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 (4×1017 cm−3). It is shown that the two-step surface-treated Rh contacts (10 nm) produce a specific contact resistance of 1.7×10−5 Ω cm2. It is also shown that the two-step treated Rh/Ni (5/5 nm) and Rh/Au (5/5 nm) contacts yield 6.0×10−5 and 9.3×10−6 Ω cm2, 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.