Microcrystalline silicon films were deposited using the plasma enhanced chemical vapor phase deposition system and SiCl4/H2 gas source. We investigate the evolution of the dark conductivity of the fabricated films afte r a brief exposure to light or under DC bias. Raman spectra measurements indicat e that the volume fractions of crystalline phase for all samples are over 70%. T he measurement of dark resistance reveals the existence of weak persistent photo conductivity in our samples. Under DC electric field, it is found that the dark conductivity increases slowly with time and a restoration process occurs once th e field is reversed. This behavior depends on the DC bias level and the measurem ent temperature and can be explained by a heterojunction barrier model. It is su ggested that the spatial separation and redistribution of charge carriers under applied conditions and the potential barrier associated with inhomogeneity are r esponsible for the observed phenomena.