EFFECTS OF A MONOLAYER ON THE ELECTRON-PHONON SCATTERING RATES IN A QUANTUM-WELL - DIELECTRIC CONTINUUM VERSUS HYBRID MODEL

Recent publications have suggested that a reduction in the total elect ron-phonon scattering rate in a quantum well can be achieved by the in clusion of a monolayer of a different material. The predictions have b een based upon two distinct models: the dielectric continuum (DC) mode l and the hybrid model. In the DC model the symmetric phonon modes are modified upon introducing the monolayer (via the electromagnetic boun dary conditions) and hence a reduction in the intrasubband electron-ph onon scattering rate is expected. In the hybrid model it is the antisy mmetric modes that are modified and a reduction in the intersubband sc attering rate is thus expected. It is shown here, however, that when t he calculations are done correctly the calculated rates are approximat ely the same for both models if the thickness of the monolayer is vani shingly small and the electron wave functions are assumed to be unchan ged. This implies that the inclusion of a monolayer of a finite thickn ess in a quantum well will only have a marginal effect on the total sc attering rates, even though the mode spectra are changed. Our results also serve as an additional test of the hybrid model when applied to a more complicated system than a single quantum well. Again, an agreeme nt is found between the two models when calculating the total electron -phonon scattering rates. We emphasize, however, that unlike the DC mo del the hybrid model can also correctly model Raman spectra. (C) 1998 American Institute of Physics. [S0021-8979(98)00103-0].