Photoluminescence variation in In As quantum dots embedded in InGaAs/AlGaAs quantum wells at thermal annealing

Photoluminescence (PL) and its temperature dependence have been studied in MBE grown InAs quantum dots (QDs) embedded in GaAs/Al0.3Ga0.3As/In0.15Ga0.85As/AlxGa1-xAs/GaAs quantum wells (QWs) in dependence on the composition of capping AlxGa1-xAs layers and after the thermal annealing. Two types of capping layers (GaAs and Al0.3Ga0.7As) were investigated and the PL parameters of such structures have been compared. The annealing has been done for some part of the QD structures at 640 degrees C for 2 h. It is shown that thermal annealing initiates the shift of PL peak positions into the high energy spectral range and the value of this shift depends on the composition of capping layers. Temperature dependences of PL peak positions in QDs have been analyzed in the range of 10-300 K and compared with the temperature shrinkage of the band gap in the bulk InAs crystal. This permits to investigate the efficiency of the Ga(Al)/In inter diffusion processes in dependence on the capping layer compositions and thermal annealing. Experimental and fitting parameters obtained for InAs QDs have been compared with known ones for the bulk InAs crystal. It is revealed that the efficiency of the Ga(Al)/In inter diffusion depends essentially on the capping layer compositions. The thermal quenching of integrated PL intensities has been studied in both types of QD structures as well. The fast thermal decay of the integrated PL intensity in the structure with the GaAs capping layer in comparison with the other one with AlGaAs capping is revealed. Finally the reasons for higher thermal stability of the structure with AlGaAs capping layer have been analyzed and discussed. (C) 2013 Elsevier B.V. All rights reserved.