ANDERSON LOCALIZATION OF THE EXCITON-POLARITON IN DOPED SEMICONDUCTORS

We investigate the localization problem of the exciton-polariton in semiconductors doped with certain neutral impurities. The Hamiltonian of the exciton-polariton scattered by the impurities is derived. The average one- and two-particle Green functions are calculated within the framework of diagrammatic theory. By computing the criteria for the exciton-polariton localization, we show that the localization occurs in a limited frequency range near the exciton resonant frequency. The localization is connected with the scattering resonance of an s wave. Our analysis indicates that in disordered semiconductors where the exciton-polariton effects are important, the localization effects can be easily observed. It is proposed that the absorption edge with an Urbach tail observed in disordered semiconductors should be the result of exciton-polariton localization. © 1990 The American Physical Society.