Positive Shift in Threshold Voltage Induced by CuO and NiOx Gate in AlGaN/GaN HEMTs

AlGaN/GaN HEMTs with two kinds of p-type metal-oxide (CuO and NiOx) gates have been fabricated, in which the threshold voltage can be modulated effectively. Especially, the threshold voltage of the device shows a 0.7 V positive shift with a high-quality CuO gate layer. Meanwhile, a high on/off current ratio of ~109, a large saturated drain current of ~1030 mA/mm, and an improved transconductance of 200 mS/mm are also achieved. The pulsed transfer characteristics and output characteristics exhibit small hysteresis and ignorable current collapse, signifying an excellent CuO/AlGaN interface. Therefore, CuO can be used as a potential p-type gate for high-performance GaN-based MIS-HEMTs.