Investigations of the growth conditions for GaN-bulk crystals grown by the sublimation technique

Spontaneous nucleation of GaN and the growth of thick polycrystalline layers by the sublimation technique in nitrogen atmosphere have been studied as a function of growth environment and conditions. Average growth rates higher than 10 microns per hour were realised by reaction of gallium, evaporated from an elemental source, with nitrogen from ammonia gas. The growth temperature was in the range of 1000 1300 degrees C; the pressure was varied between 200 - 800 hPa and the ammonia flow between 50-500 sccm min(-1). It was found that the growth rate only moderately decreases during a long-term experiment when using an optimised set of growth parameters. Furthermore, a strong influence of the growth environment on the growth rate and impurity content was found. (c) 2007 WELEY-VCH Verlag GmbH & Co. KGaA, Weinheim.