Size-dependent radiative decay time of excitons in GaN/AlN self-assembled quantum dots

Abstract

Size-dependent radiative decay time of excitons in GaN/AlN self-assembled quantum dots is reported. Two samples having different average size of quantum dots (QDs) have been investigated at the temperature of 3.5 K. The measurement has revealed that larger-QD sample shows longer photoluminescence (PL) decay time and smaller emission energy than smaller one. The dependence of radiative decay time of the samples on emission energy smoothly connects with each other reflecting the size distribution. The radiative decay time strongly increases by almost three orders magnitude, reaching microseconds, upon increasing the size of QDs. The increase of PL decay time with increasing the size of QDs is attributed to the reduction of oscillator-strength due to the strong built-in electric field in the GaN/AlN heterostructures.