Conductance fluctuations in hydrogenated amorphous germanium

Measurements of conductance fluctuations in undoped hydrogenated amorphous germanium (a-Ge:H) find power spectra that vary with inverse frequency (1/f) that are characterized by non-Gaussian statistics. The non-Gaussian aspect of the 1/f noise is reflected in (1) histograms of the noise power per octave that are described by lognormal distributions, (2) power-law second spectra, and (3) strong correlations of the noise power in frequency-space. In contrast, measurements of current fluctuations in polycrystalline germanium thin films find 1/f noise with Gaussian statistics. These results are discussed in terms of a model of filamentary conduction, where the filament structure and conductance in a-Ge:H are modulated by hydrogen motion.