Proton Damage Effects in Double Polymorph γ/β-Ga2O3 Diodes

Double polymorph γ/β-Ga2O3 structures remain crystalline upon unprecedentedly high crystal disorder levels where other semiconductors lose their long-range symmetry and, eventually, become amorphous. However, it is unclear if this radiation tolerance translates to device-like operation, where much lower levels of damage degrade the performance. In this work, we fabricated conducting double polymorph γ/β-Ga2O3 structures using ion implantation and subsequent hydrogenation of the top γ-Ga2O3 layer, instead of conventional impurity doping which is limited by γ-Ga2O3 stability tradeoffs. While not a direct comparison, these structures exhibited much higher radiation tolerance compared to conventional Schottky diodes made of β-Ga2O3. Specifically, using 1.1 MeV proton irradiation at fluences of 1014–1015 cm−2, conventional β-Ga2O3 diodes became unfunctional, while double polymorph γ/β-Ga2O3 diodes remained operational. The centers supplying electrons in γ-Ga2O3 were characterized by prominent DX-like persistent photocapacitance. For samples implanted with Ga+ and Si+ to produce the β → γ transition, annealed at 600 °C and plasma hydrogenated, the net donor concentration was ∼1012 cm−3, with dominant electron traps near EC − 0.65–0.7 eV and photocapacitance and photocurrent spectra determined by deep acceptors with optical ionization thresholds 1.3 eV, 2 eV, 2.3 eV and 2.8 eV. Irradiation with 1 MeV protons increased the net donor density of these conducting γ/β-Ga2O3 structures, with carrier creation rates of (1.5–4.4) × 10−2 cm−2, in sharp contrast to the carrier removal rates of 150–200 cm−1 under identical conditions in the original β-Ga2O3 films.