A method for preparing the gallium nitride monocrystal substrate

Abstract

The invention provides a method for preparing a GaN single crystal substrate, which belongs to the field of photoelectric materials and devices. The method includes: growing a high-quality GaN film on a heterogeneous substrate such as sapphire using techniques such as MOCVD or MBE as a template for subsequent growth, with a thickness within 10 μm; preparing a flexible weak bond and layer on the GaN template; using conventional The HVPE method rapidly grows a GaN single crystal thick film on a GaN template; due to the reduction of the stress effect between GaN and the substrate, a GaN epitaxial layer with a low dislocation density can be obtained, preventing cracks in the thick film, and obtaining high-quality GaN materials. When the thickness of the GaN single crystal thick film is more than 0.1 mm, the GaN single crystal thick film can be automatically separated from the GaN template during the cooling process to obtain the GaN single crystal thick film. The invention utilizes a weak connection method to improve the crystal quality, to automatically separate the GaN single crystal thick film from the heterogeneous substrate, and directly obtain the GaN single crystal substrate.

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 (GaN) single crystal substrate. Background technique [0002] GaN-based III-V nitrides are important direct-bandgap wide-bandgap semiconductor materials. Due to its unique bandgap range, excellent optical and electrical properties, excellent mechanical and chemical properties of materials, it can be used in blue, green, purple, ultraviolet and white light-emitting diodes (LED), short-wavelength laser diodes (LD), ultraviolet light Optoelectronic devices and electronic devices such as detectors and power electronic devices, as well as semiconductor devices under special conditions, have broad application prospects and attract people's strong interest. [0003] At present, the main methods of growing GaN substrates are the direct reaction preparation method of nitrogen and metal gallium under high temperature and high pres...

AI Technical Summary

Problems solved by technology

The main problem is due to the lattice mismatch and thermal expansion coefficient mismatch between the substrate material sapphire and the GaN epitaxial film (the thermal expansion coefficient of hexagonal wurtzite structure GaN is Δa / a=5.59×10-6 / K; Δc / c=3.17×10-6 / K (300-700K); 7.75×10-6 / K (700-900K), the thermal expansion coefficient of Al2O3 is Δa / a=7.5×10-6 / K; Δc / c=8.5×10-6 / K), from the a-axis of the mutual contact surface, the thermal expansion coefficient mismatch of GaN and Al2O3 is as high as 34%. When the epitaxial film reaches tens of microns, it will crack due to stress and cannot be obtained. Large-scale self-supporting substrate wafers, an international problem

The preparation of GaN single crystal substrates by HVPE mainly solves two major problems: one is the crystal quality (dislocation and cracking) of GaN thick films; the other is the separation of GaN thick films and substrates

[0006] The above separation method of GaN thick film and substrate cannot give full play to the superior performance of GaN-based semiconductor materials. The main problems are 1. The GaN material on the sacrificial substrate has poor crystal quality, and due to the large lattice mismatch The thickness of the grown GaN film is also limited; 2. Large-area GaN thick film and sapphire substrate cannot be separated; 2. The process is complicated and the equipment is expensive, which is not suitable for low-cost mass production

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