  The Wave Function Matching (WFM) technique has recently been developed for
the calculation of electronic transport in quantum two-probe systems. In terms
of efficiency it is comparable with the widely used Green's function approach.
The WFM formalism presented so far requires the evaluation of all the
propagating and evanescent bulk modes of the left and right electrodes in order
to obtain the correct coupling between device and electrode regions. In this
paper we will describe a modified WFM approach that allows for the exclusion of
the vast majority of the evanescent modes in all parts of the calculation. This
approach makes it feasible to apply iterative techniques to efficiently
determine the few required bulk modes, which allows for a significant reduction
of the computational expense of the WFM method. We illustrate the efficiency of
the method on a carbon nanotube field-effect-transistor (FET) device displaying
band-to-band tunneling and modeled within the semi-empirical Extended H\"uckel
theory (EHT) framework.

Materials Science