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We report threshold voltage (V_TH) control in ultrawide bandgap Al_0.4Ga_0.6N-channel metal oxide semiconductor heterostructure field-effect transistors using a high-temperature (300 °C) anneal of the high-kZrO₂gate-insulator. Annealing switched the polarity of the fixed charges at the ZrO₂/AlGaN interface from +5.5 × 10¹³cm⁻²to −4.2 × 10¹³cm⁻², pinningV_THat ∼ (−12 V), reducing gate leakage by ∼10³, and improving subthreshold swing 2× (116 mV decade⁻¹). It also enabled the gate to repeatedly withstand voltages from −40 to +18 V, allowing the channel to be overdriven doubling the peak currents to ∼0.5 A mm⁻¹.

 

Abstract We demonstrate fully fabricated AlGaN/GaN high electron mobility transistors (HEMTs) transferred from sapphire to copper tape on flexible polyethylene terephthalate using 193 nm excimer laser liftoff (LLO). The heterojunction is structurally intact after LLO, leading to preserved electron mobility μ n ∼1630 cm 2 V −1 s −1 and carrier concentration n s ∼10 13 cm −2 . The maximum drain saturation current decreased by ∼18% after transfer, which is a lower reduction than other reported transfer methods. The drain current of this flexible HEMT increased monotonically under tensile stress applied using a convex-shaped plate, while the threshold voltage shifted more negative in quantitative agreement with the expected piezoelectric charge for an intact heterojunction.