Abstract

Theoretical techniques used to study time dependent electron transport in heterostructures use one or more of the following approximations: i) In Monte Carlo methods the electron is described as a point particle whose transport properties (such as effective mass, scattering rates, etc.) change abruptly when it moves across a boundary. As the electron moves across a boundary, the role of central cell symmetries (i.e., Γ, X, L character) is suppressed; ii) In time dependent quantum description, once again the electron wavepacket is assumed to abruptly see different material properties across a discontinuity. Moreover, the quantum description usually employs a one band effective mass equation that implicitly assumes that the character of the Bloch function is not significantly altered across the regions. The first approach is valid for heterostructures where electrons travel ≈ 1000 Å in each region and where the valley order is not altered across the heterostructure. The second approach is required in heterostructures of dimension ≈ 50 Å where the effects of quantum confinement are important, but where the central cell symmetry is again unchanged across the heterostructure.

© 1991 Optical Society of America