Method for preparing gallium nitride single-crystal substrate by prefabricating cracks

Abstract

The invention discloses a method for preparing a gallium nitride single-crystal substrate by prefabricating cracks. The method is characterized in that the edge of a foreign substrate is treated by integrating technologies such as crack prefabrication, MOCVD (metal organic chemical vapor deposition), HVPE (High Voltage Paper Electrophoresis) and stress control automatic separation, then an MOCVD growth technology is optimized and is matched with a specific crack prefabrication method, and gaps are introduced into the edges of interfaces of GaN and the foreign substrate and serve as prefabricated cracks; the gradient change of the internal stress of a plane from the edge to the center is realized through the stress control technology; the GaN and the foreign substrate are completely and automatically separated under the effect of certain gradient stress, so that the large-sized complete GaN single-crystal substrate is obtained. By adopting the method, the self-supporting GaN single-crystal substrate is obtained, has smooth surface and is flawless and high in crystalline quality. The method has the advantages that the automatic separation of the in-situ GaN and the foreign substrate is realized, additional complicated equipment technologies such as laser lift-off or metal sacrificial layer deposition are not needed, the process is simple and easy to control, and the practicability of the method is greatly improved.

Description

technical field [0001] The invention relates to the field of photoelectric materials and devices, in particular to a method for preparing a gallium nitride single crystal substrate by prefabricating cracks. Background technique [0002] Gallium nitride GaN-based III / V group nitrides are important wide-bandgap semiconductor materials with direct bandgap. It has broad application prospects in fields such as power electronic devices and other optoelectronic devices and electronic devices, as well as semiconductor devices under special conditions. [0003] Due to the extremely high melting temperature and high nitrogen saturation vapor pressure, it is very difficult to prepare large-area GaN single crystals, and GaN-based devices have to be grown heterogeneously on sapphire or silicon carbide substrates with large mismatches. Although this heteroepitaxy technology based on buffer layer technology has achieved great success, this method cannot give full play to the superior perf...

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Problems solved by technology

[0003] Due to the extremely high melting temperature and high nitrogen saturation vapor pressure, it is very difficult to prepare large-area GaN single crystals, and GaN-based devices have to be grown heterogeneously on substrates such as sapphire or silicon carbide with large mismatches.

Although this heteroepitaxy technology based on buffer layer technology has achieved great success, this method cannot give full play to the superior performance of GaN-based semiconductor materials. The main problems are: 1. Due to the large gap between GaN and sapphire lattice mismatch and thermal stress mismatch, resulting in 10 9 cm -2 The misfit dislocations seriously affect the crystal quality and reduce the luminous efficiency of LED; 2. Sapphire is an insulator, and its resistivity is greater than 10 at room temperature 11 Ωcm, so that it is impossible to make a device with a vertical structure, usually only N-type and P-type electrodes can be made on the upper surface of the epitaxial layer, so the effective light-emitting area is reduced, and the photolithography and etching process in the device preparation is increased. Reduce the utilization rate of materials; 3. The thermal conductivity of sapphire is not good, and the thermal conductivity at 100 °C is about 0.25W / cm K, which has a great impact on the performance of GaN-based devices, especially in large-area and high-power devices , the problem of heat dissipation is very prominent; 4. In the production of GaN-based lasers, due to the high hardness of sapphire, and there is a 30-degree angle between the sapphire lattice and the GaN lattice, it is difficult to obtain a solution for the GaN-based LD epitaxial layer. Therefore, the GaN single crystal substrate is also of great significance for the fabrication of GaN-based lasers.

However, these methods have disadvantages such as complicated equipment, difficult separation, easy breakage of GaN single crystal thick film, and low yield, which makes the price of GaN single crystal substrate remain high.

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