Abstract
The optical properties of InAs quantum dots (QDs) embedded in a GaAsSb matrix with different delta (δ)-doping levels of 0, 2, 4, and 6 electrons per dot (e−/dot), incorporated to control the occupation of QD electronic states, are studied by photoluminescence (PL) spectroscopy. The time-resolved PL data taken at 10 K reveal that the increase of δ-doping density from 2 to 6 e−/dot decreases the recombination lifetime of carriers at ground states of the QDs from 996 ± 36 to 792 ± 19 ps, respectively. Furthermore, the carrier lifetime of the sample with 4 e−/dot is found to increase at a slower rate than that of the undoped sample as temperature increases above 70 K. An Arrhenius plot of the temperature dependent PL intensity indicates that the thermal activation energy of electrons in the QDs, required for carrier escape from the dot ground state to continuum state, is increased when the δ-doping density is high enough (>4 e−/dot). These results are attributed to the enhanced Coulomb interaction of electrons provided by the δ-doping, leading to reduced thermal quenching of the PL.
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