In this paper, we report on 1.2-kV-class vertical GaN-based trench metal–oxide–semiconductor field-effect transistors (MOSFETs) on a free-standing GaN substrate with a low specific on-resistance. A redesigned epitaxial layer structure following our previous work with a regular hexagonal trench gate layout enables us to reduce the specific on-resistance to as low as 1.8 mΩ·cm2 while obtaining a sufficient blocking voltage for 1.2-kV-class operation. Normally-off operation with a threshold voltage of 3.5 V is also demonstrated. To the best of our knowledge, this is the first report on vertical GaN-based MOSFETs with a specific on-resistance of less than 2 mΩ·cm2.

This paper reports the characteristics of vertical GaN-based trench metal-oxide-semiconductor field-effect transistors on a free-standing GaN substrate with a blocking voltage of 1.6 kV. The high blocking voltage was obtained by using field plate edge termination around the isolation mesa of the transistor. To our knowledge, the blocking voltage is the highest ever reported for vertical GaN-based transistors on free-standing GaN substrates. Normally off operation with a threshold voltage of 7 V is also demonstrated.

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