PHOTOLUMINESCENCE EXCITATION SPECTROSCOPY OF WIDE PARABOLIC GAAS/ALGAAS QUANTUM-WELLS

We have measured photoluminescence excitation (PLE) spectra of remotely doped wide (>4000 Å) parabolic GaAs AlxGa1-xAs quantum wells of several curvatures and electron densities. The PLE spectra for an empty parabolic well (4640 Å wide) show peaks at energies consistent with the calculated interband transition energies for the parabolic conduction and valence band potentials, using QCB=0.65±0.10 as the fraction of the band offset in the conduction band. For two parabolic wells with the same growth parameters as the empty well, but partially filled with electrons by remote doping, the lower energy peaks are modified, while at higher energy the spectra are dominated by a series of peaks with uniform spacing, which are not observed in the empty parabolic well spectra or that of remotely doped square wells with similar electron sheet densities. Similar PLE spectra are obtained for a wider (5680 Å) remotely doped parabolic well. The uniform peak spacings are approximately equal to the simple harmonic oscillator energy spacings of the corresponding bare parabolic conduction band edge curvatures. © 1991.