Ultrahigh Breakdown Field of Ga₂O₃ Film with Single Layer via Novel Aerosol Deposition Process

Power semiconductor devices are vital in modern electronic systems such as electric vehicles, renewable energy systems, and high-power electronics, enabling efficient power management and conversion. Key parameters for power switches, including Baliga’s figure of merit (BFOM), Huang’s material figure of merit (HMFOM), Johnson’s figure of merit (JFOM), switching frequency, and on-field resistance, are essential for achieving low losses and reliable switching at high voltages.
A higher breakdown field (E_c) is crucial for improving BFOM (~E_c³), HMFOM (~E_c), JFOM (~E_c), and on-field resistance. Wide-bandgap materials such as GaN and SiC have been used for power-switch applications due to their high breakdown fields. However, ultrawide-bandgap materials, particularly β-gallium oxide (Ga₂O₃), are emerging as promising candidates for next-generation power-switch devices because of their large bandgap (4.9 eV) and theoretical breakdown field of 8 MV/cm. Ga₂O₃ also offers cost-effective, large-scale production with low defect density.
Recent research on Ga₂O₃ power devices has focused on Schottky barrier diodes (SBDs) and metal–oxide–semiconductor field-effect transistors (MOSFETs). For instance, Dhara et al. enhanced the breakdown field of Ga₂O₃ SBD from 2.2 MV/cm to 4.1 MV/cm through field termination [1]. Yan et al. achieved a breakdown field of 5.2 MV/cm using a Ga₂O₃/graphene heterostructure [2]. However, these devices still fall short of the theoretical 8 MV/cm breakdown field, despite their complex structures.
Common fabrication methods for Ga₂O₃ films include metal organic chemical vapor deposition, pulsed laser deposition, molecular beam epitaxy, and atomic layer deposition. These processes typically require high temperatures, are costly, and involve long growth times. In contrast, aerosol deposition (AD), a room-temperature, powder-impact coating technique, can overcome these limitations. AD is fast, creates dense films with strong adhesion, and functions in low-vacuum environments. It also improves surface roughness and internal density with a simple nozzle-tilting method.
Despite these advantages, research on AD for Ga₂O₃ power semiconductors remains limited. A previous study on Ga₂O₃ film fabrication using AD achieved a deposition rate of 460 nm/min and a film thickness of 3 μm [3]. While this film exhibited a dense structure and low leakage current, the breakdown field remained low (~1 MV/cm), likely due to high surface roughness and a high density of oxygen vacancies. Oxygen-vacancy defects in Ga₂O₃ significantly affect its electrical and structural properties, including electrical conductivity and bandgap reduction. Many studies have shown that increasing oxygen vacancies enlarge electrical conductivity and reduces the bandgap [4]. However, there is a lack of quantitative research on the relationship between oxygen vacancies and breakdown fields.
This study addresses these challenges by employing thickness optimization, post-annealing, and the nozzle-tilting method to fabricate Ga₂O₃ films using AD for high-power semiconductors. The films were produced in dielectric structures with varying thicknesses to achieve a high breakdown field with minimal film thickness. Post-annealing reduced the oxygen vacancy density, and the nozzle-tilting method improved surface roughness and film density. Consequently, the Ga₂O₃ film achieved a high breakdown field of 5.5 MV/cm, the highest recorded for a single dielectric layer without passivation or field termination. This suggests that AD-manufactured Ga₂O₃ films could be viable for producing cost-effective, reliable power switches like SBDs and MOSFETs, with low on-resistance, minimal losses, and high-voltage switching capabilities.
Reference
[1] S. Dhara et al., Appl. Phys. Lett. 2022, 121, 203501.
[2] X. Yan et al., Appl. Phys. Lett. 2018, 112, 032101.
[3] J.W. Lee et al., Ceram. Int. 2024, 50, 14067.
[4] T. Kang et al., J. Alloys Compd. 2022, 926, 166887.