Bandstructure and ballistic transport in semiconductor-heterostructures

Using an envelope-function-formalism and the effective-mass-approximation including nonparabolicity, the bandstructure of semiconductor heterostructures is calculated under applied electric field. The resonant behavior of open quantum systems such as a five-period-superlattice between highly doped contacts is found by calculating the position of the poles of the transmission function in complex energy. Semiconductor structures discussed are single barrier, double barrier, five- and ten-period-superlattices. The current through the structures is calculated assuming ballistic electron transport. In the transport calculation, special attention is paid to three terminal devices. The calculated results for the transfer ratio, i.e. ratio of injected current to transmitted current, are in good quantitative agreement with recent experiments. To describe the temperature dependence of the current, a model for calculating the Fermi-level in the contacts and inside the structure is developed which accounts for the broadening and the shift of the donor levels observed in the high doping regime. (author)