Growth and vertical correlation of CdSe/ZnSe quantum dots

The growth and vertical organization of CdSe quantum dots in three-layer st acks consisting of CdSe with a nominal thickness of 2.5 monolayers (ML) and ZnSe spacers with thicknesses between 10 and 20 ML was investigated by ref lection high energy electron diffraction during the growth and different tr ansmission electron microscopy techniques. The samples were grown by molecu lar beam epitaxy at 400 degreesC. It was found that up to 10 ML spacer thic kness all three CdSe layers and ZnSe spacers form one broad (Cd, Zn)Se allo y layer with a small Cd concentration containing Cd-rich islands with a siz e of similar to 15 nm. For spacers with a larger thickness (12-20 ML) three separated ternary (Cd, Zn)Se layers are observed which contain Cd-rich inc lusions (small islands) with a size of less than 10 nm. A preferential vert ical correlation of the small islands occurs for the 12 ML spacer thickness . With increasing spacer thickness, the number of the correlated small isla nds is reduced displaying a tendency to uncorrelated growth. (C) 2001 Ameri can Institute of Physics.