Effect of the hydrogen bonding and content on the opto-electronic properties of radiofrequency magnetron sputtered hydrogenated amorphous silicon films

Infrared absorption and optical transmission combined with photothermal deflection spectroscopy experiments have been used to study the effect of the hydrogen bonding and content on the opto-electronic properties of hydrogenated amorphous silicon (a-Si:H) films prepared by radiofrequency magnetron sputtering at high deposition rates (11–15 Å/s), at the same substrate temperature (250°C) and with different H2 dilution percentage. The results indicate that the electronic properties, in terms of density of defects and disorder, are dependent on both the relative proportion of the isolated monohydride Si–H bonds and the presence in the films of structural inhomogeneities, while the optical gap is found to be rather controlled by the total bonded hydrogen content CH. Optimized films with quite low density of defects and disorder and which contain the highest proportion (∼38%) of isolated monohydride complexes are obtained. An increase in the proportion of the polyhydride and/or the clustered monohydride configurations gives rise to more gas states and disorder and favors the formation of higher structural inhomogeneities such as voids.