1/f-noise study of undoped intrinsic hydrogenated amorphous silicon thin films

Conductance fluctuations in four samples of undoped intrinsic hydrogenated amorphous silicon (a-Si:H) were measured in the temperature range of 450 K to 500 K and for frequencies from 2 Hz to 3 kHz. The noise spectra divide i nto two regions that each fit a 1/f(alpha) power law but with different slo pe parameters alpha and different temperature dependences. At low frequenci es, alpha is greater than unity and increases with temperature. At high fre quencies, alpha is near 0.6 and temperature independent, but the noise magn itude decreases rapidly with temperature. We infer from the different depen dences on temperature that the noise is generated by two independent mechan isms operating simultaneously in a-Si:H. We also observe that the 1/f noise exhibits a quadratic dependence on bias current and Gaussian statistics. [ S0163-1829(99)04327-1].