Doping effects on conductivity and electron spin resonance in post-hydrogenated polycrystalline silicon

Abstract

The effects of plasma hydrogenation on the electrical properties and electron spin resonance (ESR) are investigated for phosphorus and boron doped polycrystalline silicon films produced by annealing from chemical vapor deposited amorphous silicon. In lightly doped films, the dark conductivity and photoconductivity increase with hydrogenation. The photoconductivity also increases with increasing doping ratio. These increases of the dark conductivity and photoconductivity correspond well to a decrease of ESR spin density due to dangling bonds. In hydrogenated films doped with phosphorus or boron, it is found that the dark conductivity first decreases with increasing doping ratio, and then rapidly increases. These results for the electrical properties and ESR are discussed in terms of the two-phase model in which crystallites with surface bandbending and a damaged layer between the crystallites are included. As a consequence the electrical properties are indicated to have a close relation to the density of dangling bonds in the damaged layer, and the dark conductivity and photoconductivity are controlled by surface conduction of crystallites and a short lifetime of photogenerated carriers in the damaged layer, respectively, depending on the density of dangling bonds. The temperature dependence of the photoconductivity is also discussed based on this model.