Observation of magnetophonon resonance in the miniband transport in semiconductor superlattices

We have studied vertical transport of electrons in GaAs/${\mathrm{Al}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As superlattices by applying high magnetic fields normal to the layers. Strong oscillations of magnetophonon resonance are observed in the temperature range between 150 and 300 K, reflecting the singularity of density of states in the superlattice miniband under quantizing magnetic fields. The miniband-width dependence of the resonant spectra is explained by the formation of forbidden gaps between Landau minibands.