Recent studies on light-trapping in solar cells have been primarily based on either optical simulations, or fabrication of light-trapping various structures (nanowires, nanoholes, nanocones, etc) and absorption measurements. However, design of an efficient solar cell must consider both the electromagnetic wave propagation and carrier transport properties simultaneously. In GUNAM, we perform combined electromagnetic and carrier transport simulations of solar cells to gain insights on the optimum light trapping structures, and doping and contact schemes. Various loss mechanisms (surface, bulk and Auger recombinations), mobility decrease and band gap shrinking with doping are being implemented in our models. We are working on extending our model to heterojunction solar cells.