Interfacial Properties of a-Si:H/a-SiNx:H Multilayers Studied by electroabsorption Spectroscopy

By using electroabsorption method, we find that the built-in field (~10⁵ V.cm^-1) in the a-Si sublayers of a-Si:H/a-SiN_x:H multilayers points towards the sample surfaces. We ascribe the internal field to the asymmetric distribution of defect states which exist primarily in the silicon side of the silicon-on-nitride interfaces, owing to the large repellent lattice stress there. We also find that the built-in potential depends strongly on x, with a maximum value near x = 1.0. We intend to explain it as a result of structural softening as more N atoms are introduced into Si networks in the range of x > 1.0.