Ultra-wide band gap AlGaN polarization-doped field effect transistor

Polarization-doped field effect transistors (PolFETs) were realized with an unintentionally doped AlxGa1−xN channel layer graded over Al compositions 0.70 ≤ x ≤ 0.85 and ohmic contact formation to the Al0.85Ga0.15N surface. Current density of 24 mA/mm was attained for a modest threshold voltage of −3.95 V owing to the high sheet charge concentration (ns) of 5.4 × 1012 cm−2 and average electron mobility (μ) of 210 cm2 V−1 s−1 for the channel region along with ohmic contacts with a specific contact resistivity of 1.1 mΩ cm2 and a large Schottky barrier height of 3.0 eV for the metal–semiconductor gate. The combination of ultra-wide band gap energy, high μ, and high ns, linear ohmic contacts, and large Schottky barrier for AlGaN PolFETs makes them attractive for both high voltage switches and high power rf devices.