The results of theoretical and experimental investigation of nonlinear effects revealed in solid semiconductor solutions under optical orientation of charge carriers are presented. Those effects caused by hyperfine interaction between the carriers and the crystal lattice nuclei manifest themselves in the appearance of bistability and auto-oscillations of luminescence polarization excited by circularly polarized light. Theoretical analysis of data obtained in the experiments carried out in a strong magnetic field (B approximately 100-1000 G) allowed the authors to determine the values of phenomenological parameters describing the Overhauser effective nucleus field.