Doped microcrystalline silicon oxide alloys for silicon-based photovoltaics: Optoelectronic properties, chemical composition, and structure studied by advanced characterization techniques

Doped microcrystalline silicon oxide (mu c-SiOx: H) alloys attract significant attention as a functional material in photovoltaic devices. By using various advanced characterization methods, we have studied the relationship between optoelectronic properties, chemical composition, and structure of p-type mu c-SiOx: H deposited by plasma enhanced chemical vapor deposition (PECVD). For a wide range of compositions with varying oxygen content, we show that the dominant components are Si and a-SiO2, while the fraction of suboxides is minor. The mu c-SiOx: H material with sufficient oxygen content (x = 0.35) exhibits an enlarged optical gap E-04> 2.2 eV and sufficiently high dark conductivity > 10(-6)S cm(-1); the crystalline silicon fraction has a filament-like shape (with a typical width of around 10 nm) forming a branch-like structure elongated in the growth direction over several hundreds of nanometers. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim