A β-Ga2O3 nanowire / diamond heterostructure, its preparation method and application

Abstract

This invention discloses a β-Ga₂O₃ nanowire / diamond heterostructure, its preparation method, and its applications. The method includes the following steps: dropping Ga metal droplets onto an auxiliary substrate; placing the diamond substrate and the auxiliary substrate in the same temperature zone of a tube furnace; introducing a mixed gas of H₂ and Ar into the tube furnace under negative pressure, using O₂ entering from the outside and residual O₂ in the tube furnace as the O source, and growing β-Ga₂O₃ nanowires on the diamond surface without catalysis. The method of this invention eliminates the need for additional annealing treatment and pre-laying of metal catalysts on the diamond substrate, and avoids the phenomenon of O₂ etching of the diamond substrate under high-temperature conditions. β-Ga₂O₃ nanowires are epitaxially grown on the diamond surface through the vapor deposition of Ga. This method is simple and low-cost.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, specifically to a β-Ga2O3 nanowire / diamond heterojunction, its preparation method, and its application. Background Technology

[0002] With the development of science and technology, research on low-dimensional nanomaterials, focusing on semiconductor nanostructures, has gradually attracted attention. Semiconductor materials exhibit physical properties different from their macroscopic counterparts due to small size effects, surface effects, volume effects, and quantum tunneling effects. As a novel semiconductor material with an ultra-wide bandgap (4.9 eV) and a high critical electric field (8 MV / cm), β-Ga₂O₃ has attracted widespread attention in electronic device applications. Compared with thin film materials, one-dimensional nanowires, due to their quantum confinement effect, abundant surface states, and significant surface / size effect, can significantly improve the light absorption and carrier transport characteristics of devices. However, the low thermal conductivity of β-Ga₂O₃ makes it difficult for heat to dissipate in related devices in a timely manner, leading to a decrease in carrier mobility and drain current, resulting in a self-heating effect, which is one of the important problems causing low device reliability.

[0003] Using diamond, with its high thermal conductivity, as a heteroepitaxial substrate for β-Ga₂O₃ nanowires can significantly improve the heat dissipation capabilities of semiconductor devices. β-Ga₂O₃ nanowires with this unique nanostructure can broaden the application of materials in high-power / high-temperature electronic devices, high-frequency electronic power devices, and solar-blind photodetectors. As temperature increases, resistivity decreases, potentially leading to better performance of β-Ga₂O₃ nanowire / diamond devices at high operating temperatures and possibly eliminating thermal runaway during high-temperature and / or high-power operation frequently observed in other semiconductors. However, diamond is easily etched by oxygen at high temperatures, resulting in numerous etching pits, thus preventing the use of conventional methods to grow β-Ga₂O₃ nanowires on diamond substrates. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention provides a β-Ga2O3 nanowire / diamond heterostructure, its preparation method, and its application. This method requires no metal catalyst, has a simple preparation process, low growth cost, and avoids the phenomenon of diamond being etched by oxygen at high temperatures, enabling the prepared β-Ga2O3 nanowires to have a better heteroepitaxial orientation relationship with the diamond substrate.

[0005] The technical solution of this invention is achieved as follows: a method for preparing β-Ga2O3 nanowire / diamond heterostructure, comprising the following steps:

[0006] (1) Add liquid metal droplets Ga to the auxiliary substrate layer;

[0007] (2) Place the diamond substrate and the auxiliary substrate in the same temperature zone of the tube furnace;

[0008] (3) The tubular furnace is evacuated to negative pressure, and a mixture of H2 and Ar is introduced. The O2 from outside air entering the tubular furnace and the O2 remaining in the tubular furnace are used as the O source. β-Ga2O3 nanowires are grown on the surface of the diamond substrate by chemical vapor deposition. The tubular furnace is a CVD tubular furnace with a non-completely sealed structure. When the tubular furnace is under negative pressure, outside air will enter the furnace from the unsealed parts of the tubular furnace, and the O2 in the entering air will be used as the O source. In addition, there is no need to purge the tubular furnace, and some air will remain in the tubular furnace, and the O2 in the residual air will be used as the O source.

[0009] Furthermore, in step (3), the flow rate of the mixed gas is 100-200 sccm, the growth temperature is 800-1000℃, the growth pressure is less than 30 Torr, and the growth time is 1-4h.

[0010] Furthermore, the method for adding Ga droplets is as follows: Ga metal stored at 5°C is placed in a 60°C drying oven for 20 minutes and then taken out, and then Ga metal is dropped onto the auxiliary substrate.

[0011] Furthermore, the gas mixture comprises 10% H2 and 90% Ar, referring to volume percentages.

[0012] Furthermore, the auxiliary substrate layer is a Si substrate layer.

[0013] A β-Ga2O3 nanowire / diamond heterostructure is prepared using the method described above.

