Effect of Post Annealing on Electrical Properties of (Ni/Au)/Al0.20Ga0.80N Schottky Contacts

The effects of thermal annealing on the electrical properties of Ni/Au Schottky contacts on n-type AlxGa1-xN (x=0.20) were investigated by current-voltage (I-V) and capacitance-voltage (C-V) measurements. The Schottky barrier height (SBH) of as-deposited contacts was found to be 0.946±0.033 eV (from I-V) and 1.120±0.047 eV (from C-V) with an ideality factor of 1.655±0.137. The values of SBH obtained from the C-V measurements were found to be higher than that of obtained from the I-V measurements. This was attributed to the presence of the lateral inhomogeneities of the barrier height. The values of SBH slightly increased after the annealing temperatures at 300, 400 and 500 °C. The highest value of SBH for Ni/Au Schottky contact was obtained after annealing at 600 °C and the value was 1.521±0.032 eV. The good performance of the annealed Ni/Au contact can be attributed to reaction of Ni with the GaN cap layer of AlGaN substrate, and formation of intermetallic compounds such as GaNi and reduced interfacial defects at the metal/GaN interface.