Voltage noises with power spectra of the form 1/$f^{\gamma }$ were studied in a series of custom and commercial p-channel metal-oxide-semiconductor field-effect transistors. Detailed measurements of the time-correlation functions indicated that the noise originated from a stationary and Gaussian source. The spatial correlation function, measured in devices made with extra voltage probes placed in the conduction channels, showed no measurable amount of correlation down to a distance of 7 μm, excluding the possibility of a diffusion mechanism for the noise. The results, combined with the experimental data on the dependence of the noise power spectra on the bias conditions, led us to establish a simple model based on a variation of the ‘‘McWhorter model’’ to account for the noise. Built into the model was an energy dependence of the trap concentration which in turn yielded a spatial dependence in the presence of a gate bias. This model explained quantitatively the experimentally observed change in the exponent γ of the noise spectrum as the gate bias was varied. It was then meaningful to compare the experimental and computed noise powers at a single, fixed frequency.

• Received 10 May 1985

DOI:https://doi.org/10.1103/PhysRevB.33.4898