Study On The Growth Of Ga N Crystals In Liquid Epitaxial Phase By The Compound Flux Method

Gallium nitride(GaN)has been widely used in the fields of optoelectronics,microelectronics,high-temperature high-power,and high-frequency microwave devices.In order to improve device performance,high-quality GaN bulk single crystals are required to make the substrates.The Na-flux method has the potential to grow GaN single crystals with high quality and low dislocation density.To improve the Na flux method and improve the solubility of nitrogen and the quality of GaN crystals.A large number of experimental studies were carried out by liquid phase epitaxy technique of composite flux.and the main research work and results are as follows:By precisely adjusting the growth temperature and pressure to adjust the supersaturation in the solution,liquid phase epitaxy(LPE)was successfully realized on the10 mm×10.5 mm HVPE-GaN seed crystals,and the surface of the GaN crystal of liquid phase epitaxy changed from a vertically grown rough surface to a layer by layer smooth surface.Secondly,it is found that adding argon can inhibit the volatilization of Na,but argon will affect the dissociation of nitrogen,thus greatly reducing the solubility of nitrogen.The shape of GaN crystals was changed from pyramidal to prismatic to platelet in sequence with the increase of Li-Ca content in the Ga-Na flux,and LPE-GaN can become transparent.It is proposed that the growth of LPE-GaN by the pre-stirring process can improve the solubility of nitrogen and enhance the internal convection of the solution,making the GaN crystal yield reach 95.6%,and increasing the growth thickness of LPE-GaN crystal is about 412 μm.The results of the photoluminescence test and X-ray single crystal diffraction show that the structure quality of LPE-GaN crystal can be improved by pre-stirring.The Bridgman method was developed,and the translucent,relatively flat surface and high-quality GaN single crystal was successfully obtained on GaN seed crystal.GaN crystal shows a typical hexagonal layered growth mode,which indicates that LPEGaN crystal has reached near-equilibrium growth in the solution.The photoluminescence analysis showed that GaN crystal with good structure and quality was obtained by the Bridgman method.