Method for preparing gallium nitride nanowire array by flux method

Abstract

The invention discloses a method for preparing a gallium nitride nanowire array by a flux method. The method comprises the following steps: providing a liquid phase system of an alloy catalytic material containing Ga and a transition metal element with a catalytic property, and a Ga-Na liquid phase alloy; under the condition of isolating water and oxygen, enabling the liquid phase system to be in contact with the gallium nitride single crystal substrate, under the atmosphere of high-pressure nitrogen, enabling the metal sodium to dissociate nitrogen at high temperature, and realizing c-direction growth of the gallium nitride nanowire array on the gallium nitride single crystal substrate under the catalytic action of the alloy catalytic material. The preparation of the raw materials only needs to be completed at one time, the substrate does not need to be specially treated, only gallium, sodium, nickel and nitrogen are used as the raw materials, and the cost is low; compared with a traditional sodium fluxing agent method for growing gallium nitride single crystals, the method has the advantages that a sodium-gallium-transition metal melt liquid-phase system with the catalytic property of the sodium fluxing agent is utilized, and the high-density gallium nitride nanowire is innovatively prepared.

Description

Technical Field

[0001] The invention relates to a method for preparing a gallium nitride nanowire array, in particular to a method for preparing a gallium nitride nanowire array using a flux method, and belongs to the technical field of gallium nitride nanomaterial preparation. Background Art

[0002] GaN's wide direct bandgap, high electron saturation drift velocity, high electron mobility, good thermal conductivity, strong chemical stability, and radiation resistance make it an ideal material for optoelectronic applications. Compared with bulk GaN materials, GaN nanowires have a higher specific surface area, providing a higher light absorption area and higher photoelectric conversion efficiency.

[0003] At present, the preparation of GaN nanowires is mainly divided into two ways: "top-down" and "bottom-up". Among them, "top-down" is to obtain nanowire microstructures by etching or corrosion. Due to the strong chemical stability of GaN, its processing is difficult; "bottom-up" is a method of directly growing nanowire structures. At present, it is basically prepared by gas phase method, including chemical vapor deposition, hydride vapor deposition, metal-oxide vapor deposition and molecular beam epitaxy. However, the gas phase method generally requires catalytic deposition or growth template preparation, which increases the preparation cost of nanowire growth and prolongs the preparation cycle.

[0004] For example, the existing patent CN103387213A discloses a gallium nitride nanowire and a preparation method thereof, wherein a single substance of gallium, gallium oxide and a gas containing ammonia are chemically vapor deposited on a substrate loaded with a catalyst for preparing gallium nitride nanowires under normal pressure to prepare gallium nitride nanowires having a periodic structure. The preparation process of this method requires the use of ammonia, which is environmentally harmful, and a metal catalyst is used in the preparation process. After the preparation is completed, alloy residues are present at the ends of the nanowires, which are difficult to remove. AOKI M, YAMANE H, SHIMADA M, et al. Influence of 3d-Transition-Metal Additives on Single Crystal Growth of GaN by the Na Flux Method [J]. Japanese Journal of Applied Physics, 2003, 42: 5445-9. A method using sodium flux is disclosed, which can achieve the growth of gallium nitride crystals at a temperature of 750-850°C and a nitrogen pressure of 5MPa. Adding transition metal elements to the melt significantly improves the growth characteristics of gallium nitride, wherein nickel metal significantly increases the c-direction growth rate of gallium nitride. However, this method directly adds transition metals to the melt, and the grown gallium nitride is generated by spontaneous nucleation, which belongs to the category of bulk single crystals and does not present a nanostructure. Also, the existing patent CN115369379A discloses a method for preparing GaN nanowires and GaN nanowires, wherein the preparation method includes: preparing a two-dimensional material layer on a substrate to obtain a composite growth template; preparing a metal film layer on the two-dimensional material layer of the composite growth template; placing the composite growth template with the metal film layer in a growth device to grow GaN nanowires. In this method, the preparation of nanowires relies on a heterogeneous substrate and a two-dimensional material on the substrate surface, which has a lattice mismatch and thermal mismatch with gallium nitride itself, and a metal catalyst is used at the same time. After the preparation is completed, there is alloy residue at the end of the nanowire, which is not easy to remove. Summary of the invention

[0005] The main purpose of the present invention is to provide a method for preparing gallium nitride nanowire arrays by a flux method, thereby overcoming the shortcomings of the prior art.

