Sublimation Sandwich Method (SSM) [1] has proven successfully in the growth of both bulk AlN and SiC [2,3] and shows promise for growth of bulk GaN crystals as well. In our investigations, GaN layers were grown by the SSM. Experiments were carried out in a tubular quartz reactor with induction heating at temperatures from 1100OC to 1250OC. GaN layers, grown on Al2O3, obtained by MOCVD were used as the substrate. The area of deposition was 10x10mm. Monocrystaline GaN layers were obtained under atmospheric pressure during a deposition time from 5 to 60 minutes. GaN powder was used as the source of gallium and ammonia as the source of nitrogen. GaN powder and the substrate were placed in a quartz boat on top of a graphite cylinder, which was the heating element. To ensure gallium transfer, temperature gradient was employed between the gallium source and the MOCVD substrate. The obtained GaN layers possessed irregular surface morphology with a thickness range up to 1mm. Raman spectroscopy and X-ray studies were used to investigate the films.
[1] P.G. Baranov et al., MRS Internet J. Nitride Semicond. Res. 3, 50 (1998),
[2] J.H. Edgar et al., J. Cryst.Growth 246 (2002) 187,
[3] Y. Shi et al., J. Cryst.Growth 233 (2001) 177.