Low Resistance and Themarlly Stable Ohmic Contact on p-type GaN Using a RuO2 Diffusion Barrier

Abstract

A low resistance, thermally stable reflective ohmic contact oil p-type GaN was developed using Ru/Ag over-layers oil ail oxidized Ni/Au contact. A specific contact resistivity of <8.4 x 10(-5) Omega cm(2) was maintained during annealing from 300 degrees C to 600 degrees C in O-2 ambient. In addition, the Ni/Au/Ru/Ag contact showed excellent thermal stability after annealing at 500 degrees C for 24 hrs. The RuO2 layer oxidized during oxidation annealing acted as a diffusion barrier for intermixing, of the Ag reflector with the oxidized Ni/Au contact, resulting in enhancement of the thermal stability of the contact.