Nonequi librium distribution function of electrons in the forbidden band of a disordered semiconductor under illumination

The mean occupation number of some state in the forbidden band in a disordered semiconductor illuminated by light is found in the one - electron approximation. If the matrix element of the dipolar interaction with the light is less than the level broadening caused by the electron - phonon interaction, the effect of light on the collision processes can be neglected. In this approximation, the small corrections to the Fermi distribution function are found: aconstant, and a term which fluctuates in time with double the frequency of the light. It is shown that the second is smaller than the first if the width of the levels is smaller than the energy of the photon. The expression for the time - independent correct ion can be put in the form of a balance equation havinga clear physical sense.