Photo-induced effects in Ge-Ga-Se films

We investigated photo-induced effects in Ge-Ga-Se films. It was found that, thermal annealing causes the increase of the bandgap in the as-prepared films, and all three annealed films show photodarkening (PD) behavior with light illumination but the change of optical bandgap is minimum in Ge25 film. Such PD behavior can be recovered by reannealing of the film. The kinetic process of Tf/Ti exhibits part recovering of PD during the cycle of laser on and off. Moreover, no obvious structural change can be observed in the Raman spectra of the films at different states, especially in that of Ge25 film.