Conductance Fluctuations in Hydrogenated Amorphous Silicon

Measurements of co-planar resistance fluctuations are reported for n-type doped hydrogenated amorphous silicon over the temperature range 190 < T < 450 K. The spectral density of the fluctuations obey a 1/f frequency dependence over the frequency range 1 < f < 10^3 Hz. The noise power displays a non-linear dependence on the applied DC current, that is the noise power S _{I} ~ I^{rm b}, where 1.0 < b < 2.5. Random telegraph switching noise is observed with fluctuations as large as deltaR/R ~ 10^{-2} in samples with volumes of 10^{-7} cm^3. Statistical analysis of the noise power spectra show the fluctuations to be strongly non-Gaussian. The noise power magnitude and frequency dependence are both time dependent. These results suggest that cooperative dynamics govern the conductance fluctuations, and are discussed in terms of models for noise in composite and inhomogeneous materials.