Excitonic transitions in (GaAs)1-x(Ge2)x/GaAs multilayers grown by magnetron sputtering

We report on excitonic transitions observed at room temperature in multilayers of (GaAs)1-x(Ge2)x/GaAs grown by magnetron sputtering. We attribute the observation of the exciton absorption at room temperature to confinement effects on the bound electron-hole pairs inside the Ge-rich layers of the (GaAs)1-x(Ge2)x alloys. From secondary ions mass spectroscopy these layers are measured to be 50, 33, and 30 nm in full width at half maximum (FWHM), for three different samples. These layers alternate with (GaAs)1-x(Ge2)x alloy layers of very low Ge concentration that can be considered of plain GaAs, ∼360nm in thickness for two samples and 240 nm for a third one. The observed transition energies of the exciton are very close to ≈1eV both at 300 and 4 K. A calculation of exciton energy-level spacing and transition probabilities provides acceptable values for the exciton transition energies observed, considering a triangular quantum well as an approximation to the Ge profile in the confinement layers. The observed excitonic FWHM remain nearly constant at all temperatures examined (300-4 K). © 1998 American Institute of Physics.

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