Effect of InxGa1−xAs strain release layers on the microstructural and interband transition properties of InAs/GaAs quantum dots

The effect of InxGa1−xAs (x=0.1, 0.2) asymmetric strain release layers (ASRLs) on the microstructural and the interband transition properties of InAs/GaAs quantum dots (QDs) grown by using molecular beam epitaxy (MBE) and atomic layer epitaxy was investigated by using high-resolution transmission electron microscopy (HRTEM) and photoluminescence (PL) measurements. When the thickness of the ASRL covering the QDs was increased in the range between 0 and 5 nm, the PL peak corresponding to the interband transitions shifted to longer wavelengths due to strain relaxation. However, when the thickness of the ASRL was increased above approximately 7 nm, the peak shifted to shorter wavelengths due to the local interdiffusion of In and Ga atoms between the InxGa1−xAs capping layer and the InAs QDs as a result of the localized strains in the InxGa1−xAs capping layer and the InAs QDs. These results provide important information on the tunable feasibility of the interband transitions in the InAs/GaAs QDs utilizing the InxGa1−xAs capping layer.