In this paper it is presented the study of trap-filling time in a GaAs single crystal and InAs Self-assembled quantum dots (SAQDs), using the analysis of the photoreflectance (PR) spectra measured at room temperature. The SAQDs were grown on a GaAs substrate by molecular beam epitaxy (MBE), and GaAs sample is a commercial single crystal. The PR spectra were measured varying the chopper frequency from 80 Hz to 3000 Hz. From the analysis of these PR spectra, it was obtained the dependence of the PR signal intensity with the modulation frequency. By fitting these experimental data, it was determined that the presence of the SAQDs increases the value of .