Investigation of Source Starvation in High-Transconductance III–V Quantum-Well MOSFETs

In this article, a detailed simulation study of high-performance InGaAs quantum-well (QW) MOSFETs is presented. We demonstrate that the limited free carrier density in the access region leads to a significant source starvation effect in the saturation regime, which limits the maximum transconductance ( ${g}_{m}$ ). By coupling ballistic 2-D quantum mechanical simulations with an original semiclassical model for source starvation, we are able to reproduce quantitatively the ${V}_{\text {GS}}$ – ${g}_{m}$ characteristics of three successive device generations differing only in the design of their access region. Source starvation is approximated as a quasi-equilibrium phenomenon characterized by a nonlinear, current-dependent voltage drop in the access region that reduces injection into the channel at high currents. Even in the most recent record device with a ${g}_{m}$ peak of 3.45 mS/ $\mu \text{m}$ , source starvation is found to have a negative impact. An extrapolation of our model furthermore suggests that source starvation will become a major performance bottleneck in future device realizations with lower trap densities.