Generalization of Nyquist-Einstein relationship to conditions far from equilibrium in nondegenerate semiconductors

We present for the first time an exact decomposition procedure for the current spectral density in the presence of generation-recombination mechanisms. The correct microscopic analysis shows that the cross correlation between velocity and number fluctuations plays an essential role in the noise properties of semiconductors. This, in turn, yields a generalization of the Nyquist-Einstein relationship in the presence of an applied electric field when statistical generation and recombination mechanisms are active.