LINEAR AND NONLINEAR EXCITONIC ABSORPTION IN SEMICONDUCTING QUANTUM WIRES CRYSTALLIZED IN A DIELECTRIC MATRIX

Spectra of linear and nonlinear absorption of GaAs and CdSe semiconduc ting quantum wires crystallized in a transparent dielectric matrix (in side chrysotile-asbestos nanotubes) have been measured. Their features are interpreted in terms of excitonic transitions and filling of the exciton phase space in the quantum wires. The theoretical model presen ted here has allowed us to calculate the energies of excitonic transit ions that are in qualitative agreement with experimental data. The cal culated exciton binding energies in quantum wires are a factor of seve ral tens higher than in bulk semiconductors. The cause of this increas e in the exciton binding energy is not only the size quantization, but also the ''dielectric enhancement,'' i.e., stronger attraction betwee n electrons and holes owing to the large difference between permittivi ties of the semiconductor and dielectric matrix. (C) 1998 American Ins titute of Physics. [S1063-7761(98)02508-6].