The microstructure and optical properties of p-type microcrystalline silicon thin films characterized by ex-situ spectroscopic ellipsometry

Ex-situ spectroscopy ellipsometry (SE) was applied on the ~ 25 nm thick p-type hydrogenated microcrystalline silicon (p-μc-Si:H) thin films deposited by very high frequency plasma enhanced chemical vapor deposition. Several optical models were built and compared with each other for ex-situ SE data analysis considering both the oxide surface and the heterogeneous bulk condition to reveal the material microstructure and obtain optical function. The SE results imply that the p-μc-Si:H has both an oxide rich surface and the bulk with a flexible amorphous phase, the bandgap of which depends on the gas doping ratio (DR) of B2H6/SiH4. At the same time, we were able to distinguish p-μc-Si:H materials in crystalline volume fraction by ex-situ SE as confirmed by Raman scattering. In this way, we showed the effect of DR on μc-Si:H thin films in microstructural and optical properties.