Normally-off operation of Al2O3/GaN MOSFET based on AlGaN/GaN heterostructure with p-GaN buffer layer

An AlGaN/GaN-based normally-off GaN MOSFET with p-GaN buffer layer has been demonstrated, for the first time, using over-recessed gate. It is believed that p-GaN buffer layer has advantage of not only increasing the threshold voltage due to depletion effect, but also reducing the buffer leakage current. The fabricated GaN MOSFET with 30 nm-thick ALD Al₂O₃ as the gate insulator exhibited good device performances, such as a maximum drain current of 109 mA/mm, a maximum extrinsic transconductance of 30 mS/mm, a low specific on-resistance of 1.86 mΩ·cm², and a subthreshold slope of 365 mV/dec with threshold voltage of 2.9 V.