InGaAsP/InP multiple quantum wells with quantum well intermixing have been prepared by impurity-free vacancy disordering.The luminescent characteristics were investigated using photoluminescence and photoreflectance,from which the band gap blue shift was observed.Si_3N_4,SiO_2 and SOG were used for the dielectric layer to enhance intermixing from the outdiffusion of group III atoms.All samples were annealed by rapid thermal annealing.The results indicate that the band gap blue shift varies with the dielectric layers and the annealing temperature.The SiO_2 capping with an InGaAs cladding layer was successfully used to induce larger band tuning effect in the InGaAsP/InP MQWs than the Si_3N_4 capping with an InGaAs cladding layer.On the other hand, samples with the Si_3N_4-InP cap layer combination also show larger energy shifts than that with SiO_2-InP cap layer combination. InGaAsP / InP multiple quantum wells with quantum well intermixing have been prepared by impurity-free vacancy disordering. The luminescent characteristics were investigated using photoluminescence and photoreflectance, from which the band gap blue shift was observed. Si_3N_4, SiO_2 and SOG were used for the dielectric layer to enhance intermixing from the outdiffusion of group III atoms. All samples were annealed by rapid thermal annealing. the results that the band gap blue shift varies with the dielectric layers and the annealing temperature. The SiO 2 capping with an InGaAs cladding layer was successfully used to induce larger band tuning effect in the InGaAsP / InP MQWs than the Si_3N_4 capping with an InGaAs cladding layer. On the other hand, samples with the Si_3N_4-InP cap layer combination also show larger energy shifts than that with SiO_2-InP cap layer combination.