Conductance fluctuations in a-Si:H: Effects of alloying and device structure

Abstract

We present measurements of conductance noise in undoped a-Si:H and a-SiGe: H thin films in both a transverse and coplanar electrode geometry. For a-Si:H with coplanar electrodes, the noise spectrum is not a pure f-α power law but consists of two linear regions with different slope parameters α. The spectral shape and its temperature dependence are similar for all samples, regardless of the growth technique. Adding Ge results in qualitatively similar spectra; however, α at high frequencies and the temperature dependence are altered. For both a-Si:H and a-SiGe:H with transverse electrodes, the noise spectra are pure f-α power laws, and α decreases with the Ge content.