Annealing effects on structural and electrical properties of Ru/Au on n-GaN Schottky contacts

Thermal annealing effects on electrical and structural properties of Ru/Au Schottky contact to n-type GaN (nd = 4.07 × 1017 cm−3) have been investigated using current–voltage (I–V), capacitance–voltage (C–V), Auger electron spectroscopy (AES) and X-ray diffraction (XRD). The Schottky barrier height of the as-deposited sample was found to be 0.75 eV (I–V) and 0.93 eV (C–V), respectively. It is noted that the barrier height increased when the contact was annealed at 300 °C and slightly decreased upon annealing at temperatures of 400 °C and 500 °C. The extracted Schottky barrier heights are 0.99 eV (I–V), 1.34 eV (C–V) for 300 °C, 0.88 eV (I–V), 1.20 eV (C–V) for 400 °C and 0.72 eV (I–V), 1.08 eV (C–V) for 500 °C annealed contacts, respectively. Further it is observed that annealing results in the improvement of electrical properties of Ru/Au Schottky contacts. Based on Auger electron spectroscopy and X-ray diffraction studies, the formation of gallide phases at the Ru/Au/n-GaN interface could be the reason for the improvement of electrical characteristics upon annealing at elevated temperatures.