4. Hydrogenated amorphous silicon (SiaH)

Amorphous silicon can be easily processed into thin films by depositing it at low temperatures (< 300°C) on a single-crystal or amorphous substrate (e.g. a glass plate) using vacuum evaporation or sputtering. For a long time, this material had no practical application: its resistivity is very high (much higher than that of intrinsic single-crystal silicon, since its mobility band gap is of the order of 1.7 eV), and it was impossible to modulate its resistivity by adding dopant impurities