Morphology and optical properties of self-assembled In0.5Ga0.5As quantum dots with different spacer layer thickness

Uncapped double stacked Ino.5Gao.5As quantum dots (ODs) with different spacer layer thicknesses were grown using metal-organic chemical vapour deposition (MOCVD). The precursors used for the growth of the GaAs layer and Ino.5Gao.5As ODs were trimethylgallium (TMGa), trimethylindium (TMln), and arsine (AsH3). The morphology and optical properties of the self-assembled Ino.5Gao.5As ODs were investigated and characterized using atomic force microscopy (AFM) and photoluminescence (PL). The AFM images revealed that the sizes of the dots on the topmost were not uniformly distributed. The average size of the dots fluctuated as the GaAs spacer layer thickness increased. A room temperature PL measurement was used to establish the quality and quantity of the stacked ODs. The PL peak position remained at 1148 nm for all samples of ODs; however, the PL intensity increased as spacer layer thickness increased. The structure of the spacer layer in the stacked 00 affected the morphology of the topmost surface of the ODs. The PL measurement coherently reflected the AFM characterization, in which the strong PL spectra were caused by the uniformity and high density of the ODs. The surface morphology, structure, and optical properties of the stacked ODs are attributed to seed-layer (first layer) formation of dots and spacer layer structures.