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

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