Electric field dependence of exciton oscillator strengths in GaAs-AlxGa1−xAs quantum wells studied by photocurrent spectroscopy

Abstract

Photocurrent spectroscopy of GaAs-${\mathrm{Al}}_{\mathrm{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As multiple-quantum-well structures with an electric field applied perpendicular to the heterointerface is used to study exciton oscillator strengths as a function of electric field up to ∼${10}^5$ V/cm. The electric field dependence of exciton oscillator strengths is attributed to a complicated interaction between local variation of zone-center electron- and hole-wave-function overlap and strong valence-band mixing. The results of experiment are compared with a theoretical calculation based on a multiband effective-mass approach which incorporates valence-band mixing effects, and in which good agreement is found. Strong mixing between the 2s and 2p states of the n=1 light-hole exciton and the 1s state of the n=2 heavy-hole to n=1 electron exciton is identified.