Optical properties of InAs quantum dots embedded in InGaAs/AlGaAs/GaAs structures with different capping layers

The InAs quantum dots (QDs) embedded in Al0.30Ga0.70As/InGaAs/AlGaInAs/Al0.30Ga0.70As structures and covered by strain reduced AlGaInAs capping layer have been investigated in as grown state by means of a photoluminescence method. Three types of QD structures with different QD capping layers: GaAs (#1), Al0.10In0.15Ga0.75As (#2) and Al0.40In0.15Ga0.45As (#3) are compared. It is revealed that the QD emission in the structure with Al0.10In0.15Ga0.75As capping is characterized by the highest PL intensity of the ground state (GS) band and smaller the full with at half maximum (FWHM), compared to #1 and #3 structures. The variation of the GS emission peak versus temperature has been monitored within the range of 10-500K for the as grown film states and compared with shrinkage of the energy bandgaps in the InAs and GaAs bulk crystals. The results show that the efficiency of Ga/Al/In intermixing in #2 and #3 is less than in #1. Finally, the peculiarities of PL spectra of the studied QD structures have been analyzed and discussed.