[0006] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes:

[0007] An embodiment of the present invention provides a method for preparing a gallium nitride nanowire array by a flux method, which comprises:

[0008] Providing a liquid phase system comprising an alloy catalytic material of Ga and a transition metal element having catalytic properties, and a Ga-Na liquid phase alloy;

[0009] Under the condition of isolating water and oxygen, the liquid phase system is brought into contact with a gallium nitride single crystal substrate, and in a high-pressure nitrogen atmosphere, metallic sodium dissociates nitrogen at a high temperature, and a gallium nitride nanowire array is grown in the c direction of the gallium nitride single crystal substrate under the catalytic action of the alloy catalytic material.

[0010] In some embodiments, the alloy catalytic material is dispersed in a Ga—Na liquid phase alloy, wherein a portion of the alloy catalytic material is in contact with a gallium nitride single crystal substrate, thereby achieving catalytic growth of a gallium nitride nanowire array at the interface between the alloy catalytic material and the gallium nitride single crystal substrate.

[0011] The embodiment of the present invention also provides a gallium nitride nanowire array prepared by the above method.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] 1) The method for preparing gallium nitride nanowire arrays by flux method provided by the present invention only needs to prepare raw materials once, and no special treatment of the substrate is required. The raw materials only use metal gallium, sodium, nickel and nitrogen, and the cost is low. Nitrogen is used instead of ammonia that is harmful to the environment, which is more environmentally friendly.

[0014] 2) Compared with the traditional sodium flux method for growing GaN bulk single crystals, the present invention utilizes the sodium flux of the sodium-gallium-transition metal melt liquid phase system with catalytic properties to innovatively prepare high-density GaN nanowires. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 is a schematic diagram of the principle of preparing a gallium nitride nanowire array in a gallium-sodium-nickel melt in a typical embodiment of the present invention;

[0017] Figure 2 is a process flow chart for preparing a gallium nitride nanowire array in a typical embodiment of the present invention;

[0018] Figure 3 is a schematic diagram of the growth principle of a gallium nitride nanowire array in a typical embodiment of the present invention;

[0019] Figure 4 It is the Ga-Na binary phase diagram;

[0020] Figure 5It is the Ga-Ni binary phase diagram;

[0021] Figure 6 This is a low-magnification image of the surface morphology of the gallium nitride nanowire prepared in Example 1 of the present invention;

[0022] Figure 7 is a high-magnification image of the surface morphology of the gallium nitride nanowire prepared in Example 1 of the present invention;

[0023] Figure 8 This is a bird's-eye view of the gallium nitride nanowires prepared in Example 1 of the present invention tilted at 45°;

[0024] Fig. 9 This is a statistical diagram of the radius of the gallium nitride nanowires prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0025] In view of the problems of the prior art, the inventors of this case have proposed the technical solution of the present invention after long-term research and extensive practice. Growing gallium nitride by the flux method is a common growth method for gallium nitride bulk single crystals. The use of sodium-gallium alloy significantly reduces the growth pressure of gallium nitride and increases the concentration of nitrogen in the melt, thereby achieving the growth of gallium nitride crystals. Adding suitable additives can significantly affect the growth mode of gallium nitride crystals in the melt. The inventors of this case unexpectedly discovered that adding a certain proportion of transition metals with catalytic properties to the sodium-gallium melt can achieve the preparation of gallium nitride nanowire arrays on a gallium nitride homogeneous substrate.

[0026] The technical solution, its implementation process and principle will be further explained as follows.

[0027] As one aspect of the technical solution of the present invention, a method for preparing a gallium nitride nanowire array by a flux method includes:

[0028] Providing a liquid phase system comprising an alloy catalytic material of Ga and a transition metal element having catalytic properties, and a Ga-Na liquid phase alloy;

[0029] Under the condition of isolating water and oxygen, the liquid phase system is brought into contact with a gallium nitride single crystal substrate, and in a high-pressure nitrogen atmosphere, metallic sodium dissociates nitrogen at a high temperature, and a gallium nitride nanowire array is grown in the c direction of the gallium nitride single crystal substrate under the catalytic action of the alloy catalytic material.

