Simulation of Electron Transport in High-Mobility MOSFETs: Density of States Bottleneck and Source Starvation

20 nm InGaAs-based MOSFETs are studied using dc and transient Monte Carlo simulations and self-consistent Schrodinger-Poisson solutions accounting for nonparabolic corrections. The latter simulations show that nonparabolicity can boost the carrier concentration in the InGaAs channel by up to 35% with respect to calculations based on parabolic models, while Monte Carlo simulations show that an optimization of the source, channel, and source/channel regions can significantly improve the performance of the devices. This optimization overcomes a problem that results from the low density- of-states (DOS) in materials with low effective mass, which appears in the quasi-ballistic limit: The inability of the source region to sustain a large flow of carriers in 'longitudinal' velocity states in the channel ('source starvation'), unless the momentum relaxation rate and/or the doping density in the source are sufficiently large.