Investigation of metal-insulator-semiconductor diode with alpha-Ga2O3 insulating layer by liquid phase deposition

Highlights: • α-Ga₂O₃ thin films were synthesized by liquid phase deposition with annealing. • α-Ga₂O₃ thin films are uniform and dense. • Ni/α-Ga₂O₃/Si diode exhibits a current density of 1.07 × 10⁻⁵ A/cm² at −2 V. -- Abstract: We report a metal-insulator-semiconductor (MIS) diode with an α-Ga₂O₃ thin-film insulator layer grown by liquid-phase deposition (LPD). α-Ga₂O₃ exhibits a high energy bandgap of 4.9–5.3 eV, which can effectively reduce the leakage current density and improve the breakdown voltage of the diode. The α-Ga₂O₃ thin films are synthesized from GaOOH with LPD. The α-GaOOH crystal is simply obtained by the dissociation of the Ga(OH)₃ precursor solution. GaOOH can be transformed into α-Ga₂O₃ crystal and form a uniform thin film following post-growth annealing. When the α-Ga₂O₃ thin film is inserted in between Ni and Si to form a Ni/α-Ga₂O₃/Si MIS diode, the barrier height of the diode increases by 0.4 eV and the on/off ratio by 100-fold from those of the Ni/Si Schottky diode. The Ni/α-Ga₂O₃/Si MIS diode exhibits a leakage current density of 1.07 × 10⁻⁵A/cm² under −2 V bias. The breakdown voltage of the diode reaches −166 V without the guard ring and other insulation structures. Our results demonstrate that LPD-grown α-Ga₂O₃ thin films can obtain uniform and dense structure under short deposition time and at an annealing temperature of 400 °C. The uniform insulating layer of α-Ga₂O₃ has a high potential in enhancing the electrical characteristic of diodes and other power electronic devices.