Gallium nitride nanowire and thin film symbiotic single crystal structure and preparation method thereof

Abstract

This invention relates to the field of semiconductor materials technology, and discloses a gallium nitride nanowire and thin film co-existing single-crystal structure and its preparation method. The preparation method of the gallium nitride nanowire and thin film co-existing single-crystal structure provided by this invention involves chemical vapor deposition (CVD) on a lithium aluminate substrate with a metal catalyst layer on its surface. The metal catalyst-assisted gaseous growth species transport induces gallium nitride nucleation, growing into a gallium nitride thin film structure. Then, the metal catalyst initiates the growth of gallium nitride nanowires along three equivalent crystal directions through a gas-liquid-solid growth mechanism, resulting in their orderly arrangement. The bottoms of the nanowires are connected by the thin film phase, and the nanowires are interconnected to form a structural basis with a continuous conductive path. The preparation method of this invention is simple, effective, and low-cost. By selecting a lithium aluminate substrate of suitable size, the desired gallium nitride nanowire and thin film co-existing single-crystal structure can be obtained.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor materials technology, specifically relating to a gallium nitride nanowire and thin film co-existing single crystal structure and its preparation method. Background Technology

[0002] Gallium nitride (GaN) possesses a wide bandgap, high breakdown field strength, high carrier mobility, and good thermal stability, making it widely used in optoelectronic devices, radio frequency devices, and power electronic devices. One-dimensional GaN nanostructures exhibit a large specific surface area and significant anisotropy, which is beneficial for improving light absorption, light emission, carrier transport, and surface sensitivity.

[0003] However, dispersed or disordered gallium nitride nanowires are typically discontinuous, requiring complex positioning, transfer, interconnection, and electrode fabrication steps during subsequent device fabrication, increasing process difficulty and device consistency risks. If ordered gallium nitride nanowires can be formed in situ on a single-crystal substrate and connected at the bottom of the nanowires via a gallium nitride thin film, a continuous semiconductor structure more suitable for device fabrication can be formed while retaining the high specific surface area advantage of one-dimensional nanostructures.

[0004] Therefore, it is necessary to provide a symbiotic single-crystal structure and its preparation method that can simultaneously form gallium nitride nanowires and gallium nitride thin films on a single-crystal substrate and give them a defined epitaxial orientation relationship. Summary of the Invention

[0005] The purpose of this invention is to provide a gallium nitride nanowire and thin film co-existing single crystal structure and its preparation method, so as to solve the problems of nanowires being dispersed, difficult to interconnect, and complex subsequent device fabrication in existing gallium nitride nanowire structures.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: On one hand, the present invention provides a gallium nitride nanowire and thin film co-existing single crystal structure, comprising: Lithium aluminate single crystal substrate; Gallium nitride thin film on lithium aluminate single crystal substrate; And several gallium nitride nanowires epitaxially grown integrally with the gallium nitride thin film; In this structure, several gallium nitride nanowires are arranged along three equivalent crystal orientations on a lithium aluminate single crystal substrate, and the bottoms of the several gallium nitride nanowires are interconnected through gallium nitride thin films.

[0007] The "connection" or "connection" mentioned in this invention mainly refers to the continuous structural connection formed at the bottom of the gallium nitride nanowires through a gallium nitride thin film, and is not necessarily limited by the results of electrical conductivity tests. Through this structure, dispersed one-dimensional gallium nitride nanowires can form a continuous gallium nitride semiconductor structure with the help of the bottom gallium nitride thin film, which helps to reduce the difficulty of nanowire positioning, transfer, and interconnection fabrication in subsequent device fabrication processes.

[0008] Preferably, the lithium aluminate single crystal substrate is a (100)-plane lithium aluminate single crystal substrate.

[0009] Preferably, the gallium nitride nanowires and gallium nitride thin films are epitaxial symbiotic structures.

[0010] The epitaxial symbiotic structure described in this invention refers to the formation of gallium nitride thin films and gallium nitride nanowires during the same growth process, with the two interconnected in space and having an orientation relationship induced by a lithium aluminate single crystal substrate.

[0011] Preferably, the crystal planes of the gallium nitride nanowires and thin films are any m-planes of gallium nitride.

[0012] More preferably, the crystal planes of the gallium nitride nanowires and thin films are gallium nitride

[10] . 0] Crystal plane.

