Optical properties of InAs/AlyGa1−yAs/GaAs quantum dot structures

We present a detailed study, by means of photoluminescence measurements, of the optical properties of self-assembled InAs/AlyGa1−yAs/GaAs quantum dot (QD) structures, grown by Atomic Layer Molecular Beam Epitaxy. We found a blue shift of the fundamental QD energy transition when increasing the Al content in the barrier. The comparison of the experimental data with previous findings and with a simple effective mass model suggests that the emission blue shift cannot be completely attributed to the increase of the confining barriers band gap. At the same time we show that the use of ALMBE allows a better control of the QD size distribution with respect to standard MBE growth. The increase of the barrier height enhances the QD radiative efficiency at high temperature, allowing to observe the QD emission up to T=430 K. Important pieces of information on the thermal activation of non radiative channels are obtained by comparing the QD PL temperature dependence with non-resonant and resonant excitation of the QD levels.