Electron–interface-phonon interaction and scattering in asymmetric semiconductor quantum-well structures

Abstract

The interaction Fr\ohlich-like Hamiltonian between an electron and interface optical phonons in asymmetric single and step quantum-well (QW) structures is obtained and studied. We observe that the behaviors of electron--interface-phonon coupling functions as functions of wave number k have two anomalies. The first is that, in an asymmetric single QW and general step QW, the interaction between an electron and the lowest frequency interface mode is large in the vicinity of the Brillouin-zone center. The second anomaly is that in step QW's the interaction between an electron and the fifth interface mode has a maximum which relates to the inflection point in the dispersion (${\mathrm{\ensuremath{\omega}}}_{5\mathrm{\ensuremath{-}}}$k) plot. The physical origins of these two anomalies have been analyzed. The electron--interface-phonon-scattering rates for intrasubband and intersubband transitions in asymmetric single and step QW structures are also calculated and are given as functions of well width, step width, and step height. It is shown that the electron scattering depends strongly on the potential parameters, and the usual selection rules for these transitions break down in asymmetric heterostructures.