Low-Field Mobility and Quantum Effects in Asymmetric Silicon-Based Field-Effect Devices

Abstract

Though asymmetric MOSFET structures are being designed in response to small-geometry effects, the performance estimates of such devices often rely on the conventional device description, and neglect to properly account for the interplay between quantum effects and the effects of asymmetry. In this paper, we investigate the low-field transport in a highly asymmetric MOSFET structure, characterized by a p+-implant at the source end, by using a Monte Carlo—Poisson simulation with the quantum effects incorporated through an effective potential. We observe that highly-pronounced asymmetry leads to ballistic transport features, which become suppressed by the inclusion of quantum effects. We prove that mobility degradation is an essentially non-equilibrium signature of quantum mechanics, independent of the well-established equilibrium signatures (charge set-back and gap widening). Consequently, in order to properly estimate the device performance, it becomes important to account for the channel mobility degradation due to quantum effects.