We have investigated the evolution of structural and optical characteristics in self-assembled InAs/GaAs quantum dot (QD) structures with cap layers thinner than or comparable to QD height. Based on cross-sectional QD profiles of atomic force microscopy obtained from incompletely capped samples, we have suggested that the anisotropic image is not a QD structure per se but a complex one combined by QD and sidewall coverage, and schematic models have been illustrated for the structural evolution related with the capping process. As evidence supporting the structural characteristics, the photoluminescence emission spectra showing a crossover of red-to-blue shift of confined QD sublevels at a critical coverage of 5 nm close to average QD height are presented. We have proposed energy band diagrams framed by effective potentials of surface barrier that can explain the energy shift phenomena. (c) 2005 Elsevier B.V. All rights reserved.