The generation-recombination theorem and noise in photoconductors

The validity of the well-known generation-recombination (g-ν) theorem is examined for the case of noise in photoconductors. A master equation for the conditional probability of the level occupancies is set up in which the generation and recombination rates are functions of the incident light intensity. A more general g-ν theorem is then derived, in which the light intensity appears explicitly as a driving force. From this theorem the variances and autocorrelation functions of the density perturbations are found, and averaged with respect to the light intensity fluctuations for the case that the incident light beam displays shot noise. The g-ν theorem turns out to be not rigorously valid, correction terms being required due to the fact that the photoconductor is coupled not to the incident light beam intensity but to the number of photons in the crystal volume. These correction terms are small for the case of weak absorption