Enhancement-Mode Pseudomorphic $\hbox{In}_{0.22} \hbox{Ga}_{0.78}\hbox{As}$-Channel MOSFETs With Ultrathin InAlP Native Oxide Gate Dielectric and a Cutoff Frequency of 60 GHz

Enhancement-mode pseudomorphic In
_0.22
Ga
_0.78
As-channel MOSFETs with an ultrathin native InAlP oxide gate dielectric are demonstrated. The gate dielectric, a 3.5-nm-thick oxide grown by wet thermal oxidation from epitaxial InAlP, reduces the gate leakage below that of HFETs based on the same epitaxial structure by more than 10
⁵
times. The devices operate in enhancement mode, with 0.25-μm gate length devices exhibiting a measured threshold voltage of 0.25 V, a peak intrinsic transconductance of 245 mS/mm, and a saturation drain current density of 165 mA/mm. A record-high current gain cutoff frequency
f
_T
of 60 GHz has also been achieved. These results indicate the applicability of InAlP oxide-based InGaAs-channel MOSFETs for use in single power supply RF applications.