Ohmic contacts to p-type GaN based on TaN, TiN, and ZrN

摘要

Ohmic contacts to p-GaN using a Ni/Au/X/Ti/Au metallization scheme, where X is TaN, TiN, or ZrN, are reported. The dependence of the contact properties on annealing temperature (25-1000℃) in N_2 is examined. For annealing temperatures greater than 500℃, the contacts display Ohmic characteristics and reach a minimum of about 2 X 10~(-4) Ω cm~2 after annealing at 700℃ for 60 s in a N_2 ambient. The specific contact resistance is stable on annealing up to at least 1000℃. However, at high temperatures the morphology of the contacts are very rough and there is a large degree of intermixing between the metallic layers. The thermal stability of these contacts are superior as compared to conventional Ni/Au, which display poor characteristics at annealing temperatures greater than 500℃.