Normally-off AlGaN/GaN HFETs using NiO<inf>x</inf> gate with recess

Abstract

The normally-off AlGaN/GaN HFETs on Si substrate were fabricated. To realize normally-off characteristic, recess was formed under the gate electrode and NiOx was formed as a gate electrode. As a result, the fabricated AlGaN/GaN HFET with a gate width of 157 mm exhibited a threshold voltage of +0.8 V, a breakdown voltage of more than 800 V, an on-resistance of 72 mΩ, and a maximum drain current of more than 20 A. The on-resistance-area product (Ron×A) was 0.28 Ω· mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . This value is approximately 1/28 compared with that of conventional Si MOSFETs. The gate leakage current was decreased about four orders of magnitude smaller than the conventional normally-on HFETs. The NiOx gate electrode operates as a p-type material.