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 7nm, 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. (c) 2004 Elsevier B.V. All rights reserved.