EXPLORATORY OBSERVATIONS OF RANDOM TELEGRAPHIC SIGNALS AND NOISE IN HOMOGENEOUS HYDROGENATED AMORPHOUS-SILICON

Noise measurements on unhydrogenated and hydrogenated rf sputtered intrinsic amorphous silicon reported by D'Amico, Fortunato, and Van Vliet [Solid-State Electron. 28, 837 (1985)] have 1/f and Lorentzian spectra, respectively. Similar noise measurements on glow-discharge deposited hydrogenated amorphous intrinsic silicon reported by Bathaei and Anderson [Philos. Mag. B 55, 87 (1987)] gave a 1/f m spectrum with 0.7<m<1. Even more recently Ley and Arce [Proc. MRS Symposium, San Diego (1989)] have reported random telegraph signals in a-Si@B: H/a-Si 1-xNx@B: H double barrier structures. The associated noise was a Lorentzian noise spectrum. In this paper the first observation of random telegraph signals in notionally homogeneous heavily doped (p+) glow-discharged-deposited amorphous silicon is reported. It was found that the current passing through the sample fluctuates between two easily identifiable levels with the periods of fluctuations separated by a quiescent period. The occurrence of these fluctuations is unpredictable but the current noise spectrum obtained during quiescent periods is Lorentzian, probably indicative of a generation-recombination process. Noise measurements are not possible at higher biases (>105 V/cm) as the current fluctuates chaotically and this is also the prebreakdown regime of the sample.