[0030] The method of the present invention is an improvement based on the sodium flux method. The traditional sodium flux method is a method for growing gallium nitride bulk single crystals. The growth ingredients generally require Ga and Na to be matched in a certain ratio. Currently, there is no relevant report on the preparation of nanowires in a liquid phase system such as sodium flux. When studying the sodium flux method for growing gallium nitride bulk single crystals, the present invention accidentally achieves the preparation of gallium nitride nanowire arrays.

[0031] In some embodiments, the transition metal element having catalytic properties may include at least any one of Fe, Co, Ni, etc., but is not limited thereto.

[0032] In some embodiments, the alloy catalytic material is dispersed in a Ga-Na liquid phase alloy, wherein a portion of the alloy catalytic material is in contact with a gallium nitride single crystal substrate, thereby achieving catalytic growth of a gallium nitride nanowire array at the interface between the alloy catalytic material and the gallium nitride single crystal substrate.

[0033] In some embodiments, the mass ratio of Ga to the transition metal element with catalytic properties in the alloy catalyst material is 83:17 to 98:2. The inventors of this case have found through multiple experiments that too high a Ni ratio may cause the Ni2Ga3 particles to be too large in diameter or densely distributed, resulting in a larger diameter of the grown GaN nanowires or merging and growing into a non-nanowire structure; too low a Ni ratio may cause the diameter of the Ni2Ga3 particles in the liquid phase to be too small, failing to meet the conditions for catalytic growth.

[0034] In some embodiments, the mass ratio of the sum of Ga and the transition metal element with catalytic properties to Na in the liquid phase system is 25:75 to 33:67.

[0035] In some embodiments, the method includes: mixing a transition metal with catalytic properties with liquid metal Ga in an inert atmosphere, and mixing them at 800-950° C. for 20-25 hours to achieve sufficient mixing, thereby prefabricating the alloy catalytic material.

[0036] In some embodiments, the alloy catalytic material includes alloy catalytic particles having a diameter of about 800 to 250 nm.

[0037] In some embodiments, the method comprises:

[0038] In a water and oxygen removal device, Ga is prepared with a transition metal having catalytic properties to form an alloy catalytic material;

[0039] And, the alloy catalyst material is mixed with Ga and Na to form a liquid phase system.

[0040] In some embodiments, the method comprises: placing the liquid phase system in a reaction device having a gallium nitride single crystal substrate at the bottom, and transferring the liquid phase system to a high-pressure reaction chamber in a device isolating water and oxygen.

[0041] In some more preferred embodiments, the method further comprises: repeatedly inputting and extracting nitrogen into the high-pressure reaction chamber, thereby removing water and oxygen in the high-pressure reaction chamber.

[0042] In some embodiments, the pressure of the high-pressure nitrogen atmosphere is 2-4 MPa. The present invention does not need to use ammonia, but uses environmentally friendly nitrogen as a nitrogen source, which is more environmentally friendly, and the growth system has a self-cleaning effect, and the surface of the nanowires is cleaner.

[0043] In some embodiments, the method includes: during the growth process, first heating to 630-660° C. and maintaining for 1-2 hours to provide nucleation points on the substrate, and then heating to 800-830° C. and growing for 10-15 hours.

[0044] Furthermore, the present invention adopts a homogeneous gallium nitride substrate to avoid the lattice mismatch and thermal mismatch of the material itself, and the growth system has a self-cleaning effect, so the surface of the nanowire is cleaner.

[0045] In some more preferred embodiments, the method further comprises: after the growth is completed, cleaning the alloy catalyst material on the top of the gallium nitride nanowire array with a cleaning agent. The method of the present invention uses simple equipment and simple process, and the catalyst residue can be removed by simple cleaning.

[0046] Furthermore, the cleaning agent includes but is not limited to anhydrous ethanol.

[0047] Among them, in some more specific implementation schemes, taking nickel metal as an example, the present invention proposes a method for preparing a gallium nitride nanowire array with c-direction growth on a gallium nitride substrate, which is mainly through mixing metal gallium, sodium and nickel in a certain ratio, under a high-pressure nitrogen atmosphere, metal sodium dissociates nitrogen at a high temperature, and forms a Ni2Ga3 alloy phase in the melt, and prepares a gallium nitride nanowire array with c-direction growth on a gallium nitride substrate under the catalytic action of Ni2Ga3. The principle schematic diagram of the preparation of gallium nitride nanowires in a gallium-sodium-nickel melt is shown as follows Figure 1 shown.

