RF Performance of Si/SiGe MODFETs: A Simulation Study

Abstract

The microwave performance potential of Si/SiGe pseudomorphic MODFETs are studied, in comparison to state of the art InGaAs pseudomorphic HEMTs. Both devices have equivalent structures corresponding to a physical HEMT used for calibration. We use an RF analysis technique based on transient Monte Carlo simulations to estimate the intrinsic noise figures, the RF figures of merit f_T and f_max, and the effect of contact and gate resistances. Both devices exhibit velocity overshoot below the gate region. It is shown that the difference in noise figures and f_T values can be mainly attributed to differences in device channel velocity, f_max exhibits a strong dependence on device contact resistance, eroding some of the performance advantage of the pseudomorphic HEMT.