600 °C operation of MBE-enabled ScAlN/AlN/GaN FinHEMTs

We report Sc0.15Al0.85N/AlN/GaN fin high-electron-mobility transistors (FinHEMTs) with stable operation up to 600 °C, enabled by a nearly lattice-matched Sc0.15Al0.85N barrier grown by molecular beam epitaxy. The fin sidewalls provide additional electrostatic control, strengthening gate modulation and thereby reducing off-state current (Ioff) and gate leakage (IG), improving subthreshold swing (SS), and shifting the threshold voltage (VT) positively relative to planar devices. At room temperature, the FinHEMTs with a fin width (Wch) of 0.4 μm achieve an on/off current (Ion/Ioff) ratio of ∼107, an SS of ∼105 mV/dec, and an on-state current (Ion) of ∼330 mA/mm. The devices also exhibit strong thermal robustness, maintaining Ion of 110 mA/mm at a gate–source voltage (VGS) of 0 V and an Ion/Ioff ratio of 890 at 600 °C. These results establish ScAlN/AlN/GaN FinHEMTs as a promising platform for extreme-temperature electronics.