The impact of processing conditions and post-deposition oxidation on the opto-electrical properties of hydrogenated amorphous and nano-crystalline Germanium films

Low-cost multijunction photovoltaic devices are the next step in solar energy revolution. Adding a bottom junction with low bandgap material through plasma enhanced chemical vapor deposition (PECVD) processing could potentially provide low-cost boost conversion efficiency. A logical candidate for this is germanium. In work we investigate growth of PECVD processed hydrogenated amorphous/nano-crystalline germanium (a/nc-Ge:H), by characterizing over 100 samples, wide range pressures, powers, temperatures and GeH4 dilution hydrogen, using elemental analysis, vibrational analysis opto-electrical properties. We have identified small window which nc-Ge:H films reproducibly. also report on strong correlation between refractive index presence- extent post-deposition oxidation. Notably, oxidation generally increased photoresponse films, as it results decrease room temperature ?d 1-3 orders magnitude. However, an increase therefore impedes development material. The lowest E04 about 1.1eV, ETauc 0.9eV ?ph/?d 3.4.