X-RAY-EXAMINATION OF GAN SINGLE-CRYSTALS GROWN AT HIGH HYDROSTATIC-PRESSURE

Gallium nitride single crystals grown at temperatures 1200-1600-degrees-C and pressures 12-20 kbar were examined with X-ray diffractometry. The narrow (about 20 arc sec) peaks of the (00.4) reflection obtained with a non-dispersive double crystal arrangement proved the high crystallographic perfection of the plate-like crystals. This enabled the measurement of lattice constants using the highly accurate Bond method. The analysis of a set of symmetrical and asymmetrical reflections gave the following values of GaN lattice constants: a = 3.1879 +/- 0.0003 angstrom and c = 5.1856 +/- 0.0001 angstrom.