The effect of Al and Pt/Ti simultaneously annealing on electrical characteristics of n-GaN schottky diode

Wideband gap semiconductor GaN has received increasing attention for its potential for wide variety of high-power, high-performance switching and high-frequency devices application. In this pap er the simultaneous annealing effect at a temperature of 400 degrees C similar to 700 degrees C in N-2 ambient for 12min on Aluminum (1500A degrees) as an ohmic contact while Pt/Ti (700A degrees/700A degrees) bilayer as a Schottky contact on the electrical characteristics of nGaN Schottky diode was investigated. It was found that at a annealing temperature of 400 degrees C produced the best (I-V) characteristics, barrier height (phi(B)) 1.1eV, ideality factor (eta) 1.1 as compared to the other annealing temperature. The (C-V) characteristics of n-GaN Schottky diode were measured at 100 kHz and I MHz frequency at different annealing temperature. It was found that at annealing temperature of 400 degrees C, the depletion region is maximum with the capacitance value varied from 0.02pF similar to 0.04pF. At low frequency 100 kHz the capacitance increase with increasing forward voltage which is frequency independent, while at high frequency]MHz the capacitance-voltage curve is almost flat. The surface morphology of n-GaN Schottky diode before annealing and after annealing was observed by SEM, XRD. It was found that Al (1500A degrees) didn't show any significant loss of dimensional stability at annealing temperature 400 degrees C similar to 700 degrees C, while Pt/Ti (700A degrees/700/A degrees) show balling effect, surface morphology degradation at above 400 degrees C which was confirmed by XRD measurement. Hence we conclude that rectifying behavior of n-GaN schottky diode was observed at annealing temperature 4000C while annealing at above 400 degrees C similar to 700 degrees C the rectifying characteristics of n-GaN schottky diode changed to ohmic behavior due to Pt/Ti (700A degrees/700A degrees) island form. of surface morphology occurred, while Al (1500A degrees) as a ohmic contact show thermal stability at high temperature. annealing above 400 degrees C of n-GaN Schottky diode.