High pressure direct synthesis of III-V nitrides

The nitrides of group III metals: (AIN, GaN, InN) are very important materials due to their applications for short wavelength optoelectronics (light-emitting diodes and laser diodes). In this paper, the results of high-pressure direct synthesis of AIN, GaN and InN are presented. The conditions for the thermodynamical stability for AIN, GaN and InN are discussed. The influence of the kinetic barrier on the synthesis of InN, GaN and AIN is considered using the results of quantum mechanical calculations of the dissociative adsorption of N-2 on the liquid metal surface. It is shown that the kinetic barrier for InN synthesis is very high, preventing direct synthesis of this compound. This barrier is lower for GaN, which allows to grow GaN crystals from the solution of atomic nitrogen in liquid gallium. The lowest barrier is for AlN, which leads to the combustion reaction of liquid aluminum in nitrogen atmosphere, in the pressure range from 10 to 650 MPa. At higher pressure, the extinction of combustion synthesis takes place. (C) 1999 Published by Elsevier Science B.V. All rights reserved.