Unique correlation of the Fermi energy with the metastable defect density in amorphous silicon

This paper reports an empirically based correlation between the metastable defect density and the value and temperature dependence of the Fermi energy in undoped hydrogenated amorphous silicon. According to this correlation, to specify two of the three quantities: Fermi energy, defect density, and temperature, is to specify the third, independent of the history of the sample. Almost 300 measurements of dark conductivity over a wide range of defect densities and temperatures, obtained in the course of measuring the kinetics of optical degradation of amorphous silicon at four temperatures, were subjected to analysis. A detailed empirical summary of these data is given, since their relevance extends beyond this present work. A model with two different types of multivalent defects whose relative density changes with total defect density is the simplest model consistent with the data.