[0048] See also Figure 2 As shown, the specific preparation steps of the gallium nitride nanowire array are as follows:

[0049] S1: Raw material ratio; prepare alloy with Ga:Ni=83:17~98:2 ratio (see Figure 5 The Ga-Ni phase diagram shown in the figure) is then mixed with (Ga+Ni):Na=25:75~33:67 to achieve the composition of "liquid phase+Ni2Ga3" in the liquid phase. The mixing process is carried out in a glove box that is free of water and oxygen.

[0050] In the growth temperature range of the present invention, according to Figure 4 The Ga-Na phase diagram shown in the figure shows that Ga and Na are fully miscible in liquid phase (the blue dotted line represents that Ga-Na is a uniform liquid phase at the growth temperature); according to Figure 5The Ga-Ni phase diagram shown in FIG. 1 is a Ga-Ni phase diagram (the dotted line is an interval that can be used as a raw material ratio). Due to the presence of a high-temperature alloy phase, an excessively high Ni component will form an alloy solid phase at the growth temperature of the present invention, and the alloy solid phase may be deposited on the substrate surface and affect the growth; at the same time, the solubility of Ni in Na is extremely low, and the two are almost immiscible with each other. Therefore, in the mixing range, there will be Ni2Ga3 alloy particles (catalytic material) and Ga-Na liquid alloy in the liquid phase. Under a suitable mixing method, the Ni2Ga3 alloy particles will be dispersed in the Ga-Na liquid phase, and a part of them will contact the substrate, thereby realizing the catalytic growth of nanowires at the interface between the Ni2Ga3 alloy particles and the substrate. The schematic diagram of the growth principle is shown in FIG. Figure 3 In addition to Ni, this method can also be extended to other transition metals with catalytic properties such as Fe and Co.

[0051] Compared with the conventional sodium flux method, the present invention has made improvements in the batching. First, liquid metal Ga (melting point 29°C) and refractory metal (i.e., transition metal with catalytic properties) such as Ni (melting point 1455°C) are pre-batch according to a ratio of 83:17 to 98:2, and mixed for 20 to 25 hours in an inert atmosphere at 800 to 950°C to pre-form a liquid alloy, so that Ga and Ni can be effectively mixed and a liquid phase environment can be provided in the subsequent growth process. Subsequently, the pre-prepared Ga-Ni alloy is mixed with metal Na according to a ratio of (Ga+Ni) to Na of 25:75 to 33:67 in the liquid phase system.

[0052] S2: Raw material transfer: After the ingredients are prepared, the raw materials are put into a crucible with a gallium nitride single crystal substrate at the bottom, and moved to a high-pressure chamber under a device that isolates water and oxygen. Nitrogen is then pumped out five times for gas washing to remove water and oxygen in the chamber.

[0053] S3: Pressure control: Using nitrogen as the nitrogen source, the pressure of the GaN nanowire growth process is maintained at 2-4 MPa through gas path control, and the pressure during the growth process is kept stable.

[0054] S4: Temperature control; during the growth process, the temperature is first raised to 630-660°C and maintained for 1-2 hours to provide nucleation points on the substrate, then raised to 800-830°C, grown for 10-15 hours, and then cooled naturally.

[0055] S5: Post-growth processing: After the growth is completed, the crucible is removed from the growth chamber, and anhydrous ethanol is added to the crucible in a fume hood to dissolve the alloy components until the gallium nitride nanowires grown on the substrate are cleaned.

