Matrix compression for spherical harmonics expansions of the Boltzmann transport equation for semiconductors

We investigate numerical solution schemes for the semiconductor Boltzmann transport equation using an expansion of the distribution function in spherical harmonics. A complexity analysis shows that traditional implementations using higher-order expansions suffer from huge memory requirements, especially for two- and three-dimensional devices. To overcome these complexity limitations, a compressed matrix storage scheme using Kronecker products is proposed, which reduces the asymptotic memory requirements for the storage of the system matrix significantly. The total memory requirements are then dominated by the memory required for the unknowns. Numerical results demonstrate the applicability of our method and confirm our theoretical results.