Improved performance of scaled AlGaN/GaN HFETs by recessed gate

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 (Z
_sd
) 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 (g
_m
) increased from 607 mS/mm to 764 mS/mm. Moreover, after gate recessing, the value of maximum oscillation frequency (f
_max
) increases from 192 GHz to 263 GHz, while there is almost no decrease in the value of unity current gain cut-off frequency (f
_T
). The devices with gate recess exhibit a record-high value of √f
_T
·f
_max
in AlGaN/GaN HFETs. This indicates that the AlGaN/GaNHFETs still have the potential for D-band application with further optimization.