Optical properties of evaporated poly-Si thin-films on glass

Abstract

The optical properties of boron- and phosphorus-doped polycrystalline silicon films with light (~ 1 × 10 16 cm −3), moderate (~ 5 × 10 17 cm −3) and heavy doping (~ 1 × 10 19 cm −3) were investigated in this work. The films were prepared by solid-phase crystallization of evaporated amorphous silicon films on borosilicate glass. Tauc–Lorentz models with one or two oscillators were used to model both reflection and transmission data collected by a spectrophotometer over the wavelength range of 400 nm–2000 nm. The results indicate that the crystal quality of the films is improved by phosphorus doping, while boron has a negligible impact on the crystal quality. The poly-Si films exhibit greater absorption than c-Si for visible wavelengths. This enhanced absorption is believed to be associated with defected a-Si material at the grain boundaries and intra-grain defects.