Carrier kinetics in a high-optically efficient quantum dot structure

Abstract

We report measurements of the temperature and excitation energy dependence of the photoluminescence (PL) decay time of InAs quantum dots (QDs) embedded in a GaAs quantum well (QW). The investigated structure displays high PL efficiency up to high temperatures (>300 K) due to the effect of the barriers which inhibit carrier escape. It is therefore an ideal structure for device applications, e.g., QD lasers. In the work described here, we have made a detailed study of the recombination dynamics in a QD/QW structure. In particular, we focus on the temperature dependence of the QD PL decay time which in recent years has been a matter of some controversy. In QDs the radiative lifetime is believed to be independent of temperature and so any temperature dependence must be due to other processes, e.g., carrier relaxation and redistribution. We find that, for non-resonant pumping and at low temperatures, the presence of the barriers slows down the PL decay time. However, at high temperatures and/or for resonant pumping of the dots, the barriers have less effect and the PL decay time is governed by carrier redistribution between the dots.