The development of spin MOSFETs has been stymied by low values of magnetoresistance (MR) measured in
experiments. Simulation studies have largely focused on diffusion driven or ballistic transport in the semiconductor
and a simplistic treatment of spin injecting contacts. Here we demonstrate a novel framework to simulate
spin injection and spin transport in semiconductors in the drift-diffusion regime and a tunneling based model
for spin injecting contacts thereby enabling simulation and optimization of experimental devices.