Non-polar gallium nitride substrate material with inverted V-shaped structure as well as preparation method and application of non-polar gallium nitride substrate material

Abstract

The invention belongs to the technical field of semiconductor devices, and relates to a non-polar gallium nitride single crystal substrate material with an inverted V-shaped structure and a preparation method and application thereof. The method comprises the following steps: cleaning a sapphire (Al2O3) substrate, and depositing a silicon dioxide mask on the Al2O3 substrate by using an electron beam evaporation method; and controlling different growth time through a hydride vapor phase epitaxial growth means after photoetching, and epitaxially forming a non-polar GaN single crystal substrate material with an inverted V-shaped structure. The process technology is simple, efficient and high in universality, and large-scale production is facilitated; and moreover, the dislocation density of the GaN crystal is remarkably reduced, and the crystal quality is remarkably improved. The non-polar surface GaN single crystal with the inverted V-shaped structure is used as a substrate material to be applied to a GaN-based light-emitting device, and the light-emitting efficiency of the GaN-based light-emitting device is obviously enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor devices and relates to a non-polar gallium nitride single crystal substrate material with an inverted "V" structure and a preparation method and application thereof. Background Art

[0002] At present, semiconductor materials based on group IV or group III-V materials, by virtue of their physical and chemical properties, regulate various optoelectronic properties of corresponding semiconductor technologies, enabling the interaction and control of electrons, holes and photons from different device structures and environments in a wide range of applications. For example, silicon and germanium-based materials, which were originally used in the first transistors, have expanded and revolutionized modern industrial systems. However, these materials still have different inherent limitations such as operational failures in harsh environments and low power handling capabilities.

[0003] Wide bandgap semiconductors can improve device performance as their bandgap increases, and wider bandgap semiconductors have obvious potential advantages. Among them, gallium nitride (GaN) has the advantages of large bandgap width, strong breakdown electric field, low on-resistance, high electron mobility and high conversion efficiency, and is used in blue, green, ultraviolet laser diodes, light-emitting diodes (LEDs) and high electron mobility transistors. At the same time, the integration and process compatibility of GaN devices with silicon-based complementary metal oxide semiconductor devices make it possible to break through the current limitations of Moore's Law. However, most of the substrate materials used in the preparation of commercial LEDs are heteroepitaxially grown GaN films, which have large dislocation density and residual stress, thereby limiting the incorporation of indium (In) elements and non-radiative recombination centers, reducing the luminous efficiency of commercial LEDs; in addition, the growth direction of the commercial LED device structure is mostly concentrated in the

[0001] crystal phase, so there are spontaneous and piezoelectric polarization electric fields, which reduces the quantum efficiency of the multiple quantum wells in the LED device and increases the energy loss. Compared with polar GaN single crystals, non-polar GaN single crystals eliminate the quantum confined Stark effect caused by the polarization electric field and have therefore attracted widespread attention.

[0004] However, the current technical means for preparing non-polar GaN crystals mainly include wet etching, bottom-up template method, etc. These methods generally have defects such as complicated and cumbersome processes, the need for multiple equipment, high costs, and long preparation cycles. It is not easy to popularize large-scale industrial production of non-polar GaN crystals. Therefore, it is necessary to find a simple, fast, and low-cost method for preparing high-quality non-polar GaN single crystals and corresponding LED light-emitting devices. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a non-polar gallium nitride single crystal substrate material with an inverted "V" structure and a preparation method and application thereof, and specifically relates to a non-polar GaN single crystal substrate material for high-performance LEDs.

[0006] A method for preparing a non-polar gallium nitride single crystal substrate material having an inverted "V" structure comprises the following steps: (1) Depositing a silicon dioxide (SiO2) mask on a sapphire (Al2O3) substrate by electron beam evaporation; preferably, the Al2O3 substrate is cleaned with acetone, ethanol, and deionized water in sequence before evaporation, and then purged with high-purity nitrogen to clean the surface; (2) performing photolithography on the Al2O3 substrate with the SiO2 mask in step (1) using a photolithography process; (3) Using hydride vapor phase epitaxy (HVPE) growth means, the material after photolithography in step (2) is used as a substrate, and the growth time and temperature are controlled to epitaxially form a non-polar GaN single crystal substrate material with an inverted "V" structure.

