Materials with a light effective mass and high mobility are known to provide better performance for long channel transistors. However, with transistor dimensions scaling to sub-10 nm lengths, source to drain tunneling (SDT) becomes a major performance limiting factor for high mobility materials. In this paper, we examine the effect of SDT on the performance of germanium-tin (GeSn) short channel Nanowire (NW) p-MOSEFTs using rigorous ballistic quantum transport simulations. We simulate GeSn NWs in different transport orientations and with Sn mole fraction values of 0.05 and 0.11 to identify the channel direction with optimum effective mass to limit SDT. We also examine the role of reduced source/drain doping in enhancing the on-state performance of GeSn NWs by limiting SDT current in off-state. © 2018 IEEE.