Noise of junction devices

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Abstract
The conduction and noise mechanisms and the relevant models are quite different and more complex for bipolar than for unipolar media and devices. A new general approach to p-n junction noise, which ascribes its origin to the charge fluctuations of the defect centers, is proposed. For the single defect the relaxation time, the Langevin noise sources, and the modulation of the generation-recombination (GR) current across the neighboring defects, are computed according to a previous model by means of the Shockley-Read-Hall theory, the Schottky theorem, and the Poisson equation. The interactions of the charge and current fluctuations of the single defect with the output short-circuit currents are then expressed by means of proper charge and current coupling coefficients. In their turn, these are computed in closed general form for a long junction, for both neutral and space-charge regions, by means of continuity and Poisson equations and using a new method which reduces the noise coupling problems from three to one dimension. In this way, a general expression of the noise spectrum of the junction, which holds good for any doping and bias voltage and for any frequency up to the reciprocal of the lifetime of the carrier, is obtained.