Electron Transmission Across Epitaxial Interfaces

Ballistic transmission of electrons is possible in principle across the atomically abrupt epitaxial interfaces that can be formed between silicon and several metallic silicides. We will discuss the transmission probability at these interfaces. Kinematic constraints play a large role; it is necessary that the transmitted state have the same energy, parallel momentum, and rotational symmetry (with respect to the interface) as the incident state. The simplest calculation of the transmission coefficient including these constraints is an effective mass approximation. This simple approximation, however, omits the detailed spatial dependence of the wavefunctions which is important in the matching process. Wavefunctions that have very different spatial character in the material on either side of the interface do not couple strongly with each other even if the kinematic constraints are satisfied. We have studied these spatial dependencies using wavefunctions calculated by the LAPW method, which gives band structures in good agreement with experiment for these materials. We will discuss a surface Green function matching technique based on these wavefunctions which directly gives the transmission coefficient.