Investigates the gate length (L/sub g/) dependence of the current-gain cutoff frequency f/sub 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/sub T/ increases with decreasing gate length due to reduced capacitance as dictated by the charge control model. An effective saturation velocity of 1.3*10/sup 7/ cm/s is deduced from the f/sub T/-L/sub g/ dependence. A maximum f/sub T/ of 112 GHz is measured on an L/sub g/=0.15 mu m device, limited mainly by parasitic charge in the AlInAs.<<ETX>>