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 op tical characteristics, such as strong photoluminescence (PL) and a linear i ncrease of the PL intensity with excitation power. When the QD was highly e xcited, the excited-state PL at 63 meV above the QD ground-state peak was s tronger 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 bro adened and that the QD states are well isolated. The decrease in the PL yie ld with temperature fitted relatively well with thermal activation, with th e interesting exception that the yield increased up to 100 K. The time-reso lved PL results showed a similar trend with temperature.