Exciton resonance reflectivity study of quantum well wires

We report on the first observation of the exciton resonant reflection from a directly grown array of isolated quantum-well-wires. Structures contaned 30 GaAs/AlAs double layers were grown on (311) GaAs substrate by conventional elemental source MBE. GaAs wire-like clasters with an orientation along [233] and size of 32/10.2 Å were introduced inside one of the central AlAs layers. The expected distance between nearest clusters is about 160 Å. In spite of much smaller effective volume occupied by excitons in these clusters, as compared to that in a single quantum well, the quantum-well-wire structures demonstrate much lager resonance amplitude of the reflection spectra. We extracted excitonic parameters from these spectra and found that the exciton oscillator strength in the quantum-well-wires is more than 10 time higer than that in the enviroment superlattice. A 30% anisotropy of the exciton oscillator strength in the quantum-well-wire have been observed. The theory of non-local dielectric responce is extended to calculate reflection spectra from the structures with a grating of quantum-well-wires. A functional relationship between the reflection coefficient and the envelope wave function of an exciton in the structure has been established