ON MOBILITY-FLUCTUATION ORIGIN OF 1/F NOISE

The bases and implications of models ascribing 1/f noise to the fluctuations in the number and mobility of the carriers are reviewed and compared, their symmetry and equivalence are shown and new results are proposed. It is proved that local and uncorrelated fluctuations in the mobility need variations in the total density of the carriers, which, however, do not affect the short-circuit current, and that they are due and equivalent to the fluctuations in the defect charges. These and other results are reached by determining in a general way the coupling equation between the local and the output fluctuations, and by finding through it that the short-circuit current fluctuations are given simply by the integral over the sample of the mobility variations or, in an equivalent way, of the fluctuations in the defect charges. The mobility variance for the various models is also computed and it is shown that, for some of them, it reaches values too high to be easily explained.