2-DIMENSIONAL ELECTRON-GAS IN DOUBLE-QUANTUM WELLS WITH TILTED BANDS

When a voltage is applied to double quantum wells based on AlGaAs/GaAs heterostructures with contact regions (n-i-n structures), a two-dimen sional (2D) electron gas appears in one of the quantum wells. Under il lumination which generates electron-hole pairs, the photoexcited holes become localized in a neighboring quantum well and recombine radiativ ely with the 2D electrons (tunneling recombination through the barrier ). The appearance, ground-state energy, and density of the degenerate 2D electron gas are determined from the structure of the Landau levels in the luminescence and luminescence excitation spectra as well as fr om the oscillations of the radiative recombination intensity in a magn etic field with detection directly at the Fermi level. The electron de nsity is regulated by the voltage between the contact regions and incr eases with the slope of the bands. For a fixed slope of the bands the 2D-electron density has an upper limit determined by the resonance tun neling of electrons into a neighboring quantum well and subsequent dir ect recombination with photoexcited holes. (C) 1997 American Institute of Physics.