Transparent ohmic contacts of oxidized Ru and Ir on p-type GaN

Low-resistance, high-transparency, and thermally stable Ohmic contacts on p-type GaN were achieved using Ru and Ir. Oxidation annealing under O-2 atmosphere led to the reduction of contact resistivity by greater than one order of magnitude, compared to annealing under N-2. The bilayer contacts of Ru (50 Angstrom)/Ni (50 Angstrom) and Ir (50 Angstrom)/Ni (50 Angstrom) exhibited a low contact resistivity of similar to4x10(-5) Omega cm(2) and high light transmittance of similar to85% after annealing at 500 degreesC for 1 min under O-2. The barrier height for hole injection could decrease via contact formation of RuO2 (or IrO2) on p-type GaN. The Au-free contact structure of NiO/RuO2 (IrO2)/GaN led to high light transmittance and good thermal stability. (C) 2003 American Institute of Physics.