ANISOTROPIC EXCESS NOISE WITHIN A-SI-H

Anisotropic excess noise is reported for hydrogenated amorphous silico n. The simple act of reversing the bias on small samples of a-Si:H lea ds to startling changes in the noise. These large variations are obser ved for samples where the excess noise features a random telegraph swi tching (RTS) noise component in addition to 1/f noise. These samples d isplay non-ohmic characteristics. Other samples which display no obser vable RTS noise, however, show little change in the 1/f noise followin g a reverse in bias. These results show that the substantial RTS withi n a-Si:H is associated with anisotropic effects, such as a graded band gap. This behaviour is observed in a-Si:H material grown by both the plasma enhanced chemical vapour deposition and the rf sputtered deposi tion methods.