Improved performance of scaled AlGaN/GaN HFETs by recessed gate

Abstract

The performance of scaled AlGaN/GaN HFETs was significantly improved by using gate-recess technology and regrown n⁺-GaN Ohmic contacts. Source-to-drain distance (Zsd) was scaled to 600 nm by employing regrown n⁺-GaN Ohmic contacts. Low-damage gate recess was taken before 60 nm T-shaped gate metallization. The drain current curve becomes flat over knee voltage, and the short-channel effects were suppressed obviously after gate recessing. The peak transconductance (gm) increased from 607 mS/mm to 764 mS/mm. Moreover, after gate recessing, the value of maximum oscillation frequency (fmax) increases from 192 GHz to 263 GHz, while there is almost no decrease in the value of unity current gain cut-off frequency (fT). The devices with gate recess exhibit a record-high value of √fT·fmax in AlGaN/GaN HFETs. This indicates that the AlGaN/GaNHFETs still have the potential for D-band application with further optimization.