Electric field dependence of exciton transition energies in GaAs-AlxGa

Abstract

Photocurrent spectroscopy of GaAs-${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$As multiple-quantum-well structures in an electric field perpendicular to the heterointerface is used to study exciton transition energies as a function of electric field up to \ensuremath{\sim}${10}^{5}$ V/cm. A large number of excitonic transitions, as many as 16, are identified. The \ensuremath{\Delta}n\ensuremath{\ne}0 forbidden excitonic transitions grow in intensity with increasing electric field, whereas the \ensuremath{\Delta}n=0 allowed excitonic transitions show the opposite. Both negative and positive shifts of exciton transition energies are observed. The results of these observations are compared with those of a theoretical calculation based on a multiband effective-mass approach which incorporates valence-band mixing effects, and a good agreement is found.