A high-power AlGaN/GaN heterojunction field-effect transistor

Abstract

We fabricated an AlGaN/GaN heterojunction field effect transistor (HFET) with a very low on-state resistance. An undoped Al 0.2Ga 0.8N(30 nm)/GaN(2 μm) heterostructure was grown on a sapphire substrate using gas-source molecular-beam epitaxy. The undoped GaN layer had a high resistivity (above 10 M Ω ) and the breakdown field of the undoped layer was about 2 MV/cm. Si-doped GaN with a carrier concentration of 5×10 19 cm −3 was selectively grown in the source and drain regions for obtaining a very low contact resistance. As a result, a very low ohmic below 1×10 −7 Ω cm 2 was obtained. After that, an Al 0.2Ga 0.8N/GaN HFET was fabricated. The gate width was 20 cm and the gate length was 2 μm. The ohmic electrode materials were Al/Ti/Au and the Schottky electrodes were Pt/Au. The distance between the source and the drain was 13 μm. The HFET was operated at a current of over 20 A. A higher switching speed of HFET was obtained.