Self-assembled laterally aligned InAs quantum dot molecules (QDMs) were grown on GaAs substrates by metal-organic chemical vapor deposition. The effects of growth temperature and InAs coverage on the structural and optical properties of QDMs are investigated by using atomic force microscopy and photoluminescence. It is found that through appropriately selecting growth parameters, QDMs composed of two closely spaced InAs quantum dots (QDs) are formed, and the distance between the two QDs can be controlled. Moreover, a redshift of emission wavelength attributed to the formation of QDMs is observed. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3516010]