Enhancement-mode N-polar GaN MOS-HFET with 5-nm GaN channel, 510-mS/mm g _m, and 0.66-Ω • mm R _on

We report enhanced dc and small-signal RF performance of enhancement-mode (E-mode) metal-oxide-semiconductor heterojunction field-effect transistors (MOS-HFETs) in N-polar GaN technology with an ultrathin 5-nm GaN channel and graded AlGaN back-barrier structure with a record on-resistance (R _on) of 0.66 Ω mm. The device has a maximum drain current (I _d) of 1.15 A/mm, a peak transconductance (g _m) of 510 mS/mm, and a peak current-gain cutoff frequency (f _t) of 122 GHz, with a positive threshold voltage (V _th) of 1.6 V. The device shows improved saturation and pinchoff characteristics compared to the previously reported N-polar E-mode HFETs with a maximum I _onrm _off ratio of 2.2 × 10 ⁵.