Ohmic contacts to p-type GaN using a Ni/Pt/Au metallization scheme

We report a new Ni/Pt/Au trilayer metallization scheme for the formation of ohmic contact to p-GaN. Metal thin films with a thickness of 20 nm for Ni, 30 nm for Pt, and 80 nm for Au were deposited on the p-GaN layer (Na=9.4×1016 cm−3) by electron beam evaporation. The samples, annealed at 500 °C for 30 s in a rapid thermal anneal system, showed a high quality ohmic contact with a low specific contact resistance of 2.1×10−2 Ω cm2. Auger electron spectroscopy analysis of the contact layers suggests that Pt plays an important role in the formation of ohmic contact, indicating that a Ni/Pt/Au trilayer can be used and that it is a promising material system for ohmic contact to p-GaN.