Study of self-assembled InAs quantum dot structure covered by InxGa1-xAs(0<= x <= 0.3) capping layer

InAs self-assembled quantum dots(QDs) covered by 3-nm-thick InxGa1-xAs(0 le ss than or equal tox less than or equal to0.3) capping layer have been grow n on GaAs(100) substrate. Transmission electron microscopy shows that InGaA s layer reduces the strain in the InAs islands,and atomic force microscopy evidences the deposition of InGaAs on the top of InAs islands when x = 0.3. The significant redshift of the photoluminescence (PL) peak energy and the reduction of PL linewidth of InAs quantum dots covered by InGaAs are observ ed. In addition,InGaAs overgrowth layer suppresses the temperature sensitiv ity of PL peak energy. Based on our analysis, the strain-reduction and the size distribution of the InAs QDs are the main cause of the redshift and te mperature insensitivity of the PL respectively.