Role of graphene interlayers in mitigating degradation of Ni/Au ohmic contact morphology on p-type GaN

摘要: Abstract We report an investigation of the effect graphene interlayers in maintaining good surface morphology low resistance Ni/Au Ohmic contacts to p -GaN (∼10 18  cm −3 ) annealed at 600 °C. Two different thin-film contact metallizations were compared, namely 20 nm Ni/200 nm Au with and without a layer diffusion barrier placed between metals. Raman spectroscopy measured several spots indicated single graphene, but subsequent transmission electron microscopy that more generally was nm thick. The unannealed showed specific resistances 2.1 × 10 −5  Ω-cm 2 3.1 × 10 −4 for Ni/Graphene/Au, respectively. After rapid thermal annealing 600 °C 60 s flowing N ambient, X-Ray Photoelectron Spectroscopy cross-sectional Transmission Electron Microscopy usual interchange occurred samples graphene. By sharp contrast, insertion prevented nickel gold up dramatically improved morphological stability metallization stack. results may be beneficial optoelectronic devices which reflectivity is critical.