Temperature-dependent current-voltage characteristics of Al-doped Mg_xZn_1-xO/AlGaN n-p junction diodes

This study investigated the temperature dependence of the current-voltage (I-V) characteristics of Al-doped Mg_xZn_1-xO/p-AlGaN junction diodes. The n-type Al-doped Mg_xZn_1-xO (AMZO) films were deposited on p-AlGaN using a radio-frequency (rf) magnetron sputtering system followed by annealing at 700, 800, and 900°C in a nitrogen ambient for 60 s. The n-AMZO/p-AlGaN diode at a substrate temperature of 25°C showed the lowest leakage current in reverse bias. The n-AMZO/p-AlGaN diode with an AMZO annealed at 900°C demonstrated the lowest reverse leakage current. The temperature sensitivity coefficients of the I-V characterizations were obtained at different substrate temperatures (25, 50, 75 100, and 125°C), providing extracted values of 6.4, 7.6, and 5.6 mV/°C in forward bias and -20, 5.6, and 0.8 mV/°C in reverse bias for the AMZO films annealed at 700, 800, and 900°C, respectively. The n-AMZO/p-AlGaN junction diode fabricated with AMZO annealed at 900°C demonstrated the lowest temperature dependence. In addition, the light emission was derived from the forward-biased junction, and near-ultraviolet light emission was evident at all of the p-n diodes. Based on these findings, the n-AMZO/p-AlGaN diodes are suitable for GaN-based heterojunction bipolar transistors (HBTs) and near-ultraviolet light-emitting diodes (LEDs).