Quaternary Barrier InAlGaN HEMTs With $f_{T}/f_{max}$ of 230/300 GHz

摘要

Depletion-mode quaternary barrier $hbox{In}_{0.13}hbox{Al}_{0.83}break hbox{Ga}_{0.04}hbox{N}$ high-electron-mobility transistors (HEMTs) with regrown ohmic contacts and T-gates on a SiC substrate have been fabricated. Devices with 40-nm-long footprints show a maximum output current density of 1.8 A/mm, an extrinsic dc transconductance of 770 mS/mm, and cutoff frequencies $f_{T}/f_{max}$ of 230/300 GHz at the same bias, which give a record-high value of $surd f_{T} cdot f_{max} = hbox{263} hbox{GHz}$ among all reported InAl(Ga)N barrier HEMTs. The device speed shows good scalability with gate length despite the onset of short-channel effects due to the lack of a back barrier. An effective electron velocity of $hbox{1.36} times hbox{10}^{7} hbox{cm/s}$, which is comparable with that in the state-of-the-art deeply scaled AlN/GaN HEMTs, has been extracted from the gate-length dependence of $f_{T}$ for gate lengths from 100 to 40 nm.