Effective mass versus tight-binding: Where is the discord?

We address the use of the tight-binding and effective mass approximations (TB and EMA) for the calculation of transport properties in silicon nanowires (SiNWs). Three different transport scenarios are considered within a non-equilibrium Green's function approach: ballistic transport, tunneling under a potential barrier, and transport through a potential well. In the first two cases TB and EMA provide roughly similar conductances. For the potential-well case, however, the EMA approach fails to reproduce fano resonances. These discrepancies are strongly reduced at room temperature.