Characterization of 0.18-㎛ Gate Length AlGaN/GaN HEMTs on SiC Fabricated Using Two-Step Gate Recessing

We fabricated a $0.18-{\mu}m$ 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 $BCl_3/Cl_2$ 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 $0.18{\mu}m{\times}200{\mu}m$ 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.