Competition between magnetic-field- and electric-field-induced localizations in GaAs/Ga0.65Al0.35As superlattices

We have observed that an in-plane magnetic field applied perpendicular to an electric field along the growth axis of GaAs/${\mathrm{Ga}}_{0.65}$ ${\mathrm{Al}}_{0.35}$As superlattices causes the interband Stark transitions seen in photocurrent spectra to lose intensity and eventually to disappear. For sufficiently high magnetic fields, however, new transitions apear, which we interpret as transitions of magnetic origin. A calculation of the interband transitions that includes excitonic effects gives good agreement with the measured energies and intensities and shows that these results are due to a competition between magnetic-field- and electric-field-induced localizations.