Improvement of Gate Length Dependence in Electrical Characteristics of AlGaN/GaN Dual-Gate HEMTs

This article examines the impact of gate length (L-g) on the dc, pulsed I-V, and small-signal characteristics of dual-gate (DG) AlGaN/GaN high electron mobility transistors (HEMTs). T-shaped DG structures with gate lengths ranging from 0.1 to 0.3 mu m were fabricated using i-line stepper lithography and a thermal reflow technique. The short-channel effect was successfully eliminated in the DG devices, while single-gate (SG) devices fabricated on the same wafer were significantly affected by this phenomenon. The dependence of current collapse on L-g in the DG devices showed a reduction in the collapse by a factor of 5 or more compared to the SG devices. Further-more, a 120-nm DG-HEMT exhibited a 10-dB reduction in the isolation and an extrapolated maximum oscillation frequency of 239 GHz, whereas a 110-nm SG-HEMT exhibited that of 146 GHz.