Noise and admittance of the generation—Recombination current involving SRH centers in the space-charge region of junction devices

A collective transport-noise theory is given for the effects caused by generation-recombination current via traps in the space-charge region of a p-n junction. Langevin noise sources are added to the standard kinetic equations, which are subsequently solved for the current noise. No hypotheses are made on the coupling of the g-r current to the external circuit. In particular, Ramo's theorem does not apply, though similar transport factors emerge automatically as a consequence of the inclusion of displacement current. With the assumption that the free carrier transit times are very short, exact agreement with Lauritzen's [3] previous results, based on a probabilistic approach, is found. In addition, the admittance is computed from the same equations and is shown to be frequency dependent, contrary to standard assumptions made for the computation of emitter efficiency. Consistency with Nyquist's theorem is obtained for the low and high frequency regime. The noise reduction factors for forward biased junctions are discussed.