Magnetoluminescence oscillations of a doped (Al,Ga)As/GaAs single heterojunction

We have studied the photoluminescence spectra of a modulation doped (Al,Ga)As/GaAs single heterojunction in magnetic fields to 50 T at 4 K. When an external excitation is introduced to the system, photocreated electrons push the Fermi energy close to the second subband and lead to the formation of a hybridized eigenstate of the second subband (E1) exciton and the first subband (E0) two-dimensional electron state. The conduction-band hybridization enhances nonlinear behavior of magnetoexciton transitions in the optical process. At low fields, the E1 magnetoexciton transition is dominant,because the E1 hole wave-function overlap is larger than that of E0 hole. Beyond the v=2 quantum Hall state, where electron screening becomes negligible, electron-hole attraction is dominant, and holes tend to move to the interface. As a consequence, the photoluminescence oscillator strength switches from the magneto-exciton transition to the lowest-Landau-level subband transition above 13 T. [S0163-1829(98)03240-8].