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

GaAs/Al_0.30Ga_0.70As/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: (Al_0.30Ga_0.70As (#1) and Al_0.10Ga_0.75In_0.15As (#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 Al_0.10Ga_0.75In_0.15As capping layer. The blue shift of PL spectra is detected after annealing and this shift is more significant in the structure with Al_0.10Ga_0.75In_0.15As 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.