Effect of post anode annealing on W/Au and Ni/Au multi-channel AlGaN/GaN Schottky diode

In this paper, multi-channel AlGaN/GaN Schottky diodes (MC-SBDs) with W/Au and Ni/Au anode metal were fabricated on the Si substrates, and the effect of post anode annealing (PAA) was investigated. The temperature of PAA varies from 300 °C to 550 °C. Benefitting from the multi-channel structure, low on-resistance (RON) of 3.11 Ω mm are obtained for Ni and W after 300 °C PAA. Meanwhile, the onset voltage (VON) of W is 0.34 V, much lower than 0.71 V for Ni. With PAA temperature rising, the VON and barrier height (φb) increase for both metals at the beginning because of the repair of etching damage. However, these parameters will decrease when the temperature exceeds the optimal value due to the deterioration of the Schottky interface. Correspondingly, the reverse current (IREV) drops first and then rises. The optimal PAA temperature is 450 °C for Ni and 500 °C for W. Furthermore, the temperature-dependent characteristics are also measured for comprehensive evaluation. The results show that the PAA has little effect on temperature-dependent forward characteristics for both Ni and W. However, the PAA can improve the high-temperature stability of IREV for Ni, whereas this advantage has not been observed on W, which is related to different leakage current mechanisms.