Long-range potential fluctuations and1/fnoise in hydrogenated amorphous silicon

Abstract

We present a microscopic theory of the low-frequency voltage noise ͑known as ''1/f '' noise͒ in m-thick films of hydrogenated amorphous silicon. This theory traces the noise back to the long-range fluctuations of the Coulomb potential created by deep defects, thereby predicting the absolute noise intensity as a function of the distribution of defect activation energies. The predictions of this theory are in very good agreement with our own experiments in terms of both the absolute intensity and the temperature dependence of the noise spectra.

New experimental evidence for the role of long-range potential fluctuations in the mechanism of 1/f noise in a-Si:H

“…We present new experimental tests of our recent theoretical proposal [1] explaining the origin of low frequency resistance noise in hydrogenated amorphous silicon (a-Si:H). Usually, this kind of noise has a spectral shape close to 1/f, where f is frequency.…”

“…We test the above prediction on a pip structure, grown in the same reactor and under similar conditions as the nin structure studied in Ref. [1].…”

“…[1] with the escape and the capture of carriers, then the 1/f noise spectrum should not depend on the substitution of hydrogen with its heavier isotope deuterium -subject of the other test presented in this work…”

“…It also yields the prefactor in front of the 1/f frequency dependence. In the original work [1] we studied 1/f noise in the sandwich structure consisting of electron doped -undoped -electron doped layers (nin structure) of a-Si:H. In that structure the resistance noise originated from the middle of the undoped layer, where electrons are the majority carriers.…”

“…In Ref. [1], it was assumed that the distribution of the potential barriers for electron escape from deep defects is related to the medium range disorder of the local potential around the defects. This type of disorder should not be much different for the holes with respect to the valence band edge E V as compared with that of the electrons with respect to the conduction band edge E C .…”