12 - Growth of AlN and GaN crystals by sublimation

Abstract

This chapter reviews the results of growing bulk aluminum nitride (AlN) and gallium nitride (GaN) crystals on foreign substrates by the sublimation sandwich method. We analyzed the kinetics and the mechanism of sublimation and condensation of nitrides depending on the growth conditions, structure of the vapor phase, crystal orientation and the distance between the source and the seed. It is experimentally established that by joint annealing of AlN and silicon carbide (SiC), the rate of AlN sublimation significantly increases due to formation of a liquid phase on the crystal surface. Nonuniform distribution of the liquid phase localized mainly near structural and morphological defects results in the selective nature of the surface etching, and also causes deterioration of the quality of the growing crystal. The process of bulk AlN crystal growth with simultaneous evaporation of the seed allowing formation of crystals without cracks and with improved parameters is discussed. On SiC seeds, bulk AlN and GaN crystals up to 1–2inchin diameter are grown.