[0013] Preferably, the three equivalent crystal orientations include gallium nitride [1] 00]、[10 0] and [01 [0] Or three adjacent m crystal directions equivalent to the above crystal direction, gallium nitride thin films are grown on lithium aluminate substrates along any one of the three equivalent m crystal directions.

[0014] More preferably, the gallium nitride thin film is applied along

[10] on the lithium aluminate substrate. 0] Growth.

[0015] Preferably, the diameter of the gallium nitride nanowire is 1 nm to 5 μm and the length is 10 nm to 100 μm; the thickness of the gallium nitride film is 10 nm to 1000 μm.

[0016] On the other hand, the present invention also provides a method for preparing the above-mentioned gallium nitride nanowire and thin film co-existing single crystal structure, comprising the following steps: S1. Provide a lithium aluminate single crystal substrate, clean and dry the lithium aluminate single crystal substrate to obtain a clean lithium aluminate single crystal substrate. S2. A metal catalyst layer is formed on the surface of a clean lithium aluminate single crystal substrate to obtain a lithium aluminate single crystal substrate covered with a metal catalyst layer. S3. Place the lithium aluminate single crystal substrate covered with a metal catalyst layer in a chemical vapor deposition reaction chamber, so that the gallium-containing gaseous species generated by the gallium source react with the nitrogen source near the lithium aluminate single crystal substrate to form a gallium nitride thin film on the lithium aluminate single crystal substrate, and grow gallium nitride nanowires arranged along three equivalent crystal orientations on the gallium nitride thin film to obtain a single crystal structure of gallium nitride nanowires and thin film coexisting.

[0017] During the growth process, the metal catalyst layer covering the surface of the lithium aluminate single crystal substrate forms metal catalyst particles as the temperature rises. Gallium-containing gaseous species generated by the gallium source react with the nitrogen source near the substrate, forming a gallium nitride nucleation layer on the surface of the lithium aluminate single crystal substrate and gradually forming a gallium nitride thin film. At the same time, some metal catalyst particles are enriched with gallium-containing species and can induce gallium nitride nanowires to grow epitaxially from the surface of the gallium nitride thin film through a gas-liquid-solid growth mechanism. Due to the specific epitaxial orientation relationship between the (100) plane lithium aluminate single crystal substrate and gallium nitride, the gallium nitride nanowires preferentially align along the three equivalent crystal orientations on the surface of the lithium aluminate single crystal substrate, thereby forming an epitaxial structure in which gallium nitride nanowires and gallium nitride thin films coexist.

[0018] Preferably, in S1, the lithium aluminate single crystal substrate is a (100) plane lithium aluminate single crystal substrate.

[0019] Preferably, in S1, the size of the lithium aluminate single crystal substrate is 2 mm × 2 mm to 50 mm × 50 mm.

[0020] Preferably, in S1, the cleaning and drying process is as follows: the lithium aluminate single crystal substrate is sequentially placed in an organic solvent and deionized water for ultrasonic cleaning, and then dried with nitrogen gas to obtain a clean lithium aluminate single crystal substrate.

[0021] Preferably, the organic solvent includes one or more of acetone and ethanol.

[0022] Preferably, in S2, the metal catalyst layer is one or more of gold, iron, nickel, copper, cobalt, and indium.

[0023] More preferably, in S2, the metal catalyst layer is a gold catalyst layer.

[0024] Preferably, in S2, the metal catalyst layer is formed by magnetron sputtering, vapor deposition, or immersion.

[0025] More preferably, in S2, the metal catalyst layer is formed by magnetron sputtering.

[0026] Preferably, in S2, the thickness of the metal catalyst layer is 1 nm to 40 nm.

[0027] More preferably, in S2, the thickness of the metal catalyst layer is 10 nm to 20 nm.

[0028] Preferably, when magnetron sputtering is used to form the metal catalyst layer, the sputtering gas is argon, the sputtering pressure is 0.1 Pa to 5 Pa, the sputtering voltage is 10 V to 100 V, and the sputtering current is 0.005 A to 0.1 A.

[0029] In this invention, the thickness and continuity of the metal catalyst layer, as well as the size of the metal catalyst particles formed after subsequent heating, affect the nucleation density, diameter, and distribution of gallium nitride nanowires. By adjusting the thickness of the metal catalyst layer and the formation conditions, the morphology of the gallium nitride nanowire and thin film co-structure can be adjusted.

