Exciton recombination dynamics in InxGa1-xAs/GaAs quantum wells.

Abstract

Low-temperature decay times ${\mathrm{\ensuremath{\tau}}}_{\mathrm{PL}}$ are reported for a series of ${\mathrm{In}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As/GaAs quantum wells. These show a nearly linear increase with increasing thickness (4\ensuremath{\le}${\mathit{L}}_{\mathit{z}}$\ensuremath{\le}10 nm, x=0.15) but recombination in the widest well (12 nm) is dominated by nonradiative effects. The decay time increases almost linearly with temperature up to 50 K, as expected for free excitons. An increase in ${\mathrm{\ensuremath{\tau}}}_{\mathrm{PL}}$ with increasing In composition (0.05\ensuremath{\le}x\ensuremath{\le}0.25, ${\mathit{L}}_{\mathit{z}}$=8 nm) is also observed. Wells with different In compositions exhibit a similar temperature behavior and there is a weak influence of strain on the decay time. Additional peaks in the photoluminescence spectra occur to the low-energy side of the free-exciton peaks. These features, which exhibit longer decay times, are attributed to excitons localized in In-rich islands arising from indium segregation.