Growing Bulk Aluminum Nitride and Gallium Nitride Crystals by the Sublimation Sandwich Method

The results of the growth of bulk crystals of aluminum and gallium nitrides on foreign seeds by the sublimation sandwich method are reviewed. The kinetics and mechanism of sublimation and condensation are analyzed depending on the growth conditions, vapor phase composition, crystal orientation, and the distance between the source and the seed. It is experimentally found that during joint annealing of aluminum nitride and silicon carbide, the sublimation rate of aluminum nitride substantially increases due to the formation of a liquid phase on the crystal surface. The inhomogeneous distribution of the liquid phase, localized mainly near structural and morphological defects, leads to the selective nature of surface etching and causes a deterioration in the quality of the growing crystal. A process of growth of bulk AlN crystals with simultaneous seed evaporation was implemented, which yields crystals without cracks and with improved parameters. Bulk crystals of aluminum nitride and gallium nitride up to 2 inches in diameter were grown on SiC seeds.