InAs/GaAs quantum dot density variation across a quarter wafer when grown with substrate rotation

Variations in quantum dot density across 16 different 2 in quarter wafers have been studied. The InAs/GaAs quantum dots (QDs) were grown on n-type GaAs(0 0 1) substrates by molecular beam epitaxy and studied by scanning electron microscopy (SEM). The SEM study reveals large variations in QD density and size homogeneity across the 16 quarter wafers. A representative sample was studied in great detail. For this sample the QD density is lower in the middle of the 1/4-wafer than along the rims, and also considerably higher in one of the corners compared to the other two corners. The QD diameters and size homogeneity are reduced in areas with high QD density compared to areas with low QD density. The above variations are believed to be mainly due to temperature variations across the 1/4-wafer during growth of the QDs.