Elastic scattering of phonons and interface polaritons in semiconductor heterostructures

Various mechanisms for the momentum relaxation of phonons and interface polaritons (IP), in semiconductor quantum-well structures, are considered. These are scattering from alloy fluctuations, scattering from charged impurity centers (for LO phonons and IP modes), and scattering from interface roughness (IFR). While all three mechanisms can contribute significantly to the elastic scattering of LO phonons, scattering from IFR is the only important source for momentum relaxation of the IP mode. The size of the IFR is estimated for a few samples reported in the literature by assuming that IFR is responsible for the difference between the experimentally measured and the theoretically calculated electron mobilities. As a result, a minimum interface roughness of between two and five monolayers is obtained. One concludes that if scattering by IFR is the dominant process limiting the low-temperature electron mobility in these samples, then it is a major source for reducing the drift of a nonequilibrium population of phonons and interface polaritons.