[0056] In summary, the present invention is different from the one-pot mixing of raw materials in the traditional Na flux by pre-alloying the refractory metal Ni and the metal Ga. Under this condition, the preparation of GaN nanowire arrays on the GaN substrate was unexpectedly achieved. The inventor of this case believes that the pre-alloying of the refractory metal Ni and the metal Ga can effectively promote Ni to provide a liquid phase in the subsequent growth, rather than existing in the liquid phase in a solid state, which effectively improves the role of Ni in the liquid phase. According to the Ga-Na phase diagram, the liquid phases of Ga and Na are fully miscible; according to the Ga-Ni phase diagram, due to the presence of a high-temperature alloy phase, an excessively high Ni component will form an alloy solid phase at the growth temperature of the present invention, and the alloy solid phase may be deposited on the substrate surface and affect growth; at the same time, the solubility of Ni in Na is extremely low, and the two are almost immiscible, so there will be Ga-Na liquid alloy and Ni2Ga3 catalytic alloy particles in the liquid phase. Under this formulation method, the Ni2Ga3 alloy particles will be dispersed in the Ga-Na liquid phase, and a part of them will contact the substrate, thereby realizing the catalytic growth of GaN nanowires at the interface between the Ni2Ga3 alloy particles and the substrate.

[0057] Correspondingly, another aspect of an embodiment of the present invention further provides a gallium nitride nanowire array prepared by the aforementioned method.

[0058] Furthermore, the average radius of the gallium nitride nanowires contained in the gallium nitride nanowire array is 80 to 250 nm, and the density of the gallium nitride nanowires is 10 7 cm -2 Magnitude.

[0059] Furthermore, the arrangement of the GaN nanowires grown by the present invention is more orderly, and has higher performance advantages for subsequent potential applications. The present invention can achieve array arrangement mainly because in the liquid phase system, it belongs to near thermodynamic equilibrium growth (the gas phase method is non-thermodynamic equilibrium), so it only needs to be simply oriented through the substrate itself. Induction, it can achieve nanowire array growth, which also shows the simplicity of the method for preparing gallium nitride nanowire arrays in the liquid phase.

[0060] By means of the above technical scheme, compared with the traditional sodium flux method for growing gallium nitride bulk single crystals, the present invention utilizes a liquid phase system of sodium flux, and innovatively prepares high-density gallium nitride nanowire arrays in a nitrogen atmosphere by changing the raw material ratio of sodium-gallium-transition metal with catalytic properties and adjusting the temperature field and pressure field, thereby realizing the preparation of gallium nitride nanowire arrays with c-direction growth on a gallium nitride substrate in a liquid phase system.

[0061] The technical scheme of the present invention is further described in detail below in conjunction with several preferred embodiments and accompanying drawings. Obviously, the described embodiments are only a part of embodiments of the present invention, rather than all embodiments. It should be pointed out that the embodiments described below are intended to facilitate the understanding of the present invention, and do not have any limiting effect on them. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the art without making creative work belong to the scope of protection of the present invention. The experimental methods for which specific conditions are not indicated in the following examples are usually according to conventional conditions, or according to the conditions recommended by the manufacturer. The experimental materials used in the embodiments used below, if not otherwise specified, can all be purchased by conventional biochemical reagent companies.

[0062] Example 1

[0063] The specific steps of the method for preparing gallium nitride nanowire arrays by flux method in this embodiment are as follows:

[0064] S1: Raw material ratio: pre-alloy with Ga:Ni=9:1 ratio, and then mix (Ga+Ni):Na=30:70 to achieve the composition of "liquid phase+Ni2Ga3" in the liquid phase. The mixing process is carried out in a glove box with no water or oxygen. When Ga:Ni is close to 9:1, it may be more conducive to the growth of nanowire arrays.

[0065] S2: Raw material transfer: After the ingredients are prepared, the raw materials are put into a crucible with a gallium nitride single crystal substrate at the bottom, and moved to a high-pressure chamber under a device that isolates water and oxygen. Nitrogen is then pumped out five times for gas washing to remove water and oxygen in the chamber.

[0066] S3: Pressure control: Using nitrogen as the nitrogen source, the pressure of the GaN nanowire growth process is maintained at 3MPa through gas line control, and the pressure during the growth process is kept stable.

[0067] S4: Temperature control; during the growth process, the temperature is first raised to 650°C and maintained for 1 hour to provide nucleation points on the substrate, then raised to 800°C, grown for 10 hours, and then cooled naturally.

[0068] S5: Post-growth processing: After the growth is completed, the crucible is removed from the growth chamber, and anhydrous ethanol is added to the crucible in a fume hood to dissolve the alloy components until the gallium nitride nanowires grown on the substrate are cleaned.

