Trap-induced degradation mechanisms in quasi-vertical GaN PiN diodes under the combined effects of high-energy heavy ion irradiation and off-state reverse bias

Abstract

Wide-bandgap GaN power rectifiers hold promise for space electronic systems, particularly as freewheeling diodes in low-voltage secondary power supplies, yet their susceptibility to high-energy heavy ion irradiation remains largely unexplored. In this study, an irradiation-hardened quasi-vertical GaN PiN diode with a beveled-mesa termination structure is fabricated, exhibiting only an 8% reduction in blocking voltage under 1.3 GeV Ta ion irradiation with a high fluence of ∼107 ions/cm2. This robustness enables in-depth analysis of electrical degradation under the synergistic effects of irradiation and bias voltage. Forward I–V analysis reveals reductions in minority carrier lifetime, mobility, and diffusion length. Temperature-dependent reverse I–V characteristics show an upward shift in the transition voltage from variable range hopping leakage to space-charge-limited current conduction in irradiated devices, with additional involvement of trap-assisted Poole–Frenkel emission. deep-level transient spectroscopy identifies a shallow trap E2 (EC − 0.1 eV) and two deep traps, E1 (EC − 0.43 eV) and H1 (Ev + 0.68 eV). E1 exhibits a twofold increase in trap density post-irradiation and is attributed to dislocation-related defects or Ga vacancies. H1 likely originates from dissociation of Mg–H complexes under irradiation, forming MgGa and related complexes such as MgGa-VN. These traps, driven by the high electronic energy loss, could introduce localized recombination centers and scattering sites. These results offer critical insights into the irradiation-induced degradation mechanisms and design strategies for GaN-based power diodes (e.g., PiN diodes and Schottky diodes) and high electron mobility transistors in aerospace electronic systems.