The Effects of Substrate Surface Treatments on Growth of a-Plane GaN Single Crystals Using Na Flux Method

Nonpolar GaN substrates are necessary for the improvement of GaN device performance. The growth of high-quality nonpolar GaN crystals, however, has not yet been achieved. In this study, we grew a-plane GaN crystals using the Na flux method and investigated the effects of the substrate surface treatment on the crystallinity of grown GaN crystals. A-plane GaN substrates with chemical mechanical polishing (CMP) and with chemical etching using pyrophosphoric acid were used as the seed substrates. We found that full width at the half-maximum (FWHM) of the X-ray rocking curve (XRC) of GaN crystals grown on the substrate with chemical etching was smaller than that on the substrate with CMP. The results show that chemical etching is more effective than CMP for improving the crystallinity of a-plane GaN crystals. (C) 2012 The Japan Society of Applied Physics