The dependence of the integrated photoluminescence on the excitation power intensity in Al(0.3)Ga(0.7)As/GaAs multi quantum well is studied. Four peaks are found in the photoluminescence spectra, which are corresponding to the four quantum wells in the sample. The temperature dependence of the exponent alpha of the power law shows peculiar behavior for the quantum well of width 11.2 nm (peak C). The value of the exponent alpha exceeds the quadratic value predicted by the steady state model near room temperature. All other peaks shows linear dependence in the low temperature range which switches to super linear in the high temperature range with values of alpha less than 2. Carriers thermal capture and re-trapping is discussed. The presented results are a sign of thermal dissociation of exciton in quantum well near room temperature. The peculiar behavior is attributed to the excess flow of the charge carriers to this QW by thermal escape from other QWs, and also due to excess free carriers because of exciton dissociation.