An improved field-effect analysis for the determination of the pseudogap-state density in amorphous semiconductors

Abstract

A method is described for determining the gap-state density N(ε) of an amorphous semiconductor from field-effect data, in which no assumptions are made about the form of the band-bending in the semiconductor. The problem is reduced to three successive integrations over an assumed N(ε) by change of variable from depth x to voltage V, and the best fit to the experimental data is obtained by iteration of the assumed state density. The method is shown to be no less rigorous and considerably more economical than the recent analysis of Goodman, Fritzsche and Ozaki (1980). In addition, we demonstrate an experimental means of determining flat-band conditions to an accuracy of 1/2 kT of band bending, by finding the value of V _g for which (kT/e)d log I _SD/dV _g is independent of temperature.