Photovoltaic effect in unipolar multivalley semiconductors

Abstract

The theory of the nonequilibrium charge carrier transport in unipolar multivalley semiconductors is developed. It is shown that the diffusion of photoexcited nonequilibrium heavy and light electrons in multivalley semiconductors is a correlated process, like the ambipolar diffusion in the case of the electron-hole plasma. The light-induced intervalley transitions, resulting in the imbalance between the subsystems of the light and heavy electrons, give rise to the electromotive force (emf) through the mechanism of the Dember photovoltaic effect. The value of the emf occurring in the ‘metal-semiconductor-metal’ structure is calculated in the linear approximation in terms of the light intensity as a small parameter. It is shown that the emf is determined by the conductivity of heavy and light electron subsystems, as well as by the surface conductivity of the metal-semiconductor interface.