Phase separation growth of InGaAs cap layer on InAs/GaAs quantum dots

The mechanisms responsible for the shift of the photoluminescence spectrum to longer wavelength by depositing an InGaAs cap layer on InAs/GaAs quantum dots are studied in detail. It is demonstrated that the phase separation growth of InAs and GaAs rather than the stress in the InAs quantum dots is the main reason for the wavelength shifts. AFM images of a single InAs quantum dot are presented and the reason for the differences between AFM and SEM images is discussed.