage, so that the growth system can remain in a growth equilibrium state for a long time, thereby avoiding the problem of disordered crystallization during the gallium nitride growth process and reducing the probability of growing gallium nitride polycrystals, thereby obtaining gallium nitride single crystals with higher growth quality.

[0077] In addition, the embodiment of the present invention provides a system for growing uniform gallium nitride single crystals based on a voltage-induced flux method. The system has a simple structure and is easy to modify. This can be achieved by adding a voltage-inducing unit to the existing gallium nitride single crystal epitaxial equipment.

[0078] It should be understood that the above embodiments are merely illustrative of the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent variations or modifications made in accordance with the spirit and substance of the present invention are intended to be encompassed within the scope of protection of the present invention.

Claims

1. A method for growing gallium nitride single crystals based on a voltage-induced flux method, characterized in that include: When growing a gallium nitride single crystal by liquid phase epitaxy using a flux method, a voltage is applied to the molten growth material therein to at least drive the molten growth material to flow and / or reduce the surface energy of the molten growth material. In addition, by at least regulating one or more of the magnitude, direction, and frequency of the voltage applied to the molten growth material, one or more of the flow velocity, flow direction, and flow frequency of the molten growth material is adjusted, so that the growth system is in an equilibrium state for growing the gallium nitride single crystal.

2. The method according to claim 1, characterized in that include: The voltage applied to the molten growth material includes a pulse voltage, a sinusoidal voltage, or a cosine voltage to drive the molten growth material to flow back and forth.

3. The method according to any one of claims 1 to 2, characterized in that include: By applying voltage to the molten growth material, the gallium nitride single crystal growth conditions therein are kept in a balanced state.

4. The method according to claim 1, wherein: The voltage applied to the molten growth material is -220V to 220V.

5. The method according to claim 1 or 4, wherein: The mass ratio of Ga to Na in the molten growth raw material is 1:1-1:

10.

6. The method according to claim 5, wherein include: The ratio of Ga to Na in the molten growth material is 1:1-1:10, and the voltage applied to the molten growth material is -36~36V accordingly.

7. A method for detecting the growth state of gallium nitride single crystal liquid phase epitaxial growth, characterized in that include: A gallium nitride single crystal is grown by the method according to any one of claims 1 to 6, and changes in the current in the molten growth material are detected during the growth process, thereby realizing detection of the growth state of the gallium nitride single crystal therein.

8. A system for growing gallium nitride single crystals using a voltage-induced flux method, comprising: A growth unit for uniform liquid phase epitaxial growth of gallium nitride single crystals by a flux method; Characterized in that the system further comprises: A voltage applying unit is used to apply a voltage to a molten growth material in a gallium nitride single crystal liquid phase epitaxial growth system to at least drive the molten growth material to flow and / or reduce the surface energy of the molten growth material. The parameters of the voltage applied by the voltage applying unit to the molten growth material are adjustable, and the parameters include one or more of the magnitude, direction, and frequency of the voltage.

9. The system according to claim 8, characterized in that: The voltage applied by the voltage applying unit to the molten growth material can keep the gallium nitride single crystal growth conditions therein in a balanced state.

10. The system according to claim 8, characterized in that Also includes: The current detection module is used to detect the current change in the molten growth material.

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