Kinetics and mechanism of thermal decomposition of GaN

A scheme of dissociative evaporation of GaN with the partial evolution of nitrogen in the form of free atoms has been invoked to interpret the decomposition mechanism of GaN in vacuum or inert gas atmosphere. A critical analysis of literature data and their comparison with theoretical calculations has shown that the main kinetic characteristics of decomposition, including the absolute decomposition rate and activation energy are in full agreement with the reaction: GaN(s) → Ga(g)+0.5N+0.25N2. Condensation of the gallium vapor in the reaction zone and partial transport of condensation energy to GaN account for the features which are typical of many solid-state reactions and manifest themselves in the appearance of induction and acceleration periods in the course of the process. The low temperature decomposition of GaN in H2 according to the equilibrium reaction GaN(s)+1.5H2=Ga(g)+NH3 is supported by a good agreement of experimental and calculated activation energies and by the strong inhibition effect of NH3 on the GaN decomposition. As expected, condensation of Ga vapor in the Ga(l)/GaN(s) interface accelerates the reduction of GaN by H2 several hundred times.