Emission and HR-XRD varying in GaAs/AlGaInAs heterostructures with InAs quantum dots at annealing

GaAs/Al0.30Ga0.70As/AlGaInAs/ heterostructures grown by molecular beam epitaxy with embedded InAs quantum dots (QDs) have been investigated before and after thermal annealing at 640 °C for 2 h. Two types of QD structures with the different compositions of capping layers: (Al0.30Ga0.70As (#1) and Al0.10Ga0.75In0.15As (#2)), are studied using the photoluminescence (PL), X-ray diffraction (XRD) and high-resolution XRD (HR-XRD) techniques. The high PL intensity, smaller half width of PL bands and lower energy of the ground state (GS) emission are detected in the structure with the Al0.10Ga0.75In0.15As capping layer. The blue shift of PL spectra is detected after annealing and this shift is more significant in the structure with Al0.10Ga0.75In0.15As capping as well. The last effect has been explained by the efficient Ga/In inter-diffusion at the AlGaInAs/InAs QD interface in #2 owing to the smaller In-As binding energy in comparison with Al-As and Ga-As ones in the studied alloy. The composition variation of the QDs and quantum wells (QWs) due to Ga/In intermixing at annealing has been modeled on the base of the numerical simulation of HR-XRD scans with the help of X′ Pert Epitaxy software.