AN ANALYTIC APPROACH TO THE REAL-SPACE TRANSFER IN SEMICONDUCTOR SUPERLATTICES WITH HIGHLY DOPED BARRIERS

The parallel transport in semiconductor superlattices and the associat ed transfer of electrons from high-to low-mobility layers are treated on the basis of quantum kinetic equations. Due to the assumed dominant role of impurity scattering in the barriers, the description of trans port properties simplifies considerably. The superlattice band structu re is replaced by a two-band model that simulates electronic states in the narrow quantum wells and in the adjacent broad barriers. Using th e quasi-elastic approximation for the electron-phonon scattering in th e narrow miniband, analytical results are derived for the current dens ity that provide a qualitative understanding of the main physics takin g place in the device. The approximate description of the real-space t ransfer encompasses scattering on acoustic and optical phonons as well as on impurities. Particular emphasis is pur on the negative differen tial resistance and its dependence on the well width.