Origin of the broad lifetime distribution of localized excitons in InGaN/GaN quantum dots

Abstract

AbstractWe derive an energy‐dependent decay‐time distribution function from the multi‐exponential decay of the ensemble photoluminescence (PL) of Inx Ga1–x N/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. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)