[0007] Preferably, according to the present invention, in step (1), the cleaning time of the wafer surface is 30 min, and the purity of the nitrogen is 99.99%.

[0008] Preferably according to the present invention, the thickness of the SiO2 mask in step (1) is 50-150 nm.

[0009] Preferably, according to the present invention, during the SiO2 evaporation process in step (1), the temperature inside the chamber is 200-400°C and remains constant.

[0010] Preferably, according to the present invention, the pattern produced by photolithography in step (2) is a circle, the diameter of the circle is 500 nm to 2 μm, the spacing is 1 to 5 μm, and the depth is 2 to 4 μm.

[0011] Preferably, according to the present invention, in the HVPE growth in step (3), GaCl2, HCl and ammonia are used as raw materials for epitaxy, and the epitaxial growth time is 10-60 min, preferably 20 min; the growth temperature is 850-1000 °C.

[0012] The present invention also includes a non-polar gallium nitride single crystal substrate material with an inverted "V" structure obtained by the above preparation method, and the application of the non-polar gallium nitride single crystal substrate material in a GaN-based light-emitting device.

[0013] The present invention uses hydride vapor phase epitaxy (HVPE) technology to directly prepare a non-polar GaN single crystal with a uniformly distributed inverted "V" structure on a sapphire (Al2O3) substrate by utilizing the competitive growth relationship between various crystal planes. The non-polar GaN single crystal with the prepared inverted "V" structure is used as a substrate material, and InGaN / GaN multiple quantum wells are directly epitaxially grown on the substrate by using metal organic vapor phase deposition technology. Tests have shown that the luminous performance of the LED prepared on the porous non-polar GaN single crystal substrate is significantly enhanced. This is because the presence of pores enables photoexcitons to directly enter the interior of the GaN lattice through the pore structure, reducing scattering. At the same time, after pretreatment of the non-polar GaN single crystal, the dislocation density of the crystal is significantly reduced, thereby reducing the non-radiative scattering center in the LED device, thereby improving the light extraction efficiency.

[0014] Compared with the prior art, the present invention has the following advantages: (1) The present invention utilizes the different growth rates of each crystal face of the gallium nitride crystal and controls different growth times to directly grow a non-polar face GaN single crystal with an inverted "V" structure on a sapphire substrate without the need for complex chemical reaction and other preparation processes. The process technology is simple, efficient, and highly versatile, and is conducive to large-scale production. (2) This method is not only conducive to the exposure of the non-polar surface of the GaN crystal, but also significantly reduces the dislocation density and significantly improves the crystal quality; (3) The non-polar GaN single crystal with an inverted "V" structure is used as the substrate material for LED devices, and its luminous brightness and luminous efficiency are significantly enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a scanning electron microscope image of the non-polar GaN single crystal with an inverted “V” structure obtained in Example 1; Figure 2 This is a cathode fluorescence microscope image of the non-polar surface GaN single crystal with an inverted “V” structure obtained in Example 1; Figure 3 is a scanning electron microscope image in Example 2; Figure 4 It is the scanning electron microscope image in Comparative Example 1; Figure 5 It is the cathode fluorescence microscope image in Comparative Example 1; Figure 6 This is a comparison chart of the photoluminescence intensity in Experimental Example 1. DETAILED DESCRIPTION

[0016] The present invention will be further described below in conjunction with specific embodiments, and the advantages and features of the present invention will become clearer as the description proceeds. However, the embodiments are exemplary only and do not constitute any limitation to the scope of the present invention. It should be understood by those skilled in the art that the details and forms of the technical solution of the present invention may be modified or replaced without departing from the spirit and scope of the present invention, but these modifications and replacements all fall within the scope of protection of the present invention.

