Conductance fluctuations in undoped intrinsic hydrogenated amorphous silicon films prepared using several deposition techniques

Coplanar conductance fluctuations in a range of device quality undoped hydrogenated amorphous silicon (a-Si:H) films prepared using different deposition systems were measured in the temperature range of 440–505 K for frequencies from 2 Hz to 3 kHz. The 1/fα type noise spectra had two different power law dependencies, one at lower frequencies with slope α1 close to unity and a second region at higher frequencies with slope α2 around 0.60. The noise power density decreases with increasing temperature in the high frequency region, but only increases much less with temperature at low frequencies. The results indicate that the noise in undoped intrinsic a-Si:H films is due to two independent noise mechanisms operating simultaneously.