Formation mechanisms of low-resistance and thermally stable PdNiPdRu Ohmic contacts to Mg-doped Al0.15 Ga0.85 N

The authors report on the formation of low-resistance and thermally stable PdNiPdRu Ohmic contacts to Mg-doped AlGaN. The contacts become Ohmic with a contact resistivity of (1.4±0.3) × 10-5 cm2 upon annealing at 600 °C for 1 min in a N2 ambient. The samples do not experience significant degradation of the specific contact resistance and the surface roughness even after annealing at 600 °C for 60 min. Based on x-ray photoelectron spectroscopy depth profile results, atomic force microscopy, and contact resistivity-temperature data, possible Ohmic formation and carrier transport mechanisms are described and discussed.