Ultrawide Bandgap Channel Polarization-Doped Junction Field-Effect Transistor

An ultrawide bandgap (UWBG) AlGaN channel polarization-doped junction field-effect transistor (POLJFET) grown by molecular beam epitaxy on a bulk AlN substrate is presented. The POLJFET leverages distributed polarization doping for the p-side gate, owing to the challenges associated with reliable acceptor impurity doping in UWBG AlGaN. Successful gate control of the transistor channel by pn junction field effect, with a threshold voltage of approximate to-30 V, is demonstrated. The transistor shows a significantly low OFF current (<10 nA mm(-1)) while the ON current is 0.03 mA mm(-1), primarily limited by the high contact resistivity of the n-type AlGaN channel. This is expected due to the low doping of n-AlGaN by design and can be mitigated by contact optimization techniques (either by regrowth or ion implantation) in future iterations.