Evolution of energy levels of a GaAs/AlGaAs superlattice under the influence of a strong magnetic field

We present photocurrent spectra of the Wannier–Stark ladder of a GaAs/AlGaAs superlattice in a magnetic field up to 9 T and oriented along the growth direction of the superlattice. The Landau and Wannier–Stark quantization directions are perpendicular to each other. The salient observation is the evolution of Landau fans for the different Wannier–Stark transitions, with the Landau fan assigned to the spatially direct Wannier–Stark-ladder transitions being very pronounced quite in contrast to the Landau fans for the spatially indirect Wannier–Stark transitions which are weak.