Study of 1/f noise in hydrogenated amorphous silicon thin films

We report a study of flicker noise in n-type hydrogenated amorphous silicon (a-Si:H) resistive devices from room temperature to about 420 K. The device was first annealed at 450 K and then cooled to room temperature at a rate of ∼0.5 K s^-1. The voltage noise power spectra and the conductance of the device were characterized from room temperature to 420 K. The experiment was then repeated with the device annealed again and subsequently cooled at a rate of ∼0.02 K s^-1. The Arrhenius plots of the voltage noise power spectrum, S_v(f), are found to exhibit thermal equilibration processes commonly observed in a-Si:H materials. Characterization of the bias dependencies of the noise show that S_v(f) deviates from an P dependence indicating that the noise arises from a non-linear process. Also, S_v(f) is proportional to R^p where p is dependent on the temperature and the cooling process of the device. Our experimental data provide strong evidence that the flicker noise originates from hydrogen motion within the material. The process appears to cause fluctuations in the device conductance by modulating the percolation path of the carriers.