Tight binding simulation of quantum transport in interband tunneling devices

We have studied quantum transport in both Si and GaAs based interband tunneling diodes (ITD´s). In the simulation, a non-equilibrium Green´s function method based on an empirical tight binding theory has been used to take into account evanescent-wave matching at interfaces and realistic band structures. Comparison has been made between the results of our multiband (MB) model and those of conventional two-band (2B) model which assumes the band extrema exist at the /spl Gamma/ valley. As a result, it is found that the current-voltage (I-V) characteristics of the Si ITD have considerably smaller peak current density than the conventional 2B model, since our MB model reflects correctly the indirect gap band structure. On the other hand, in the GaAs ITD, there is small difference between the two models, because tunneling occurs between the conduction band minimum and the valence band maximum (i.e. /spl Gamma/ point). It is also found that the matching of evanescent electron modes is essentially necessary to include the valley-mixing effects at the tunneling interfaces.