ARE THERE TAMM-STATE DONORS AT THE INAS-AISB QUANTUM-WELL INTERFACE

An explanation of the temperature dependence of the electron concentration in InAs/AlSb quantum wells, along with the high electron mobilities found, calls for a model involving a high concentration of interface donors whose electron scattering cross section is much less than that of conventional point defect donors. We postulate that the interface donors are in fact not point defects, but a Tamm-state-like band of de-localized interface states not associated with defects, but with the strong discontinuity in the periodic potentials on the two sides of the interface. Heuristic arguments supporting this hypothesis are given.