[0030] Preferably, in S3, the reaction temperature is 650℃~1050℃.

[0031] More preferably, in S3, the reaction temperature is 800℃~950℃.

[0032] Preferably, in S3, the reaction pressure is 3 kPa to 50 kPa.

[0033] More preferably, in S3, the reaction pressure is 20 kPa to 35 kPa.

[0034] Preferably, in S3, the reaction time is 10 min to 150 min.

[0035] More preferably, in S3, the reaction time is 30 min to 90 min.

[0036] Preferably, in S3, the gallium source is one or a combination of metallic gallium, gallium oxide, trimethylgallium, and triethylgallium.

[0037] More preferably, in S3, the gallium source is metallic gallium.

[0038] Preferably, in S3, the nitrogen source is ammonia, and the ammonia flow rate is 10 sccm to 5000 sccm.

[0039] More preferably, the ammonia flow rate is 300 sccm to 1000 sccm.

[0040] Preferably, in S3, the carrier gas is a mixture of nitrogen and hydrogen, with a volume ratio of nitrogen to hydrogen of 1:20 to 25:1.

[0041] More preferably, the volume ratio of nitrogen to hydrogen is 1:1 to 8:1.

[0042] In S3, reaction temperature, reaction pressure, reaction time, ammonia flow rate, carrier gas composition, and metal catalyst layer thickness can be used to adjust the thickness of gallium nitride thin films, the diameter, length, density, and orientation of gallium nitride nanowires.

[0043] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention forms gallium nitride thin films and gallium nitride nanowires in situ on a lithium aluminate single crystal substrate. The gallium nitride nanowires and gallium nitride thin films are epitaxially grown integrally to form a gallium nitride nanowire / thin film symbiotic structure with structural continuity.

[0044] 2. The gallium nitride nanowires of the present invention are arranged along three equivalent crystal orientations on a lithium aluminate single crystal substrate, which is beneficial to improving the orientation consistency of the nanowire structure compared with the disordered dispersed nanowire structure.

[0045] 3. The gallium nitride nanowires of the present invention are interconnected at the bottom by gallium nitride thin films. While maintaining the advantages of high specific surface area and anisotropic structure of one-dimensional nanowires, this method helps to reduce the difficulty of positioning, transfer and interconnection processing in subsequent device fabrication.

[0046] 4. This invention employs chemical vapor deposition to directly prepare gallium nitride nanowire and thin film co-structures on a lithium aluminate single-crystal substrate covered with a metal catalyst layer. The process involves fewer steps and is suitable for preparing gallium nitride nanowire / thin film composite epitaxial structures with specific orientation relationships. Attached Figure Description

[0047] Figure 1 This is a scanning electron microscope image of the gallium nitride nanowire and thin film co-occurring single crystal structure prepared in Example 1 of the present invention; Figure 2 The image shows the X-ray diffraction pattern of the gallium nitride nanowire and thin film co-occurring single crystal structure prepared in Example 1 of this invention. Figure 3 This is a selected area electron diffraction pattern of the gallium nitride nanowires prepared in Example 1 of the present invention using transmission electron microscopy; Figure 4 This is a scanning electron microscope image of the gallium nitride nanowire and thin film co-occurring single crystal structure prepared in Example 2 of the present invention; Figure 5 The image shows the room-temperature photoluminescence spectrum of the gallium nitride nanowire and thin film co-occurring single crystal structure prepared in Example 2 of this invention. Figure 6 This is a scanning electron microscope (SEM) image of the surface of the sample obtained in Comparative Example 1 without the deposition of an Au catalyst layer. Detailed Implementation

[0048] To enable those skilled in the art to better understand the present application, the technical solutions in specific embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by those skilled in the art.

[0049] Example 1 This embodiment provides a method for preparing a gallium nitride nanowire and thin film co-existing single crystal structure, including the following steps: S1. Provide a (100) facet lithium aluminate single crystal substrate with a size of 10 mm × 10 mm. Place the lithium aluminate single crystal substrate in acetone, anhydrous ethanol and deionized water in sequence for ultrasonic cleaning for 20 min each. After taking it out, blow it dry with nitrogen to obtain a clean lithium aluminate single crystal substrate.

