Optical characteristics of self-assembled InAs/GaAs quantum dots at various temperatures and excitations

Self-assembled InAs quantum dots (QDs) in a GaAs matrix showed excellent optical characteristics, such as strong photoluminescence (PL) and a linear increase of the PL intensity with excitation power. When the QD was highly excited, the excited-state PL at 63 meV above the QD ground-state peak was stronger than the ground-state PL due to increased degeneracy. At 10 K, the measured carrier lifetimes were almost the same throughout the ground-state PL band. This attests to the facts that the PL band is inhomogeneously broadened and that the QD states are well isolated. The decrease in the PL yield with temperature fitted relatively well with thermal activation, with the interesting exception that the yield increased up to 100 K. The time-resolved PL results showed a similar trend with temperature.