Effects of annealing on Ti, Pd, and Ni/n-Al_0.11Ga_0.89N Schottky diodes

Schottky diodes of Ti, Pd, and Ni/n-Al_0.11Ga_0.89N have been fabricated and the barrier heights were measured to be 0.60, 0.95 and 0.97 eV using current-voltage (I-V) measurements and to be 0.67, 1.15 and 1.22 eV using capacitance-voltage (C-V) measurements. Annealed Schottky diodes are showing higher I-V and C-V barrier heights when compared with as-deposited Schottky diodes except high temperature annealed (450°C/30 min-500°C/1 hr) Ti Schottky diodes. I-V barrier height of Ti/n-Al_0.11Ga_0.89N increases up to the annealing temperature 350°C/5 min and it decreased for higher annealing temperatures. C-V barrier height increases up to the annealing temperature 150°C/5 min for Ti (1.63 eV), 250°C/5 min for both Pd (1.68 eV) and Ni (1.54 eV) Schottky diodes respectively. The increase of barrier heights for low temperature annealing is due to intimate contact between metal and semiconductor. Rectifying behavior has been observed up to the annealing temperature 450°C/1 hr for Ni/n-Al_0.11Ga_0.89N and 500°C/1 hr for both Ti and Pd/n-Al_0.11Ga_0.89N Schottky diodes. An increase of surface average roughness has been observed for the annealed Pd and Ni Schottky diodes except Ti Schottky diodes. Al_0.11Ga_0.89N surface behaves more like ceramic with both Pd and Ni than semiconductor.