RF Performance of InAlN/GaN HFETs and MOSHFETs With $f_{T} \times L_{G}$ up to 21 $\hbox{GHz}\cdot \mu\hbox{m}$

The RF performance of lattice-matched InAlN/GaN heterostructure field-effect transistors (HFETs) and Al₂O₃/InAlN/GaN metal-oxide-semiconductor HFETs (MOSHFETs) with varied gate length was evaluated. The current gain cutoff frequency fT and the maximum oscillation frequency f _max for the HFETs with 0.3-μm gate length were 54 and 58 GHz, respectively. An increase of fT to 61 GHz and off _max to 70 GHz was obtained for the MOSHFETs. The HFETs and MOSHFETs with different gate length yielded an fT ? LG product of 18 and 21 GHz ? μm, respectively. These are higher values than reported yet on InAlN/GaN devices and similar to those known for AlGaN/GaN HFETs.