[0014] An application of a β-Ga2O3 nanowire / diamond heterojunction in vertical devices.

[0015] Furthermore, the vertical device includes a Ti / Au bottom electrode, a β-Ga2O3 nanowire / diamond heterojunction, a PMMA insulating layer, and an ITO top electrode arranged sequentially from bottom to top. The β-Ga2O3 nanowire / diamond heterojunction includes a diamond substrate layer, and β-Ga2O3 nanowires are heteroepitaxially grown on the upper side of the diamond substrate layer.

[0016] Beneficial effects of the present invention

[0017] (1) In this invention, β-Ga2O3 nanowires are grown on the surface of diamond without catalyst and prepared by conventional CVD tube furnace annealing. The preparation conditions are simple and controllable, and it has the prospect of large-scale commercial application.

[0018] (2) The present invention does not require pre-annealing of the diamond substrate and pre-laying of a metal thin film as a catalyst, which simplifies the preparation process and saves production costs.

[0019] (3) The β-Ga2O3 nanowires prepared by this invention have no metal catalyst particles at the top, which improves the quality of the β-Ga2O3 nanowires and broadens the application range of the material.

[0020] (4) Since the presence of oxygen under high temperature conditions can easily etch diamond, H2 / Ar is used as the flowing gas. The O source is provided by the external O2 entering the tube furnace under negative pressure and the residual O2 in the tube furnace, instead of directly using O2 as the reaction gas. This avoids the phenomenon of diamond being etched by oxygen at high temperature, so that the prepared β-Ga2O3 nanowires and diamond substrate can have a better heteroepitaxial orientation relationship.

[0021] (5) The prepared β-Ga2O3 nanowires have a certain epitaxial orientation relationship with the diamond substrate, which significantly improves the crystal quality and thermal conductivity of the β-Ga2O3 nanowires, providing material support for broadening the application of the material in high-power / high-temperature electronic devices, high-frequency electronic power devices and solar-blind photodetectors. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a method for heteroepitaxially growing β-Ga2O3 nanowires on a diamond surface according to the present invention;

[0023] Figure 2 The following are images of the β-Ga2O3 nanowires grown in Example 3: (a) TEM morphology image, (b) HRTEM image, (c) SAED image, (d) EDX mapping image, (e) EDX image, and (f) β-Ga2O3 crystal structure diagram.

[0024] Figure 3 SEM images of β-Ga2O3 nanowires grown in Examples 1-5 and Comparative Example 1;

[0025] Figure 4 Here are the HRTEM images and corresponding FFT images of β-Ga2O3 nanowires grown in Example 3;

[0026] Figure 5 A schematic diagram of the photoelectric performance test of a vertical device with β-Ga2O3 nanowire / diamond heterojunction;

[0027] Figure 6 The band structure diagram of a vertical device for β-Ga2O3 nanowire / diamond heterojunction under Dark / Light conditions. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1:

[0030] like Figure 1 As shown, a method for preparing a β-Ga2O3 nanowire / diamond heterostructure includes the following steps:

[0031] (1) Add Ga metal droplets to the Si substrate and then place it in a conventional CVD tube furnace;

[0032] Pretreatment of Si substrate: The Si substrate was sequentially immersed in acetone, ethanol and deionized water for ultrasonic cleaning for 10 min, and then dried with a high-pressure nitrogen gun.

[0033] Adding liquid Ga metal droplets to the Si substrate: After storing Ga metal at 5°C in a 60°C drying oven for 20 minutes, remove it and use a dropper to draw a small amount of liquid Ga metal and drop it onto the surface of the Si substrate.

[0034] (2) Pretreatment of diamond substrate: The diamond substrate is simply polished; the diamond substrate is then placed in acetone, ethanol and deionized water for ultrasonic cleaning for 10 min in sequence, and then dried with a high-pressure nitrogen gun.

[0035] The pretreated diamond substrate and the auxiliary substrate were placed in the same ceramic boat and then placed in a CVD tube furnace. The diamond substrate was placed close to the auxiliary substrate and downstream of the auxiliary substrate.

[0036] (3) In a conventional CVD tube furnace, H2 (10% H2 and 90% Ar) = 200 sccm, growth temperature is 1000℃, growth pressure is 28 Torr, growth time is 1h, and residual O2 in the tube furnace is used to provide oxygen source to grow β-Ga2O3 nanowires on the surface of diamond substrate.

[0037] Figure 3 (a) is a SEM image of the β-Ga2O3 nanowires grown in this embodiment. The prepared sample consists of coarse microrods or irregularly shaped microstructures with a rough surface, and is heteroepitaxially grown from the surface of a diamond substrate.

