Al Ga N ∕ Ga N ∕ Al N quantum-well field-effect transistors with highly resistive AlN epilayers

Al Ga N ∕ Ga N ∕ Al N quantum-well field-effect transistors have been demonstrated. By replacing a semi-insulating GaN epilayer with a highly resistive AlN epilayer in the device structure, parasitic conduction in the GaN epilayer, leakage current through the GaN epilayer, and the channel electrons spillover into the GaN epilayer have been completely eliminated and the drain current collapse has been reduced. The fabricated devices on sapphire substrate with 1μm gate length show a high saturation current (>1A∕mm), and excellent gate control capability with a pinch-off voltage of −6V. Even without passivation, the devices exhibit small drain current collapse (<10%) under 1μs pulse gate driving.