Ohmic Contacts To P-Type Al0.45ga0.55n

Ni, Pd, and Au Ohmic contacts to p-Al0.45Ga0.55N have been examined. We have observed that annealing the contacts in excess of 800degreesC is required to minimize the contact resistivity. However, the Pd and Au contacts annealed in excess of 700degreesC, which showed much better transport properties than Ni contacts annealed at the same temperatures, suffered from a rapid photoinduced degradation of both the current-voltage characteristics of the contacts and of the sheet resistance of the p-Al0.45Ga0.55N itself. This degradation was greatly reduced by passivating the p-Al0.45Ga0.55N surface with a SiNx film. A hypothesis is presented to describe the observed degradation. (C) 2004 American Institute of Physics.