CONDUCTANCE FLUCTUATIONS IN DOPED HYDROGENATED AMORPHOUS-SILICON

Conductance fluctuations in n-type doped hydrogenated amorphous silicon (a-Si:H) films are described. The spectral density of the coplanar current fluctuations has a 1/f frequency dependence for frequency f from 1 < f < 10(4) Hz over the temperature range 300 < T < 450 K. The noise power density displays a power-law dependence on the dc current passing through the film, with a temperature-dependent power-law exponent. Random telegraph switching noise is observed in coplanar current measurements in samples with effective volumes of 10(-6) to 10(-7) cm3 with fluctuations as large as DELTAR/R approximately 1%. Statistical analysis of these fluctuations indicates that the 1/f noise is strongly non-Gaussian, suggestive of cooperative interactions between fluctuators. A model is proposed in which the noise is dominated by inhomogeneous current paths whose local conductivity is modulated by bonding rearrangements enabled by hydrogen motion.