High-temperature characteristics of Al_xGa_1-xN-based vertical conducting diodes

We investigated the high-temperature characteristics for Al _xGa_1-xN-based (x = 0-0.57) vertical conducting diodes. In the forward current-voltage (I-V) characteristics, the offset voltage decreases with temperature because of the reduction of the built-in potential due to the decrease in the bandgap energy with temperature. In spite of an increase in SiC substrate resistance with temperature because of a decrease in the electron mobility, the on-state resistance of the diode with Al_0.22Ga _0.78N is as low as 1.45mΩcm² even at 250°C because of the reduced resistance of the p-InGaN layer due to an increase in the hole concentration. In the reverse I-V characteristics, the breakdown voltage increases with increasing Al composition, x, of Al_xGa_1-xN layer because the higher the Al composition of the Al_xGa _1-xN layer is, the higher the critical electric field becomes. Although the reverse leakage current of Al_xGa_1-xN-based diodes increases with increasing temperature, the breakdown voltage at elevated temperatures is similar to that at room temperature. These features indicate the feasibility of Al_xGa_1-xN-based diodes for high-temperature operation.