The dependence of the optical properties on the temperature in multiple-stacked InAs/GaAs quantum dots (QDs) grown on (001)-oriented GaAs substrates by using molecular beam epitaxy Was investigated. The periods of the photoluminescence (PL) spectra at low temperature for the sample with a three-monolayer (ML) InAs seed layer and two 1.8-ML InAs layers showed doublet peaks. The double peaks originated from interband transitions from the ground state subband to the ground heavy-hole band for QDs with a bimodal size-distributation, which was verified by using transmission electron microscopy measurements. The temperature-dependent PL spectra are discussed in terms of the inhomogeneous size distribution of the QDs and the carrier repopulation process. The present results can help to improve the understanding of the dependence of the optical properties on the temperature in multiple-stacked InAs/GaAs QDs. (C) 2003 Elsevier B.V. All rights reserved.