Influence of hydrogen on the properties of titanium doped hydrogenated amorphous silicon prepared by sputtering

Titanium doped hydrogenated amorphous silicon (a-Si:Ti(H)) with different gas ratio (rH = H2/Ar) were prepared by rf co-sputtering in mixture of hydrogen and argon, with fixed Ti content. The optical, structural and optoelectronic properties of the prepared a-Si:Ti(H) were investigated systematically by Spectroscopic Ellipsometry (SE), photo/dark conductivity and Fourier Transform Infrared (FTIR) measurements. With hydrogen introducing into a-Si: Ti network, the optical bandgap of a-Si:Ti(H), dark current and photosensitivity (Ratio of photo conductivity to dark conductivity) improved. However, although detectable photosensitivity occurs at rH of 0.3, it has relatively larger microstructure factor R and less compact structure compared with rH of 0.2 and 0.4. It is found that unintended oxygen content plays an important role in improving photosensitivity, and the relationship between microstructure, optical and photosensitivity of a-Si:Ti (H) was discussed in detail.