The ground-state energy of excitons confined in microspherical crystallites with a finite-height potential wall is studied variationally as a function of the particle radius in the so-called strong-confinement regime. Exciton energies for dot radii in the range 5-40 Å are calculated and compared with experimental and theoretical data for CdS, CdSe, PbS and CdTe crystallites. This comparison shows that the effective-mass approximation and spherical confinement geometries are appropriate for all of the particle sizes. Our results also show that the quantum dot cannot be modelled using an infinite-barrier-height potential in the strong-confinement regime.

Electron states in a magnetic quantum ring are investigated. The electron is assumed to be confined to a plane in the presence of a magnetic field which is zero within the ring a

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Optical properties of asymmetrical multiple quantum wells for the construction of quantum cascade lasers are calculated, and expressions for the electronic states of asymmetrical multiple quantum wells are presented. The gain and differential cross-section for an electron Raman scattering process are obtained. Also, the emission spectra for several scattering configurations are discussed, and the corresponding selection rules for the processes involved are studied; an interpretation of the singularities found in the spectra is given. The electron Raman scattering studied here can be used to provide direct information about the efficiency of the lasers.

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