Power Scaling of Graded-Channel GaN HEMTs With Mini-Field-Plate T-gate and 156 GHz fT

We report 60-nm gate-length graded-channel AlGaN/GaN HEMTs fabricated with a mini-field-plate T-gate. The devices exhibit an extrinsic f
_T
and f
_MAX
of 156 GHz and 308 GHz, respectively. At 60-nm gate length, the f
_T
*Lg of 9.4 GHz *μm is comparable to that of conventional scaled short gate-length AlGaN/GaN HEMTs. Due to minimal current collapse, the graded-channel GaN HEMTs demonstrated linear RF power scaling up to 5.5 W/mm at 30 GHz. This results in a record f
_T
* power density product of 858 GHz * W/mm for Ga-polar GaN devices, indicating the promise of this device architecture for mmW amplifiers.