The intermittent illumination treatment by white light at elevated temperature is proved to be a convenient and efficient method for the improvement of the stability of hydrogenated amorphous silicon (a‐Si:H) films. The effect of the treatment on electrical properties, light‐induced degradation, and gap states of undopeda‐Si:H films has been investigated in detail. With the increase of cycling number, the dark‐ as well as photo‐conductivities in annealed state and light‐soaked state approach each other, presenting an unique irreversible effect. The stabilization and ordering processes by the present treatment can not be achieved merely by annealing under the same conditions. It is shown that the treatment proposed here results in a shift to higher values of the energy barriers between defects and their precursors, and hence an improved stability ofa‐Si:H films. ©1996 American Institute of Physics.