Highly conductive p-type nanocrystalline silicon films deposited by RF-PECVD using silane and trimethylboron mixtures at high pressure

Abstract

In this paper we present a study of boron-doped nc-Si:H films prepared by PECVD at high depositionpressure (>4 mbar), high plasma power and low substrate temperature (<200 C) using trimethylboron (TMB) as a dopant gas. The influence of deposition parameters on electrical, structural and optical propertiesis investigated. We determine the deposition conditions that lead to the formation of p-type nanocrystallinesilicon thin films with very high crystallinity, high value of dark conductivity (>7 (U cm)1) andhigh optical band gap (>1.7 eV). Modeling of ellipsometry spectra reveals that the film growth mechanismshould proceed through a sub-surface layer mechanism that leads to silicon crystallization.The obtained films are very good candidates for application in amorphous and nanocrystalline siliconsolar cells as a p-type window layer.