Study on the frequency characteristics of split-gate AlGaN/GaN HFETs

In this study, we report on the direct-current (DC) and frequency characteristics of split-gate heterostructure field-effect transistors (HFETs) with different split-gate lengths. The split-gate HFET contains two distinct operating parts, the large and the small transconductance parts. The split-gate HFET has a current cutoff frequency ([Formula: see text]) of 814[Formula: see text]MHz and a maximum oscillation frequency ([Formula: see text]) of 18.8[Formula: see text]GHz in the large transconductance part. Meanwhile, in the small transconductance part, there is a higher unilateral power gain of [Formula: see text][Formula: see text]GHz. Also, the split-gate HFET exhibits a voltage gain greater than 1 (0[Formula: see text]dB) at both DC and frequencies. Additionally, compared to the large transconductance part, the small transconductance part of the split-gate HFET presents a 53.5% reduction in DC power consumption and a larger input signal voltage range. Split-gate HFETs can be used as conventional power amplifiers in the large transconductance part and are also suitable as low-power voltage amplifiers in the small transconductance part.