Optical properties of InAsN/InGaAs quantum wells on InP grown by gas source molecular beam epitaxy have been investigated by photoconductivity measurements. It is found that the persistent photoconductivity (PPC) does exist in this nitrogen compound material. Through a detailed study of the dependence of the PPC effect on excitation photon energy, temperature, decay kinetics and nitrogen composition, we point out that the origin of the PPC effect arises from the metastability of deep level centers. In different charge states, the defect centers can undergo a large lattice relaxation which creates an energy barrier to prevent the photoexcited carriers from returning to the original states, and thus the PPC occurs. We find that the obtained energy barrier increases with nitrogen composition.
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