Influence of Light-Soaking in Undoped Polycrystalline Silicon Films from SiCl4/H2

The stability of pc-Si films under long-time illumination was studied. The films were fabricated at low temperature of 250degC by plasma-enhanced chemical vapor deposition technology from SiCl₄ /H₂. The light soaking for 720 min in vacuum was carried out using white light of an intensity of 100 mW/cm². The light-induced effects were monitored by measuring the changes in the photoconductivity and dark conductivity. The experimental results indicate that light-soaking degradation phenomenon doesn´t exit in the pc-Si films, which almost appears in all a-Si films. During long-term light irradiation, the photoconductivity is increasing all along until saturation. The phenomenon is similar to the persistent photoconductivity effect observed in the a-Ge films. Furthermore, the light-induced changes of conductivity depend on hydrogen dilution ratio. The persistent photoconductivity effect appeared in pc-Si films maybe relate to the material microstructure. Comparing with amorphous silicon films, pc-Si films have high crystallinity. Besides, we think chlorine element plays a important role