The influence of quasi-localized carrier states on the optical properties of size-quantizing structures

Abstract

We considered the optical properties of size-quantizing semiconductor structures with quasi-localized electron states. In particular, the formulae we obtained allow us to determine the optical absorption due to electron transitions from the localized ground state to an excited quasi-localized (resonant) one. The calculations were carried out for objects of various dimensionalities, that is for a layered structure (quantum well) and a spherically symmetric irregularity (quantum dot), suggesting a certain model potential. The obtained results qualitatively correspond to the experimental observations, yielding an intermediate picture, when compared to the electronic transitions to an excited bound state and to a delocalized band state. Having derived a formula for the absorption cross-section of a single quantum well, we also obtained expressions for the corresponding corrections to the absorption coefficient, refractive index and dielectric constant of the multi-quantum well structure as functions of the frequency of incident light and the parameters of the quantum wells and barriers. The results may be useful in designing quantum well infrared photodetectors.