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 (N-A = 3.0x10(17)cm(-3)) are reported. Linear current-voltage characteristics were observed after annealing the contacts for 1 min at temperatures above 700 degrees C. The best ohmic contacts were obtained after annealing in a Na ambient at 800 degrees C for 2 min. These contacts exhibited a specific contact resistance R-c of 4.2x10(-5) Omega cm(2) and contact resistivity rho(c) of 21 Omega 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. (C) 2000 American Institute of Physics. [S0003-6951(00)03723-2].