Low resistance Ti/Pt/Au ohmic contacts to p -type GaN

Electrical properties of Ti (15 nm)/Pt (50 nm)/Au (80 nm) contacts on moderately doped p-GaN (NA=3.0×1017 cm−3) are reported. Linear current–voltage characteristics were observed after annealing the contacts for 1 min at temperatures above 700 °C. The best ohmic contacts were obtained after annealing in a N2 ambient at 800 °C for 2 min. These contacts exhibited a specific contact resistance Rc of 4.2×10−5 Ω cm2 and contact resistivity ρc of 21 Ω mm. Possible mechanisms for the lower contact resistivity of Ti/Pt/Au contacts are discussed. The processing for the Ti/Pt/Au ohmic contacts is compatible with routine fabrication steps for GaN devices.