engleski

Effects of Light Soaking on Amorphous Silicon Thin Films

We have studied the effect of light soaking with UV, white and sub-gap light on intrinsic a-Si:H films and compared it to the effect of thermal annealing in the dark. It is shown that the light soaking of the films in the air did not affect hydrogen concentration from Si-H bonds and at same time oxidation of the films is observed. It suggests that the oxygen incorporation was due to broken backbonds to Si-H which are very likely weak bonds. Moreover it is found that while subgap irradiation did not produce oxidation white and UV light did, while UV light caused even minor Si-H bonds breaking. Vacuum annealing at 100 C in the dark on the other hand caused hydrogen redistribution enhancing thus Si-H bond concentration and recovering broken bonds. We have shown that our a-Si:H samples may contain oxygen, when produced in specific conditions. Light soaking and particularly UV light induces hydrogen release from Si-H bonds, which in turn stimulates oxygen redistribution. It has been also shown that light soaking creates defects, which introduce deep levels that are attributed to the oxygen presence. The effects of light soaking are shown to be dependent on the hydrogen content in the sample. Moreover the effects are much more pronounced in low-hydrogen samples.

amorphous silicon; p-i-n photodiode; thin films; defects

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