[0069] The surface morphology of the GaN nanowires prepared in this example is shown in the low magnification image. Figure 6 As shown, the high-magnification image of the surface morphology is as follows Figure 7 The gallium nitride nanowires prepared in this embodiment are tilted at 45° and the bird's-eye view is as shown in FIG. Figure 8 As shown, the radius statistics of GaN nanowires are shown in Fig. 9As shown, according to statistics, the average radius of the nanowires is 162±64nm, and the density of the nanowires is about 10 7 cm- 2 Magnitude.

[0070] Example 2

[0071] This embodiment prepares gallium nitride nanowire arrays according to the method of embodiment 1, except that the ratio of Ga:Ni is adjusted to 83:17, (Ga+Ni):Na=30:70. The obtained results are similar to those of embodiment 1, but the nanowire diameter is slightly larger than that of embodiment 1.

[0072] Example 3

[0073] This embodiment prepares gallium nitride nanowire arrays according to the method of embodiment 1, except that the ratio of Ga:Ni is adjusted to 98:2, (Ga+Ni):Na=30:70. The obtained results are similar to those of embodiment 1, but the nanowire diameter is slightly smaller than that of embodiment 1.

[0074] Example 4

[0075] This embodiment prepares gallium nitride nanowire arrays according to the method of embodiment 1, except that the ratio of (Ga+Ni) : Na is adjusted to 25 : 75. The obtained results are similar to those of embodiment 1, but the nanowire diameter is slightly smaller than that of embodiment 1.

[0076] Example 5

[0077] This embodiment prepares gallium nitride nanowire arrays according to the method of embodiment 1, except that the ratio of (Ga+Ni) : Na is adjusted to 33 : 67. The obtained results are similar to those of embodiment 1, but the diameter of the nanowires is slightly larger than that of embodiment 1.

[0078] Example 6

[0079] The gallium nitride nanowire array was prepared according to the method of Example 1, except that the growth temperature was first raised to 630°C and maintained for 2 hours, and then raised to 830°C and grown for 12 hours. The obtained results were similar to those of Example 1, but the nanowire diameter was slightly larger than that of Example 1.

[0080] Example 7

[0081] The gallium nitride nanowire array was prepared according to the method of Example 1, except that the growth temperature was first raised to 660°C and maintained for 1 hour, and then raised to 830°C and grown for 15 hours. The obtained results were similar to those of Example 1, but the nanowire diameter was slightly larger than that of Example 1.

[0082] Example 8

[0083] The gallium nitride nanowire array was prepared according to the method of Example 1, except that the growth pressure was set to 2 MPa. The obtained results were similar to those of Example 1, but the nanowire diameter was slightly smaller than that of Example 1.

[0084] Example 9

[0085] The gallium nitride nanowire array was prepared according to the method of Example 1, except that the growth pressure was set to 4 MPa. The obtained results were similar to those of Example 1, but the nanowire diameter was slightly larger than that of Example 1.

[0086] Example 10

[0087] The gallium nitride nanowire array was prepared according to the method of Example 1, except that Ni in the raw material was replaced by Co. The obtained results were similar to those of Example 1, and the gallium nitride nanowire array was successfully prepared on the substrate.

[0088] Embodiment 11

[0089] The gallium nitride nanowire array was prepared according to the method of Example 1, except that Ni in the raw material was replaced by Fe. The obtained results were similar to those of Example 1, and the gallium nitride nanowire array was successfully prepared on the substrate.

[0090] Comparative Example 1

[0091] Compared with Example 1, the difference is that Ni is not added, and Ga:Na=25:75-33:67.

[0092] This will result in direct epitaxial growth of GaN bulk single crystals on the substrate, and the preparation of nanowires cannot be achieved.

[0093] Comparative Example 2

[0094] Compared with Example 1, the difference is that the content of added Ni is too high (higher than 83:17).

[0095] This will eventually lead to the Ni2Ga3 particles being too large in diameter or being densely distributed, causing the nanowires to have a larger diameter or to merge and grow into a non-nanowire structure.

[0096] Comparative Example 3

[0097] Compared with Example 1, the difference is that the content of added Ni is too low (lower than 98:2).

[0098] This will eventually result in the diameter of the Ni2Ga3 particles in the liquid phase being too small, failing to meet the conditions for catalytic growth and making it impossible to grow a gallium nitride nanowire array.

