The balance equation for the electron density is derived in the case of predominant Auger recombination in a semiconductor whose electron energy spectrum is described well by the Kane model. The degree of degeneracy of the electron gas is not restricted. The temperature and carrier-density dependences of the differential carrier lifetime are analyzed for an arbitrary rate of optical excitation of free carriers. When the threshold value of the overlap integral between the electron and heavy-hole wave function vanishes, there is a change in the temperature dependence (and in the case of a degenerate electron gas also a change in the carrier-density dependence) of the Auger recombination time compared with the case when the energy band structure has no point of degeneracy. An equation describing the carrier density relaxation is obtained.