The optical orientation of photoexcited carriers in a highly doped n+-type diode structure with an InGaAs/GaAs quantum well at low temperatures T ≈ 2 K was studied. In magnetic fields corresponding to the disappearance of the upper Landau level, the circular polarization of photoluminescence decreases to an equilibrium value corresponding to the linear polarization of photoexcitation. This is due to the weakening of the random potential screening as the electrons pass through the Fermi level between Landau levels.
S. V. Zaitsev (Sun,) studied this question.