We demonstrate the effects of using an As2 source to fabricate self-organized InAs/GaAs quantum dot (QD) structures. QDs grown with As2 and As4 sources have narrow photoluminescence (PL) linewidths (22 and 20 meV, respectively) and their respective emissions at room temperature are 1.30 and 1.29 μm. QDs grown with an As2 source have a longer wavelength emission than those grown with an As4 source under all growth conditions. The density of QDs grown with an As4 source is larger and the dot size smaller than those of QDs grown with an As2 source. These results indicate that QDs grown with As2 are larger, resulting in a longer PL wavelength.