A theory of capacitance-voltage measurements on amorphous silicon Schottky barriers

Abstract

The frequency-dependent differential capacitance of an amorphous silicon Schottky barrier is calculated as a function of d.c. bias using a simple model of the Schottky barrier and an assumed form for the density of electronic states, n(E), of the silicon. The results show that at frequencies as low as 1 Hz the capacitance of the Schottky barrier can be considerably different from the static capacitance because of the slow response of the electron occupancy of localized states. A detailed development of the theory is presented to demonstrate the way in which information on n(E) is contained within the capacitance-voltage (CV) results. The deduction of n(E) from the CV results is possible if the static capacitance is known but, when relaxation effects are significant, there appears to be no simple way of obtaining n(E) directly.