Dielectrically enhanced excitons in semiconductor-insulator quantum wires:Theory and experiment

We present both theoretical and experimental investigations of optical prop erties of excitons in semiconducror-insulator quantum wires. Spectra of lin ear and nonlinear absorption, photoluminescence and its polarization, photo luminescence excitation, time-resolved photoluminescence of GaAs, CdSe, and InP quantum wires 4-6 nm in diameter, crystallized in dielectric matrix, d emonstrate the prominent excitonic behavior. In these structures an essenti al difference of dielectric constants of constituent materials lends to a c onsiderable enhancement of excitons, the binding energies ranging from 120 meV to 260 meV and exciton transitions being well distinguished in nanowire s with sufficient dispersion of diameter even at room temperature. A theore tical approach to calculations of the exciton parameters in a semiconductor - insulator cylindrical quantum wire of finite diameter is developed. This approach accounts for a band-gap renormalization due to the spatial confine ment and self-image effect, as well as for a dielectric enhancement of the electron-hole interaction. The calculated exciton transition energies and a bsorption spectra are consistent with the experimental results.