[0099] Comparative Example 4

[0100] Compared with Example 1, the difference is that the pressure is set to 5 MPa.

[0101] This will lead to a further increase in the nitrogen concentration in the melt, promoting the c-direction growth of GaN, which may cause the nanowires to merge, increase the nanowire diameter, or form a micron-wire structure.

[0102] Comparative Example 6

[0103] Compared with Example 1, the difference is that the pressure is set to 1 MPa.

[0104] This will cause the nitrogen concentration in the melt to decrease, making it impossible for gallium nitride to grow.

[0105] Comparative Example 7

[0106] Compared with Example 1, the difference is that the reaction temperature is 850°C.

[0107] This will lead to an increase in the nitrogen concentration in the melt, but a decrease in supersaturation, which is not conducive to the growth of gallium nitride.

[0108] Comparative Example 8

[0109] Compared with Example 1, the difference is that the reaction temperature is 750°C.

[0110] This will lead to a decrease in the nitrogen concentration in the melt, which is also not conducive to the growth of gallium nitride.

[0111] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments with other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0112] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for preparing a gallium nitride nanowire array by a flux method, characterized in that: include: Providing a liquid phase system comprising an alloy catalytic material of Ga and a transition metal element having catalytic properties, and a Ga-Na liquid phase alloy; Under the condition of isolating water and oxygen, the liquid phase system is brought into contact with a gallium nitride single crystal substrate, and in a high-pressure nitrogen atmosphere, metallic sodium dissociates nitrogen at a high temperature, and a gallium nitride nanowire array is grown in the c direction of the gallium nitride single crystal substrate under the catalytic action of the alloy catalytic material.

2. The method according to claim 1, characterized in that: The transition metal element with catalytic properties includes at least any one of Fe, Co, and Ni; and / or the mass ratio of Ga to the transition metal element with catalytic properties in the alloy catalyst material is 83:17 to 98:2; And / or, the mass ratio of the sum of Ga and the transition metal element with catalytic properties to Na in the liquid phase system is 25:75 to 33:

67.

3. The method according to claim 1, characterized in that include: In an inert atmosphere, a transition metal with catalytic properties is mixed with liquid metal Ga, and mixed at 800 to 950° C. for 20 to 25 hours to achieve full mixing, thereby prefabricating the alloy catalytic material; And / or, the alloy catalytic material comprises alloy catalytic particles having a diameter of 80-200 nm.

4. The method according to claim 1, characterized in that: include: In a water and oxygen removal device, Ga is prepared with a transition metal having catalytic properties to form an alloy catalytic material; And, the alloy catalyst material is mixed with Ga and Na to form a liquid phase system.

5. The method according to claim 1, characterized in that: The alloy catalyst material is dispersed in the Ga-Na liquid phase alloy, wherein a portion of the alloy catalyst material is in contact with the gallium nitride single crystal substrate, thereby achieving catalytic growth of the gallium nitride nanowire array at the interface between the alloy catalyst material and the gallium nitride single crystal substrate.

6. The method according to claim 1, characterized in that include: The liquid phase system is placed in a reaction device containing a gallium nitride single crystal substrate at the bottom, and transferred to a high-pressure reaction chamber under a device isolating water and oxygen; Preferably, the method further comprises: repeatedly inputting and extracting nitrogen into the high-pressure reaction chamber, thereby removing water and oxygen in the high-pressure reaction chamber.

7. The method according to claim 1, characterized in that : The pressure of the high-pressure nitrogen atmosphere is 2-4 MPa.

8. The method according to claim 1, characterized in that include: During the growth process, the temperature is first raised to 630-660°C and maintained for 1-2 hours, and then raised to 800-830°C and grown for 10-15 hours.

9. The method according to claim 1, characterized in that: Also includes: After the growth is completed, the alloy catalytic material on the top of the gallium nitride nanowire array is cleaned with a cleaning agent; preferably, the cleaning agent includes anhydrous ethanol.

10. A gallium nitride nanowire array prepared by the method according to any one of claims 1 to 9; Preferably, the average radius of the gallium nitride nanowires contained in the gallium nitride nanowire array is 80 to 250 nm, and the density of the gallium nitride nanowires is 10 7 cm -2 Magnitude.

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