(388f) Extreme Temperature Operation of Ultra-Wide Bandgap AlGaN Polarization-Doped Field Effect Transistors

Ultra-wide bandgap semiconductors provide an attractive future for power electronics due to the ability to withstand high power densities and withstand high critical electric fields. Polarization-doped field effect transistors (POLFETs) were fabricated with an unintentionally doped Al_xGa_1-xN channel layer graded from Aluminum compositions of 0.7 to 0.85 with planar Ohmic contacts to the Al_0.85Ga_0.15N surface. DC and pulsed characterization were performed from room temperature to 500°C in ambient. DC current-voltage characteristics demonstrated only a 70% reduction in On-state current from 25 to 500°C and the full ability to modulate current via the gate at all temperatures. Ideal switching characteristics via gate lag were realized across the entirety of the temperature range. The ability for operation at high temperature is enabled by an unpinned Ni/Au Schottky gate contact, such that the barrier height increases with temperature from 2.05 eV to 2.76 eV at 25 and 500°C, respectively. The high barrier height lead to an excellent I_on/I_off ratio of 1.5 × 10⁹ at room temperature.