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 ≈−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.