Quantum corrected Monte Carlo simulation for semiconductor devices
An effective conduction-band edge (ECBE) equation has been derived based on the Schrödinger-Bohm model by eliminating the density-gradient term. When applied to the Monte Carlo (MC) simulation of semiconductor devices using the quantum corrected Boltzmann transport equation (BTE), this method has the advantage of not being affected by density fluctuations.
The existing Bohm-based and Wigner-based quantum correction models are unified under a single (ECBE) method via a density-dependent quantum correction coefficient. The difference between our ECBE model and the effective potential model is also described in detail. The utility and accuracy of the ECBE method is tested on a simple problem of charge confinement in an infinite potential well and of particle tunneling through a step potential barrier. Both results indicate that the ECBE method is a viable approach to the quantum correction of the BTE.
The ECBE model has been applied to the MC simulations of double gate MOSFETS. Unlike the simulation by the hydrodynamic model, the MC method does not need to assume a mobility model which is difficult to establish for nanoscale devices. The quantum effects affecting both the potential and charge density in the device are successfully simulated. Our study shows that the coupling between the two channels in asymmetric double gate devices is affected more strongly by the silicon-layer thickness than by the channel length. Also, the drain induced barrier lowering effect becomes important for the double gate MOSFETs once the channel length becomes shorter than 20nm.