Atomic force microscopy (AFM) measurements were carried out to investigate the formation of CdTe quantum dots (QDs) grown on GaAs substrates by using molecular beam epitaxy. The AFM images showed that uniform CdTe QDs were formed on GaAs substrates due to the large lattice mismatch between the CdTe QDs and the GaAs substrate. The size and the density of the CdTe QDs were varied by changing the thickness and the substrate temperature. The formation behavior for the CdTe QDs on the GaAs substrate is in reasonable agreement with a Volmer-Weber (V-W) growth mode. The size and the density of the CdTe QDs grown on the GaAs substrate by using the V-W growth mode are compared with those of the CdTe QDs grown on the ZnTe buffer layer by using the Stranski-Krastanow mode. The present results can help improve understanding of the formation and the structural properties of CdTe QDs directly grown on GaAs substrates. (c) 2006 Elsevier B.V. All rights reserved.