Characterization of 0.18-μm gate length AlGaN/GaN HEMTs on SiC fabricated using two-step gate recessing

Abstract

We fabricated a 0.18-μm gate-length AlGaN/GaN high electron mobility transistor (HEMT) on SiC substrate fabricated by using two-step gate recessing which was composed of inductively coupled plasma (ICP) dry etching with a gas mixture of BCl3/Cl2 and wet chemical etching using the oxygen plasma treatment and HCl-based cleaning. The two-step gate recessing process exhibited an etch depth of 4.5 nm for the AlGaN layer and the clean surface of AlGaN layer at the AlGaN/gate metal contact region for the AlGaN/GaN HEMT structure. The recessed 0.18 μm × 200 μm AlGaN/GaN HEMT devices showed good DC characteristics, having a good Schottky diode ideality factor of 1.25, an extrinsic transconductance (g _m ) of 345 mS/mm, and a threshold voltage (V _th ) of −2.03 V. The recessed HEMT devices exhibited high RF performance, having a cut-off frequency (f _T ) of 48 GHz and a maximum oscillation frequency (f _max ) of 130 GHz. These devices also showed minimum noise figure of 0.83 dB and associated gain of 12.2 dB at 10 GHz.