MULTIPLE EXCITONIC FEATURES IN LOW-CARBON CONTENT AL-CHI-GA1-CHI-AS

Photoluminescence (PL) results are reported on AlxGa1-xAs containing very low carbon concentrations grown by metalorganic vapour-phase epitaxy. Multiple excitonic transitions are observed which cannot be attributed to variations in aluminum fractions. The localization energies of these multiple excitonic features, which are only observed in layers with aluminum fractions greater than 0.2, varies from 2 to 8 meV. This indicates that some of these transitions must be due to excitons bound to non-shallow centres, although their precise origin is still unknown.