We investigated the electric field dependence of photoluminescence (PL) spectra in four kinds of GaAs/AlAs multi-quantum
well (MQW) structures. Only one of them exhibited various PL spectra in spite of having a similar sample
structure in the MQW. The PL spectra reveal several signals in the shorter wavelength region due to the combination
effect of interface roughness and Γ-Χ scattering. We also estimated the carrier densities of excited states by observed PL
intensities and calculation of overlap integrals of wavefunctions between electron and heavy hole states. The observation
of PL signals from excited states in the MQW provides fruitful information on carrier densities and structural
imperfection of MQWs.