Fabrication of AlGaN/GaN Fin-Type HEMT using a novel t-gate process for improved radio-frequency performance

To increase the radio-frequency (RF) performance of AlGaN/GaN-based fin-type high electron mobility transistors (HEMTs), a novel T-gate process was developed and applied to fabricate a device with high RF performance. In a single lithography process, the applied T-gate process shows a technique for forming a T-gate using the reactivity difference of several photoresists. The fabricated device has a steep fin width (Wfin) of 130 nm, a fin height (Hfin) of 250 nm, and a gate length (LG) of 190 nm. The device exhibits a low leakage current (Ioff) of 6.6 × 10-10 A/mm and a high Ion/Ioff current ratio of 4.7 × 108. Moreover, the fabricated device achieved a high cut-off frequency (fT) of 9.7 GHz and a very high maximum oscillation frequency (fmax) of 27.8 GHz. The fmax value of the proposed device is 138% higher than that of GaN-based fin-type HEMTs without T-gate.