Threshold voltage control with high temperature gate-oxide annealing in ultrawide bandgap AlGaN-channel MOSHFETs

Abstract We report threshold voltage (VTH) control in UWBG Al0.4Ga0.6N-channel metal oxide semiconductor heterostructure field effect transistors (MOSHFETs) using a high-temperature (300 °C) anneal of the high-k ZrO2 gate-insulator. Annealing switched the polarity of the fixed charges at the ZrO2/AlGaN interface from +5.5×1013 cm-2 to -4.2×1013 cm-2, pinning VTH at ~ (-12V), reducing gate leakage by ~103, and improving subthreshold swing 2x (116 mV/decade). It also enabled the gate to repeatedly withstand voltages from -40 V to +18 V, allowing the channel to be overdriven doubling the peak currents to ~0.5A/mm.