Electric-field effects of the excitons in asymmetric triangular ${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As-GaAs quantum wells

Photocurrent spectroscopy of asymmetric triangular quantum wells in an electric field perpendicular to the heterointerface is used to study exciton transition energy and oscillator strength under electric fields ranging from -${10}^5$ to +${10}^5$ V/cm. The transition energy and oscillator strength strongly depend on the field direction and magnitude. The lowest-lying heavy- and light-hole excitons show linear Stark shifts that are small compared with that of the corresponding rectangular well. A large energy shift is seen for the transition of the n=2 electron subband to m=1 heavy-hole subband in the negative-field region. The results of our experiment are in good agreement with a theoretical calculation based on a multiband effective-mass approach, which incorporates valence-band mixing.