Recent advances in the spherical harmonics expansion (SHE) method of the Boltzmann transport equation (BTE) allow for the accurate solution of the BTE on arbitrary three-dimensional device geometries [57], full-band effects [48, 58, 59], rare scattering events (e.g. impact ionization) [60], carrier-carrier scattering [61], charge carrier recombination/generation [62], small signal analysis [63, 47], quantum mechanics [64, 49], and hot carrier degradation [46]. The SHE method has been developed to a point where it is now an attractive alternative to the common Monte Carlo (MC) method, which has a square root dependence of its accuracy on CPU time [44]. As discussed in Section 2.4, the Monte Carlo method suffers from inherent stochastic noise in the solution and the requirement of sufficiently small time steps to achieve self-consistency with Poisson’s equation. An expansion of the BTE using spherical harmonics does not impose such restrictions, since it is a deterministic approach. In the course of this work the SHE simulator ViennaSHE [65] has been extended and used to solve BTE (cf. Equation (2.27)).