Magneto-optical study of donor-level crossing in tipped GaAs/(Ga,Al)As quantum wells

We present evidence for an anticrossing between the 2${\mathit{p}}_{+1\mathrm{}}$ and 2${\mathit{p}}_0$ levels of Si donors situated near the center of a GaAs quantum well. This anticrossing, which does not appear for magnetic fields perpendicular to the plane of the sample, is induced by tipping the sample normal away from the direction of the applied magnetic field. All donor transitions were detected with photoconductivity, a method that is standard for GaAs bulk donors but has only recently been employed successfully for donors in quantum wells.