Estimated phase equilibria in the transition metal-Ga-N systems: Consequences for electrical contacts to GaN

High quality electrical contacts to GaN are required for the advancement of electronic and optoelectronic devices based on the III-V nitrides. In this study, the metallurgy of contacts to GaN and the implications for the design of electrical contacts are considered. First, phase diagrams are estimated for the transition metal-Ga-N systems. The diagrams are then used as an aid in predicting the reaction products of annealed metal/GaN contacts, to suggest materials that may be useful as thermally stable electrical contacts and to explore the role of the partial pressure of N₂ in the annealing environment on the reactions in metal/ GaN contacts. It is believed that this information will be particularly useful to researchers during the early stages of contact development since very little experimental information is currently available on the GaN contact metallurgy.