Growth of AlN Single Crystals

Abstract

ABSTRACTAluminum nitride is a wurtzite structure III–V compound, although epitaxial layers of zincblende structure AIN have been made. AlN melts congruently at 2750°C with dissociation pressure of 9 atmospheres. Boules of AIN have been successfully grown by a sublimation-recondensation technique at 2300°C employing tungsten crucibles. Growth rates of 0.3 mm per hour were attained at 1 bar pressure of N2, and crystals up to 22 mm long have been grown. An analysis of the growth process shows that the 9.75eV dissociation energy of N2is the limiting factor in the growth rate. The growth rate is predicted to depend on the N2pressure, but no experiments in this area have yet been concluded. The most satisfactory crucible material found so far for growing AIN is single crystal tungsten.