Effects of Solution Stirring on the Growth of Bulk GaN Single Crystals by Na Flux Method

Recently, we succeeded in fabricating centimeter-sized bulk gallium nitride (GaN) crystals with large dislocation-free areas on a GaN point seed. However, problems of polycrystal formation, skeletal growth, and low growth rate still remained. In this study, to suppress skeletal growth, polycrystals formation and increase the growth rate, we introduced two types of solution-stirring techniques-rotating stirring and swinging stirring-in the growth on point seeds by the Na flux method. We found that increasing the reversal frequency of the rotating stirring and increasing the rate of the swinging stirring increased the growth rate and suppressed the formation of polycrystals and skeletal growth. Moreover, the maximum c-direction growth rate of 46 mu m/h was achieved without the formation of polycrystals and skeletal growth. We conclude that solution stirring may be an effective technique for fabricating high-quality large bulk GaN crystals. (C) 2013 The Japan Society of Applied Physics