[0050] S2. Place the clean lithium aluminate single crystal substrate into the magnetron sputtering system and evacuate the cavity background vacuum to 1×10⁻⁶. -6 Argon gas was introduced to maintain the chamber pressure at 0.5 Pa. Gold sputtering was performed under sputtering voltage of 35 V and sputtering current of 0.02 A to form an Au catalyst layer with a thickness of about 10 nm on the surface of the lithium aluminate single crystal substrate, thus obtaining a lithium aluminate single crystal substrate covered with an Au catalyst layer.

[0051] S3. Using metallic gallium as the gallium source, a lithium aluminate single-crystal substrate covered with an Au catalyst layer is placed in the isothermal zone of a chemical vapor deposition furnace. This isothermal zone is the reaction area where gallium vapor species and ammonia gas meet. Before the reaction, nitrogen gas is introduced into the furnace for 10 minutes to remove residual air and water vapor. Then, the pressure is evacuated to a low pressure of approximately 0.2 Pa, and then 2000 sccm of nitrogen gas is introduced to maintain the chamber pressure at 32 kPa.

[0052] After heating the furnace to 850℃, a nitrogen / hydrogen mixed carrier gas and ammonia were introduced simultaneously, with a nitrogen to hydrogen volume ratio of 7:1 and an ammonia flow rate of 900 sccm. The reaction was carried out at 850℃ for 60 min. After the reaction was completed, heating was stopped, and the sample was removed after the furnace was allowed to cool naturally to room temperature, yielding a gallium nitride nanowire and thin film co-existing single crystal structure.

[0053] The sample obtained in Example 1 was tested using a scanning electron microscope. Figure 1 The results show that a large number of gallium nitride nanowires are formed on the sample surface. The gallium nitride nanowires are aligned along three crystal directions, and a continuous thin film structure can be observed at the bottom of the nanowires.

[0054] The sample obtained in Example 1 was subjected to X-ray diffraction testing. Figure 2 The results showed that gallium nitride and lithium aluminate substrate-related diffraction peaks were observed in the sample, while no other obvious impurity phase peaks were observed, indicating that a gallium nitride structure was formed on the lithium aluminate single crystal substrate.

[0055] The single gallium nitride nanowire obtained in Example 1 was subjected to selected area electron diffraction (SEM) analysis using transmission electron microscopy. Figure 3 The selected area electron diffraction spots are regularly distributed, indicating that the obtained gallium nitride nanowires have single-crystal characteristics.

[0056] Example 2 The gallium nitride nanowire and thin film co-existing single crystal structure was prepared according to the method of Example 1. The difference from Example 1 is that in S3, the cavity pressure was maintained at 27 kPa, the ammonia flow rate was 600 sccm, and the volume ratio of nitrogen to hydrogen was 5:1.

[0057] The sample obtained in Example 2 was tested using a scanning electron microscope. Figure 4 The results show that a large number of gallium nitride nanowires are formed on the surface of the sample obtained in Example 2, and the nanowires are observed to be aligned in three directions. Compared with Example 1, the distribution density of gallium nitride nanowires in the sample obtained in Example 2 is higher.

[0058] The sample obtained in Example 2 was subjected to room temperature photoluminescence testing. Figure 5 The results show that the sample exhibits a near-band edge emission peak around 361 nm, indicating that the obtained gallium nitride nanowire and thin film co-structure has ultraviolet luminescence properties.

[0059] Comparative Example 1 The experiment was conducted according to the method of Example 1, except that in S2, an Au catalyst layer was not deposited on the surface of the lithium aluminate single crystal substrate.

[0060] The surface of the obtained sample was observed using a scanning electron microscope after the experiment. Figure 6 The results show that no obvious gallium nitride nanowire and thin film symbiotic structure was formed on the substrate surface, and the surface morphology was basically consistent with that of the lithium aluminate single crystal substrate before growth. This result indicates that, under the conditions of this embodiment, the Au catalyst layer plays an important role in the formation of the gallium nitride nanowire and thin film symbiotic structure.

[0061] Other implementation methods In other embodiments, the size of the lithium aluminate single crystal substrate can be selected from 2 mm × 2 mm to 50 mm × 50 mm to meet the processing requirements of samples or devices of different sizes.

[0062] In other embodiments, the metal catalyst layer can be one or more of gold, iron, nickel, copper, cobalt, and indium; the metal catalyst layer can be formed by magnetron sputtering, vapor deposition, or immersion. By adjusting the material, thickness, and formation method of the metal catalyst layer, the size and distribution of the catalyst particles can be adjusted, thereby adjusting the diameter, density, and distribution morphology of the gallium nitride nanowires.

