Effect of spacer layer thickness on morphology and optical properties of self-assembled in0.5ga0.5as quantum dots

Abstract

The effect of GaAs spacer layer thickness on morphology and optical properties of Ino.sGao.sAsIGaAs quantum dots (QDs) has been studied. The uncapped double stacked 1no.sGaosAs QDs were grown using metal-organic chemical vapour deposition (MOCVD with trimethylgallium (TMGa), trimethylindium (TMln) and arsine (AsH3) precursors. All samples have been investigated and characterized using atomic force microscopy (AFM) and photoluminescence (PL). The AFM images revealed that. the size of the dots on the top most layer is not uniformly distributed. Several large dots formed on the top-most layer with different spacer layer thickness. The average size of the dots fluctuated with the increase of GaAs spacer layer thickness. Room-temperature PL measurement was used to establish the quality and quantity of stacked QDs structures. The PL peak position was remained at 1148 nm for all samples of QDs, however the PL intensity has increased with the increase of the spacer layer thickness. Structure of spacer layer in the stacked QD structures has affected the top-most surface morphology of the QDs. The PL measurement have coherently reflected the AFM characterization. in which the strong PL spectra is caused by the uniformity and high density of the QDs. Surface morphology. structure and optical properties of stacked QDs structures are also attributed to the seed (under-layer) dots formation and spacer layer structures.