Low-resistance and high-transparency Ni/indium tin oxide ohmic contacts top-type GaN

The characteristics of Ni/indium tin oxide (ITO) ohmic contacts to p-type G aN (similar to 2x10(17) cm(-3)) have been studied. The Ni/ITO (10 nm/250 nm ) layers were prepared by thermal evaporation and rf magnetron sputtering, respectively. Although the as-deposited Ni/ITO contacts present rectified b ehavior, the linear current-voltage characteristics can be obtained. The co ntact resistance can be reduced significantly for the ITO/Ni/p-GaN samples after suitable rapid thermal process. The contact property of ITO/Ni/p-GaN shows lowest specific contact resistivity of 8.6x10(-4) Omega cm(2) and hig h transparency (above 80% for 450-550 nm) as the sample annealed at 600 deg reesC in air. Possible mechanisms for the observed low contact resistance a nd high transparency will be discussed. The present process is compatible w ith the fabrication for the high-efficient GaN light-emitting devices. (C) 2001 American Institute of Physics.