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

Doped microcrystalline silicon oxide (μc-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 µc-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 μc-SiOx:H material with sufficient oxygen content (x = 0.35) exhibits an enlarged optical gap E04 > 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.