[0038] This invention first uses a simple physical method to drop liquid Ga onto the surface of a Si substrate, and then further grows β-Ga₂O₃ nanowires on a diamond surface through heat treatment in a conventional tube furnace. The Ga source for growing the β-Ga₂O₃ nanowires in this invention comes from the liquid Ga droplets on the Si substrate surface, and the O source comes from residual O₂ in the tube furnace and O₂ introduced from outside air under negative pressure. Throughout the growth process, no metal catalyst is introduced, and no direct O source is introduced, avoiding contact between the β-Ga₂O₃ nanowires and the metal or Ga droplets. Therefore, during the high-temperature treatment, the diamond substrate is not etched by oxygen, and the β-Ga₂O₃ nanowires are not contaminated by Ga, thereby improving the quality of the β-Ga₂O₃ nanowires and achieving a heteroepitaxial orientation relationship between the β-Ga₂O₃ nanowires and the diamond substrate, solving the problem that β-Ga₂O₃ nanowires cannot be heteroepitaxially grown on the diamond surface.

[0039] This invention utilizes diamond, with its high thermal conductivity, as a heteroepitaxial substrate for β-Ga2O3 nanowires, which significantly improves the heat dissipation capability of semiconductor devices. β-Ga2O3 nanowires with this unique nanostructure can broaden the application of materials in high-power / high-temperature electronic devices, high-frequency electronic power devices, and solar-blind photodetectors.

[0040] Example 2:

[0041] This embodiment is basically the same as embodiment 1, except that in step (3), other growth parameters are kept unchanged, and β-Ga2O3 nanowires are grown on the surface of the diamond substrate for 2 hours.

[0042] Figure 3 (b) is a SEM image of the β-Ga2O3 nanowires grown in this embodiment, compared with the β-Ga2O3 nanowires grown for 1 h in Example 1. Figure 3 (a) In comparison, the length of the nanowires increases while the diameter decreases.

[0043] Example 3:

[0044] This embodiment is basically the same as that of embodiment 1, except that in step (3), other growth parameters are kept unchanged, and β-Ga2O3 nanowires are grown on the surface of the diamond substrate for 3 hours.

[0045] Figure 2 (ac) shows the TEM morphology, HRTEM image, and corresponding SAED image of the β-Ga2O3 nanowires grown in this embodiment. Figure 2 (a) shows the broken β-Ga2O3 nanowire scraped off the diamond surface with a copper mesh. It can be seen that the diameter of the broken β-Ga2O3 nanowire is about 100 nm and the length is about 2 μm. Figure 2(b, c) High-resolution TEM shows that the β-Ga2O3 nanowires have high crystallinity. SAED diffraction spots show that the band axis of the β-Ga2O3 nanowires is ZA =

[002] , which corresponds well to the PDF card of β-Ga2O3 (JCPDS card No. 00-011-0370). Figure 2 (d, e) are the EDX mapping diagram and EDX spectrum of the β-Ga2O3 nanowires grown in this embodiment. It can be seen that Ga and O elements are uniformly distributed on the β-Ga2O3 nanowires in an atomic ratio of 2:3. Figure 2 (f) is the crystal structure diagram of β-Ga2O3. β-Ga2O3 is a monoclinic crystal system. Ga atoms have two different positions, which are surrounded by O atoms to form a regular tetrahedron and a regular octahedron, respectively. O atoms have three different positions.

[0046] Figure 3 (c) is a SEM image of the β-Ga2O3 nanowires grown in this embodiment. In areas closer to the diamond, larger bulk β-Ga2O3 nanowires grow directly from the diamond surface, and the contact between the β-Ga2O3 nanowires and the diamond is clearly visible. Furthermore, the bulk β-Ga2O3 nanowires tend to grow into slender strips.

[0047] Figure 4 The images show HRTEM images and corresponding FFTs of the epitaxially grown β-Ga2O3 nanowires in Example 3 of this invention. The HRTEM images and FFTs show that the β-Ga2O3 nanowires have a good heteroepitaxial orientation relationship with the diamond substrate.

[0048] Example 4:

[0049] This embodiment is basically the same as that of embodiment 1, except that in step (3), other growth parameters are kept unchanged, and β-Ga2O3 nanowires are grown on the surface of the diamond substrate for 4 hours.

[0050] Figure 3 (d) is a SEM image of the β-Ga2O3 nanowires grown in this embodiment. The bottom of the β-Ga2O3 nanowires has a heteroepitaxial orientation with the diamond substrate, while the top covers the entire diamond substrate. The length increases while the diameter decreases, resulting in large-scale β-Ga2O3 nanowires with smooth surfaces and high aspect ratios. These β-Ga2O3 nanowires can reach lengths of several hundred micrometers. Therefore, increasing the heat treatment time can significantly improve the aspect ratio of the β-Ga2O3 nanowires.

