【Member Papers】Multi-fin normally-off β-Ga₂O₃ vertical transistor with a breakdown voltage exceeding 10 kV

      Researchers from the Novel Crystal Technology have published a dissertation titled "Multi-fin normally-off β-Ga₂O₃ vertical transistor with a breakdown voltage exceeding 10 kV" in Applied Physics Express.

Background

      β-Ga₂O₃ has attracted significant attention in power electronics, particularly for electric vehicles, power conditioning, and high-voltage switching applications, due to its large bandgap (4.5–4.9 eV), high theoretical breakdown field (6–8 MV/cm), and excellent Baliga’s figure of merit. Both lateral and vertical transistors have been developed; however, high-voltage vertical transistors face fabrication challenges, requiring high-quality, low-donor-concentration (≤5×10¹⁵ cm⁻³), thick epitaxial layers (≥50 µm), and effective edge-termination structures, with Cl incorporation being problematic in (001)-oriented layers. Recently, low-donor-concentration thick epitaxial layers have been achieved on (011) substrates, enabling the fabrication of high-voltage vertical transistors. In this work, multi-fin β-Ga₂O₃ vertical transistors were fabricated on such (011) epitaxial wafers, exhibiting normally-off behavior and a breakdown voltage exceeding 10 kV, demonstrating the potential of β-Ga₂O₃ vertical power devices for ultra-high-voltage applications.

Abstract

      We demonstrated a multi-fin normally-off β-Ga₂O₃ vertical transistor with a breakdown voltage exceeding 10 kV, specific on-resistance of 289 mΩ·cm², and power figure-of-merit of 0.35 GW/cm². The vertical transistor was fabricated on a low-donor-concentration (N_d-N_a≈ 1.8×10¹⁵ cm^-3) and thick (thickness≈ 85 µm) epitaxial layer grown on a (011) β-Ga₂O₃ substrate by halide vapor phase epitaxy to enhance the breakdown voltage. The breakdown voltage exceeding 10 kV is the highest reported for β-Ga₂O₃ vertical transistors. This result indicates the great potential of Ga₂O₃ vertical power devices.