Bias stress-induced instabilities in amorphous silicon nitride/hydrogenated amorphous silicon structures: Is the ‘‘carrier-induced defect creation’’ model correct?

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Abstract
The effects of positive and negative bias stress on hydrogenated amorphous silicon nitride/hydrogenated amorphous silicon (a‐SiNx:H/a‐Si:H) structures are investigated as a function of stress time, and stress temperature. It is shown that bias stress induces a parallel shift of the capacitance voltage (C‐V) characteristics. The direction of the C‐V shift depends on the sign of the applied stress voltage, while the magnitude of the C‐V shift depends on stress time and temperature in a manner which is identical to that observed in a‐Si:H thin‐film transistors. In addition, it is shown that positive bias stress increases the number of localized states in the a‐Si:H mobility gap, but negative bias stress does not. However, the observed increase cannot account for the corresponding C‐V shift. These results lead us to conclude that the C‐V shift is not induced by dangling bond defects in a‐Si:H but rather by carrier trapping in the insulator.