Device grade hydrogenated polymorphous silicon deposited at high rates

Abstract

Hydrogenated polymorphous silicon (pm-Si:H) thin films have been deposited by plasma-enhanced chemical vapor deposition at high rate (8–10Å/s), and a set of complementary techniques have been used to study transport, localized state distribution, and optical properties of these films, as well as the stability of these properties during light-soaking. We demonstrate that these high deposition rate pm-Si:H films have outstanding electronic properties, with, for example, ambipolar diffusion length (Ld) values up to 290nm, and density of states at the Fermi level well below 1015cm−3eV−1. Consistent with these material studies, results on pm-Si:H PIN modules show no dependence of their initial efficiency on the increase of the deposition rate from 1 to 10Å/s. Although there is some degradation after light-soaking, the electronic quality of the films is better than for degraded standard hydrogenated amorphous silicon (values of Ld up to 200nm). This result is reflected in the light-soaked device characteristics.