Origin of the Broad Lifetime Distribution of Localized Excitons in InGaN/GaN Quantum Dots

Winkelnkemper, M.; Dworzak, M.; Bartel, T. P.; Strittmatter, A.; Hoffmann, A.; Bimberg, D.

Origin of the Broad Lifetime Distribution of Localized Excitons in InGaN/GaN Quantum Dots

Authors

Description

We derive an energy-dependent decay-time distribution function from the multi-exponential decay of the ensemble photoluminescence (PL) of InGaN/GaN quantum dots (QDs), which agrees well with recently published single-QD time-resolved PL measurements. Using eight-band k.p modelling, we show that the built-in piezo- and pyroelectric fields within the QDs cause a sensitive dependence of the radiative lifetimes on the exact QD geometry and composition. Moreover, the radiative lifetimes also depend heavily on the composition of the direct surrounding of the QDs. A broad lifetime distribution occurs even for moderate variations of the QD structure. Thus, for unscreened fields a multi-exponential decay of the ensemble PL is generally expected in this material system.
5 pages, 4 figures. accepted at Physica Status Solidi