Shape and Interband Transition Behavior of InAs Quantum Dots Dependent on Number of Stacking Cycles

Abstract

InAs/GaAs multistacked quantum dot (QD) layers were grown by using molecular beam epitaxy with various numbers of stacking cycles to investigate the shape and the interband transition in the InAs QDs. The appearance of another photoluminescence (PL) peak on InAs/GaAs QDs with more than six stacking cycles originated from the change of the QDs from an isotropic pyramidal shape to an elongated anisotropic pyramidal shape. Dislocation lines along the [110] direction existing on the InAs/GaAs QDs with more than six stacking cycles were attributed to the existence of excessive strain fields. Scanning transmission electron microscope and atomic force microscope images showed that the QD shape in the [110] direction was elongated without any remarkable change in the volume of the QDs. These results indicate that the shape of the InAs/GaAs QDs was strongly affected by the number of the stacking cycles and that the appearance of another PL peak is related to the change of the QD shape.