Dependence of current-gain cutoff frequency on gate length in submicron GaInAs/AlInAs MODFETs

Abstract

We have investigated the gate length (Lg) dependence of the current-gain cutoff frequency fT in lattice-matched GaInAs/ AlInAs MODFETs. The transconductance is found to be relatively insensitive to gate length in this submicron regime, while the fT increases with decreasing gate length due to reduced capacitance as dictated by the charge control model. An effective saturation velocity of 1.3 × 107cm/s is deduced from the fT−Lg dependence. A maximum fT of 112 GHz is measured on an Lg = 0.15 μm device, limited mainly by parasitic charge in the AlInAs.