The photoluminescence (PL) spectra from modulated quantum well structures were observed. The modulated quantum well structure comprised a 4 monolayer (ML) modulated layer and an 18 ML GaAs layer between AlAs barrier layers. The modulated layer was grown by incorporating As into a Ga and Al mixture on an AlAs surface. The main peak energy of the PL spectra at 77 K showed a growth temperature dependence; a remarkable red shfit of the main peak energy was observed for samples grown at low temperature. The red shift of the PL peak energy indicates an increase in the effective width of the GaAs well. A rearrangement model of Ga and Al atoms on the AlAs surface during growth with As incorporation into the Ga and Al mixture is proposed to explain the growth temperature dependence of the PL peak energy.