Proton irradiation effects on GaN-based high electron-mobility transistors with Si-doped AlxGa1-xN and thick GaN cap Layers

1.8 MeV proton radiation-induced degradation in high electron mobility transistors with Si-doped Al_xGa_1-xN and thick GaN cap layers is studied up to a fluence of 1×10¹⁵ protons/cm². The thick GaN cap layer reduces sheet charge modulation induced by the surface states, as it electrostatically separates the active device layers from the surface, thereby enhancing the device performance. The devices exhibit good tolerance up to 10¹⁴ protons/cm², with displacement damage being the primary degradation mechanism. Charged defect centers introduced by proton radiation in the active device layers degrade carrier mobility and sheet carrier density. Proton radiation alters the barrier height at the Schottky gate and increases the resistance of the thin film structure.