Growing bulk aluminum nitride and gallium nitride crystals by the sublimation sandwich method

The review of the results of growth of bulk Al and Ga nitride crystals on foreign substrates by the sublimation sandwich method (SSM) is presented. The kinetics and the mechanism of sublimation and condensation nitrides depending on the growth conditions, structure of the vapor phase, crystal orientation and the distance between the source and the seed are analyzed. It is experimentally established that by joint annealing of AlN and SiC the rate of AlN sublimation significantly increases due to formation of a liquid phase on the crystal surface. Non-uniform distribution of the liquid phase localized mainly near structural and morphological defects results in the selective nature of the surface etching, and also is the reason of deterioration of the growing crystal quality. The process of bulk AlN crystals growth with simultaneous evaporation of the seed allowing to grow crystals without cracks and with the improved parameters is realized. On SiC seeds bulk AlN crystals from 0.5 to 2 inch in diameter are grown.