[0017] Example 1 A method for preparing a non-polar gallium nitride single crystal substrate material with an inverted "V" structure (1) A 100 nm silicon dioxide (SiO2) mask was deposited on a sapphire (Al2O3) substrate by electron beam evaporation, and the temperature in the chamber was maintained at a constant temperature of 300 °C; the Al2O3 substrate was cleaned with acetone, ethanol, and deionized water for 30 min in sequence before evaporation, and then purged with high-purity nitrogen (purity of 99.99%) to clean the surface; (2) using a photolithography process, etching a circular pattern with a diameter of 800 nm, a pitch of 2 μm, and a depth of 2.5 μm on the Al2O3 substrate with the SiO2 mask in step (1); (3) The Al2O3 with the circular pattern SiO2 mask in step (2) is used as the substrate and GaCl 2、 HCl and ammonia were used as raw materials, the reaction temperature was set at 985 °C, and the reaction time was 20 min, so that GaN single crystal epitaxy was carried out on SiO2 / Al2O3 substrate to form GaN single crystal with an inverted "V" structure, thereby exposing more non-polar faces. The corresponding scanning electron microscope images are shown in Figure 2. Figure 1 shown.

[0018] The dislocation density of the GaN single crystal with an inverted "V"-shaped non-polar surface prepared in step (3) was observed using a cathode fluorescence microscope. Figure 2 shown.

[0019] The acceleration voltage was set to 5 kV, the aperture was selected to 60 μm, the working distance between the sample stage and the electron collector was adjusted to 11.2 mm, and a suitable observation position was selected. After repeated focusing and adjustment of astigmatism, it can be clearly seen that there are many "black spot" areas on the surface of the original GaN single crystal material. This area is the dislocation area of ​​the GaN single crystal.

[0020] Application of a non-polar gallium nitride single crystal substrate material with an inverted "V" structure (1) The GaN single crystal with an inverted “V” structure having a non-polar surface prepared in Example 1 was cut into a regular shape of 10×15 mm by laser cutting; (2) The cut GaN crystal is cleaned with acetone, ethanol, and deionized water in sequence, and then purged with high-purity nitrogen to clean the surface; (3) Using MOCVD technology, trimethyl indium, trimethyl gallium and ammonia as raw materials, and the gas flow rates are 2-5 sccm, 200-300 sccm and 8-20 slm respectively, at a growth temperature of 850 °C, an InGaN / GaN multi-quantum well structure is deposited on the surface of the sample in step (2); and a GaN-based LED device is obtained.

[0021] Example 2 A method for preparing a non-polar gallium nitride single crystal substrate material with an inverted "V" structure The difference from Example 1 is that the reaction time in step (3) is 45 min. The experimental results show that under the same process conditions, due to the long reaction time, the reactants GaCl2, HCl and NH3 were fully reacted, and GaN basically achieved uniform growth, with a relatively flat surface, most of the non-polar faces tended to merge, and the exposed surface was reduced. This caused the LED device prepared as a substrate to have a strong polarization electric field, resulting in the quantum confined Stark effect and increasing the energy loss of the device. The corresponding scanning electron microscope image is shown below. Figure 3 shown.

[0022] Comparative Example 1 A method for preparing gallium nitride single crystal substrate material The difference from Example 1 is that the reaction time in step (3) is 90 min, and a GaN single crystal is obtained.

[0023] The experimental results show that under the same process conditions, GaN single crystals can be grown uniformly on the patterned sapphire substrate. Scanning electron microscope observation shows that the surface of the epitaxial wafer is relatively uniform and a large number of non-polar surfaces are not exposed. Figure 4 As shown. It can be seen from the cathode fluorescence microscope that the dislocation density of the sample is significantly higher than the dislocation density of the GaN single crystal with an inverted "V" structure prepared in Example 1, proving that the generation of the inverted "V" structure not only exposes more non-polar surfaces, but also improves the crystal quality of the GaN single crystal. The corresponding cathode fluorescence microscope image is shown in Figure 5 shown.

