Nature of the dominant deep trap in amorphous silicon nitride

We observe a strong correlation between changes in the density of paramagnetic silicon-``dangling-bond'' centers and changes in the space-charge density in amorphous silicon nitride films subjected alternately to positive and negative charge injection and optical illumination. Our results provide, for the first time, direct experimental evidence associating a specific point defect with the trapping phenomena in amorphous silicon nitride. We also demonstrate both directly and for the first time the amphoteric nature of the silicon nitride silicon-dangling-bond center.