[0051] Example 5:

[0052] This embodiment is basically the same as that of embodiment 1, except that in step (3), other growth parameters are kept unchanged, the growth temperature is 850℃, and β-Ga2O3 nanowires are grown on the surface of the diamond substrate for 3 hours.

[0053] Figure 3 (f) is a SEM image of the β-Ga2O3 nanowires grown in this embodiment. Bulk β-Ga2O3 is grown on the surface of the diamond substrate, which shows that increasing the temperature can promote the growth of β-Ga2O3 nanobulks into nanowires.

[0054] Comparative Example 1:

[0055] This embodiment is basically the same as embodiment 1, except that in step (3), other growth parameters are kept unchanged, Ar is introduced into the tube furnace, and β-Ga2O3 nanowires are grown on the surface of the diamond substrate for 3 hours.

[0056] Figure 3 (e) is a SEM image of the β-Ga2O3 nanowires grown in this embodiment. The surface of the β-Ga2O3 nanowires is relatively rough, which shows that the introduction of H2 can make the surface of the β-Ga2O3 nanowires smooth.

[0057] Example 6

[0058] An application of a β-Ga2O3 nanowire / diamond heterojunction is disclosed in a vertical device. The vertical device comprises, from bottom to top, a Ti / Au bottom electrode, a β-Ga2O3 nanowire / diamond heterojunction, a PMMA insulating layer, and an ITO top electrode. The β-Ga2O3 nanowire / diamond heterojunction includes a diamond substrate layer, on which β-Ga2O3 nanowires are heteroepitaxially grown.

[0059] The fabrication method of the vertical device is as follows: a 40 nm Ti film and an 80 nm Au film are deposited at the bottom of a diamond substrate using magnetron sputtering as the bottom electrode; a 1 μm PMMA layer is spin-coated on the top side of the β-Ga2O3 nanowire layer as the insulating layer; and a 100 nm ITO layer is magnetron sputtered on top of the PMMA insulating layer as the top electrode.

[0060] Figure 5 A schematic diagram of the photoelectric performance test of a vertical device with β-Ga2O3 nanowire / diamond heterojunction; Figure 6Dark / Light band structure diagram for measuring the optoelectronic performance of a vertical device based on a β-Ga₂O₃ nanowire / diamond heterostructure. In the absence of light, charge carriers diffuse from high-concentration regions to low-concentration regions, forming a space charge region at the interface and creating a built-in electric field to maintain the balance between carrier diffusion and drift. Under illumination, high-energy photons excite β-Ga₂O₃ and diamond to form photogenerated electron-hole pairs within the built-in electric field. Under the influence of the built-in electric field, photogenerated holes move from β-Ga₂O₃ to diamond, and photogenerated electrons move from diamond to β-Ga₂O₃.

Claims

1. A method for preparing β-Ga2O3 nanowire / diamond heterostructure, characterized in that, Includes the following steps: (1) Add liquid metal droplets Ga to the auxiliary substrate layer; (2) Place the diamond substrate and the auxiliary substrate in the same temperature zone of the tube furnace; (3) Evacuate the tube furnace to negative pressure and introduce a mixture of H2 and Ar gas. Use the O2 from the outside air entering the tube furnace and the O2 remaining in the tube furnace as the O source. β-Ga2O3 nanowires are grown on the surface of the diamond substrate by chemical vapor deposition. The flow rate of the mixed gas was 100-200 sccm, the growth temperature was 800-1000℃, the growth pressure was less than 30 Torr, and the growth time was 1-4 h.

2. The method for preparing a β-Ga2O3 nanowire / diamond heterostructure according to claim 1, characterized in that, In step (1), the method of adding metal droplets Ga is as follows: after keeping the metal Ga stored at 5°C in a 60°C drying oven for 20 minutes, take it out and then drop the metal Ga onto the auxiliary substrate.

3. The method for preparing a β-Ga2O3 nanowire / diamond heterostructure according to claim 1, characterized in that, The gas mixture consists of 10% H2 and 90% Ar.

4. The method for preparing a β-Ga2O3 nanowire / diamond heterostructure according to claim 1, characterized in that, The auxiliary substrate layer is a Si substrate layer.

5. A β-Ga2O3 nanowire / diamond heterostructure, characterized in that, Prepared using the method described in any one of claims 1-4.

6. The application of the β-Ga2O3 nanowire / diamond heterostructure according to claim 5, characterized in that, Applied to vertical devices.

7. The application according to claim 6, characterized in that, The vertical device includes, from bottom to top, a Ti / Au bottom electrode, a β-Ga2O3 nanowire / diamond heterojunction, a PMMA insulating layer, and an ITO top electrode. The β-Ga2O3 nanowire / diamond heterojunction includes a diamond substrate layer, and β-Ga2O3 nanowires are heteroepitaxially grown on the upper side of the diamond substrate layer.

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