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 $\hbox{Al}_{2}\hbox{O}_{3}$/InAlN/GaN metal–oxide–semiconductor HFETs (MOSHFETs) with varied gate length was evaluated. The current gain cutoff frequency $f_{T}$ and the maximum oscillation frequency $f_{\max}$ for the HFETs with 0.3- $\mu\hbox{m}$ gate length were 54 and 58 GHz, respectively. An increase of $f_{T}$ to 61 GHz and of $f_{ \max}$ to 70 GHz was obtained for the MOSHFETs. The HFETs and MOSHFETs with different gate length yielded an $f_{T} \times L_{G}$ product of 18 and 21 $\hbox{GHz}\cdot\mu\hbox{m}$, respectively. These are higher values than reported yet on InAlN/GaN devices and similar to those known for AlGaN/GaN HFETs.