Interface engineering for minimizing trapped charge density in β-Ga₂O₃ Schottky barrier diodes for high-performance power devices

Abstract

Gallium oxide (Ga₂O₃), with its ultra-wide bandgap and high breakdown voltage, has emerged as a leading candidate for next-generation power devices. The performance and the Baliga figure-of-merit for power devices critically depend on breakdown voltage sustained by Schottky contact of metal with ultra-wide gap materials. However, high-quality Schottky contacts with Ga₂O₃ presents a significant challenge due to the presence of surface defects and formation of metal induced mid-gap defects states in Ga₂O₃. In this study, we investigate the electrical properties and defects at the interface between Ni metal and β-Ga₂O₃ thin films. Additionally, a 20 nm MgO thin films with various oxygen contents were deposited on β-Ga₂O₃ using radio-frequency magnetron sputtering and Ni/MgO/β-Ga₂O₃ metal-insulator-semiconductor Schottky diodes were fabricated. The frequency dependent C-V characteristic and surface-sensitive XPS depth profile is employed to study the interface of Ni/Ga₂O₃ and Ni/MgO/Ga₂O₃ Schottky barrier diodes. Our results show that the Ni/MgO/Ga₂O₃ Schottky barrier diode with 66 % O₂ in the MgO thin film during synthesis attains a barrier height of 0.87 eV. Subsequent post-metallization annealing at 300 °C in an Ar ambient for 30 min enhances the barrier height up to 1.1 eV. Also, a reduced on-resistance of 11.65 mΩ cm² and a lower on-voltage of 0.3V was obtained after annealing in Ar. The frequency dependent C-V characteristic results show no dispersion in capacitance for the annealed sample which signify the passivation of interface defects density (Δ_ιτ) and oxide charges density (N_f) in the dielectric layer (MgO). The minimum value of D_it and N_f achieved for the sample having highest barrier height (1.1eV) are 5.41 × 10¹¹/eV/cm² and 2.91 × 10¹⁰/cm³, respectively. This study establishes a vigorous foundation for the expanded utilization of Ga₂O₃ in power electronics devices, emphasizing the vital role of interface engineering.