[0024] Application of a gallium nitride single crystal substrate material (1) Cutting the GaN single crystal obtained above into a regular shape of 10×15 mm by laser cutting; (2) The cut GaN single crystal is cleaned with acetone, ethanol, and deionized water in sequence, and then purged with high-purity nitrogen to clean the surface; (3) Using MOCVD technology, trimethyl indium, trimethyl gallium and ammonia as raw materials, and the gas flow rates are 2-5 sccm, 200-300 sccm and 8-20 slm respectively, at a growth temperature of 850 °C, an InGaN / GaN multi-quantum well structure is deposited on the surface of the sample in step (2); and a GaN-based LED device is obtained.

[0025] Comparative Example 2 A method for preparing a non-polar gallium nitride single crystal substrate material with an inverted "V" structure The difference from Example 1 is that the reaction time in step (3) is 5 min.

[0026] The experimental results show that under the same other process conditions, due to the short reaction time, the GaN single crystal is in the early stage of growth and does not show an obvious complete morphology structure. A relatively uneven distribution feature appears on the surface, which may lead to the In doping amount being blocked in the later process of LED device preparation, thereby affecting the luminescence performance of the device.

[0027] Test Example 1 The luminescence performance of the GaN-based LED devices prepared in Example 1 and Comparative Example 1 was tested by photoluminescence spectroscopy, with the wavelength set to 300-700 nm and the excitation voltage set to 10 kV.

[0028] The test results show that the luminous intensity of the LED device prepared from the non-polar GaN single crystal with an inverted "V" structure in Example 1 is about five times stronger than that of the LED device prepared from the flat GaN single crystal in Comparative Example 1 (e.g. Figure 6 As shown in the figure, it is proved that the non-polar GaN single crystal with inverted "V" structure can effectively improve the luminous performance of LED light-emitting devices and reduce the energy loss of devices by reducing dislocation density and multi-wall utilization efficiency. The process is simple and universal, which is conducive to large-scale production.

Claims

1. A method for preparing a non-polar gallium nitride single crystal substrate material having an inverted "V" structure, characterized in that: The preparation method comprises the following steps: (1) Depositing a silicon dioxide (SiO2) mask on a sapphire (Al2O3) substrate by electron beam evaporation; preferably, the Al2O3 substrate is cleaned with acetone, ethanol, and deionized water in sequence before evaporation, and then purged with high-purity nitrogen to clean the surface; (2) performing photolithography on the Al2O3 substrate with the SiO2 mask in step (1) using a photolithography process; (3) Using hydride vapor phase epitaxy (HVPE) growth means, the material after photolithography in step (2) is used as a substrate, and the growth time and temperature are controlled to epitaxially form a non-polar GaN single crystal substrate material with an inverted "V" structure.

2. The preparation method according to claim 1, characterized in that In the step (1), the cleaning time of the wafer surface is 30 min, and the purity of the nitrogen is 99.99%.

3. The preparation method according to claim 1, characterized in that The thickness of the SiO2 mask in step (1) is 50-150 nm.

4. The preparation method according to claim 1, characterized in that During the SiO2 evaporation process in step (1), the temperature inside the chamber is 200-400°C and remains constant.

5. The preparation method according to claim 1, characterized in that The pattern produced after photolithography in step (2) is a circle, the diameter of the circle is 500 nm~2 μm, the spacing is 1~5 μm, and the depth is 2~4 μm.

6. The preparation method according to claim 1, characterized in that: In the step (3), the HVPE growth uses GaCl2, HCl and ammonia as raw materials for epitaxy.

7. The preparation method according to claim 1, characterized in that The time of epitaxial growth in step (3) is 10 to 60 min, preferably 20 min.

8. The preparation method according to claim 1, characterized in that: The temperature of the epitaxial growth in step (3) is 850-1000°C.

9. A non-polar GaN single crystal substrate material having an inverted "V"-shaped structure obtained by the preparation method according to any one of claims 1 to 8.

10. Application of the non-polar GaN single crystal substrate material with an inverted "V"-shaped structure as claimed in claim 9 in GaN-based light-emitting devices.

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