Heterogeneities in hydrogenated amorphous silicon

The heterogeneities present in hydrogenated amorphous silicon (a-Si:H) give rise to long range potential fluctuations, and therefore play an important role in controlling its electronic properties. In addition, the light induced metastability (Staebler-Wronski effect) and the metastability caused by thermal quenching, appear to be related to the movement of hydrogen and therefore to heterogeneities. Here, the author uses the sub-band gap absorption and thermopower measurements to obtain information about: the potential fluctuations present in a-Si:H. The author finds that these potential fluctuations increase upon light soaking, but are not affected much by thermal quenching. Implications of these results for the stability of a-Si:H based devices are discussed.