Preparation method of composite substrate for GaN growth

Abstract

The invention discloses a preparation method of a composite substrate for GaN growth, which comprises the following steps: firstly, growing a GaN single-crystal epitaxial layer on a sapphire substrate; then, attaching a GaN epitaxial wafer to a temporary substrate through an epoxy quick-drying adhesive, and carrying out laser stripping on the sapphire substrate; finally, bonding the GaN epitaxial wafer on the temporary substrate and a heat and electric conducting substrate together, and removing the temporary substrate so as to obtain a composite substrate consisting of a GaN layer with an upturned gallium polar surface and the heat and electric conducting substrate which are bonded together. If the GaN layer on the sapphire substrate and the heat and electric conducting substrate are bonded together, through carrying out laser stripping on the sapphire substrate, a composite substrate consisting of a GaN layer with an upturned gallium polar surface and the heat and electric conducting substrate which are bonded together is obtained. The composite substrate prepared according to the invention takes homoepitaxy into consideration so as to improve the quality of crystals, and can directly prepare a vertical-structured LED (light-emitting diode); and because only a GaN single crystal is used, the cost is greatly reduced, and the composite substrate has great advantages in applications.

Description

technical field [0001] The invention relates to the technical fields of semiconductor optoelectronic devices and metal organic chemical vapor deposition (MOCVD), in particular to a method for preparing a composite substrate for growing GaN epitaxial wafers. Background technique [0002] The Ⅲ / Ⅴ nitride mainly composed of GaN, InGaN and AlGaN is a semiconductor material that has attracted much attention in recent years. It has a continuously variable direct bandgap of 1.9-6.2eV, excellent physical and chemical stability, and high saturation electron mobility. And other characteristics, making it the most preferred material for optoelectronic devices such as lasers and light-emitting diodes. [0003] However, for current GaN-based semiconductor material devices, due to the lack of GaN substrates, the epitaxial films of GaN-based LEDs are usually grown on sapphire substrates, SiC, Si and other substrates. So far, the epitaxial growth technology of GaN material system is basica...

AI Technical Summary

Problems solved by technology

The main problems are: 1. Due to the large lattice mismatch and thermal stress mismatch between GaN and sapphire, resulting in 10 9 cm -2 The misfit dislocations seriously affect the crystal quality and reduce the luminous efficiency and service life 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

However, the high price of GaN single crystal substrate directly restricts its application in LED devices

At present, the price of a 2-inch GaN single crystal substrate can reach 2,000 US dollars, while the current market price of a 2-inch high-power LED epitaxial wafer does not exceed 100 US dollars. Such a huge cost completely limits the application of GaN single crystal substrates in the LED market. application

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