Role of Ar dilution of SiH4/PH3 gas mixture on PECVD based film growth process, hydrogen bonding configuration, and optical properties of n-type a-Si:H thin films

Abstract

Amorphous silicon is considered as one of the most promising materials for solar cell applications due to its enhanced optical absorption, high temperature coefficient of resistance, controllable forbidden-band gap, and to reduce the costs of solar panels. In this study, we took notice of the film growth, hydrogen bonding configuration, and optical properties of the phosphorus doped a-Si:H films by varying the dilution of silane using argon gas. Argon gas is a chemically non-reactive gas, but it affects the percentage of silicon atoms during processing. A change in growth process and microstructure factor with varying Ar gas flow is observed, which causes changes in the optical properties of P-doped a-Si:H films. The proportion of SiH bonding rises with increasing argon flow rate, as seen by the infrared-absorption spectra. According to optical tests of the films, the refractive index of the films rises with the Ar flow rate, whereas the band gap Eg decreases. Dilution of SiH4 results in a good-quality film with increased optical conductivity. We established experimental proof of a correlation between band gap and refractive index and compared it with previously reported theoretical models. An investigation into the band gap's dependency on Urbach energy revealed its linearity.