Effect of HCl addition on the properties of p-type silicon thin films during hot-wire chemical vapor deposition

The effect of HCl addition on the structural, electrical, and optical properties of p-type silicon films, prepared by hot-wire chemical vapor deposition (HWCVD), was investigated. As the ratio of HCl to SiH4 increased, the amount of amorphous silicon decreased and the crystalline volume fraction increased in the deposited film. To investigate the effect of HCl addition on the deposition behavior in the initial stage, the transmission electron microscope (TEM) grid membrane was exposed for 10 s using a shutter above the grid membrane during HWCVD and the grid membrane was observed by TEM. When HCl was not added, a continuous film was observed on a grid membrane, consisting of crystalline nanoparticles embedded in an amorphous matrix whereas when HCl is added, isolated individual crystalline nanoparticles without amorphous silicon were observed. The HCl addition increased the dark conductivity of films by about 3 orders of magnitude but decreased the optical band gap slightly.