Evolution of current transport models for engineering applications

The continuous minimum feature size reduction of microelectronic devices, institutionalized by the ITRS roadmap, has been partly enabled by the support of TCAD tools. Device modeling tools have been established on base of the ground-breaking work of Scharietter and Gummel (1969). Since then, numerous transport models of increasing complexity have been proposed. Modern microelectronic devices are characterized by the transition between large reservoirs with strong carrier scattering, and small regions where quantum effects dominate. This explains the general interest to incorporate both classical and quantum-mechanical modeling approaches into macroscopic device simulators. To first order, quantum correction models can account for these effects. A more rigorous approach is to derive macroscopic transport models from the Wigner equation, which leads to the density-gradient model (Wettstein et al., 2001), or to self-consistently couple Schrodinger-Poisson solvers with the transport model used (Heinz et al., 2002). Even more rigorously, the Wigner equation can directly be solved by means of the Wigner Monte Carlo method (Kosina et al., 2002). An overview and examples of these approaches, namely higher-order transport models, the different quantum correction approaches, and the Wigner Monte Carlo method are presented.