Dependence of DC and RF characteristics on gate length for high current AlGaN/GaN HFETs

The fabrication and performance of AlGaN/GaN heterostructure field-effect transistors of various gale lengths are reported. The unity current gain cutoff frequency (f(t)), maximum frequency of oscillation (f(max)), and threshold voltage are investigated against gate length. The measured f(t) and f(max) values ranged from 37 and 81GHz to 11 and 31GHz for the 0.25 and 1 mu m gate length devices, respectively. These devices also exhibited drain currents as high as 1A/mm.