[0063] In other embodiments, the gallium source can be one or a combination of metallic gallium, gallium oxide, trimethylgallium, and triethylgallium; the nitrogen source can be ammonia; and the carrier gas can be a mixture of nitrogen and hydrogen. The thickness of the gallium nitride film, the length of the gallium nitride nanowires, and the nanowire arrangement can be adjusted by regulating the reaction temperature, reaction pressure, reaction time, ammonia flow rate, and carrier gas ratio.

[0064] In other embodiments, the gallium nitride thin film and gallium nitride nanowires can be formed in the same chemical vapor deposition process. The gallium nitride thin film can serve as a connecting layer at the bottom of the gallium nitride nanowires, enabling structural continuity between multiple gallium nitride nanowires.

[0065] In other embodiments, the resulting gallium nitride nanowire and thin film co-existing single crystal structure can be used as a semiconductor material or structural unit in ultraviolet light-emitting devices, photodetectors, sensors, radio frequency devices, or power electronic devices.

[0066] Finally, it should be noted that the described embodiments are merely some, not all, of the embodiments of the present invention. Those skilled in the art will understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the claims and their equivalents; that is, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A gallium nitride nanowire and thin film coexisting single crystal structure, characterized by, include: Lithium aluminate single crystal substrate; Gallium nitride thin film on lithium aluminate single crystal substrate; And several gallium nitride nanowires epitaxially grown integrally with the gallium nitride thin film; Among them, several gallium nitride nanowires are arranged along three equivalent crystal orientations on the lithium aluminate single crystal substrate, and the bottoms of the several gallium nitride nanowires are interconnected through gallium nitride thin films.

2. The gallium nitride nanowire and thin film intergrown single crystal structure of claim 1, wherein, The lithium aluminate single crystal substrate is a (100) plane lithium aluminate single crystal substrate.

3. The gallium nitride nanowire and thin film co-existing single crystal structure according to claim 1, characterized in that, Three equivalent crystal directions include [1 00], [10 0], and [01 0] of gallium nitride or three adjacent m crystal directions equivalent to the above crystal directions.

4. The gallium nitride nanowire and thin film co-existing single crystal structure according to claim 1, characterized in that, Gallium nitride nanowires have a diameter of 1 nm to 5 μm and a length of 10 nm to 100 μm; gallium nitride films have a thickness of 10 nm to 1000 μm.

5. A method of preparing the gallium nitride nanowire and thin film coexisting single crystal structure according to any one of claims 1 to 4, characterized by, Includes the following steps: S1. Provide a lithium aluminate single crystal substrate, clean and dry the lithium aluminate single crystal substrate to obtain a clean lithium aluminate single crystal substrate. S2. A metal catalyst layer is formed on the surface of a clean lithium aluminate single crystal substrate to obtain a lithium aluminate single crystal substrate covered with a metal catalyst layer. S3. The lithium aluminate single crystal substrate covered with the metal catalyst layer is placed in a chemical vapor deposition reaction chamber, and the gallium-containing gaseous species generated by the gallium source react with the nitrogen source near the lithium aluminate single crystal substrate to form a gallium nitride thin film on the lithium aluminate single crystal substrate, and gallium nitride nanowires arranged along three equivalent crystal orientations are grown on the gallium nitride thin film.

6. The production method according to claim 5, wherein In S2, the metal catalyst layer is one or more of gold, iron, nickel, copper, cobalt, and indium.

7. The preparation method according to claim 5, characterized in that, In S2, the metal catalyst layer is formed by magnetron sputtering, vapor deposition or immersion, and has a thickness of 1~40 nm.

8. The preparation method according to claim 5, characterized in that, In S3, the reaction temperature is 650~1050 ℃, the reaction pressure is 3~50 kPa, and the reaction time is 10~150 min.

9. The preparation method according to claim 5, characterized in that, In S3, the gallium source is one or a combination of metallic gallium, gallium oxide, trimethylgallium, and triethylgallium; the nitrogen source is ammonia, and the ammonia flow rate is 10~5000 sccm.

10. The method of claim 5, wherein, In S3, the carrier gas is a mixture of nitrogen and hydrogen, with a nitrogen to hydrogen volume ratio of 1:20 to 25:1.

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