The vertical coupling of InAs quantum dots and their capping with In0. 1Ga0. 9As layers were investigated in order to shift the optical emission of the structures toward longer wavelengths. We observed that both ways can not be used simultaneously by just replacing part of the usual GaAs spacer layer by In0. 1Ga0. 9As because the intermixing of Ga and In atoms is enhanced in stacked layers and causes a blueshift of the emission instead of the expected redshift.
