Weakly non-Gaussian processes in a-Si:H conductance noise

Measurements of fourth-order correlations of the flicker noise in hydrogenated amorphous silicon (a-Si:H) thin films reveal state-dependent contributions from non-Gaussian noise processes. Such processes appear only as weak features superimposed on a Gaussian background in power spectral plots and octave correlations. Applying the recently optimized ``second spectrum'' technique yields a sensitive measure of the extent of correlations between fluctuators which are found to depend upon their phase correlations only. The effects upon the noise of annealing and aging the sample as well as the time evolution of the second spectrum upon application of an electrical field suggest that sample microstructure and field-induced processes may play roles in inducing correlations among fluctuators.