High-quality nonalloyed rhodium-based ohmic contacts to p-type GaN

We report on a promising Rh-based scheme for high-quality ohmic contacts to surface-treated p-GaN:Mg (4x10(17) cm(-3)). It is shown that the two-step surface-treated Rh contacts (10 nm) produce a specific contact resistance of 1.7x10(-5) Omega cm(2). It is also shown that the two-step treated Rh/Ni (5/5 nm) and Rh/Au (5/5 nm) contacts yield 6.0x10(-5) and 9.3x10(-6) Omega cm(2), respectively. Based on the current-voltage measurement, x-ray photoemission spectroscopy, and Auger electron spectroscopy results, the mechanisms for the formation of the nonalloyed Rh-based ohmic contacts is described and discussed. (C) 2003 American Institute of Physics.