COUPLING BETWEEN NEAR-SURFACE INXGA1-XAS/GAAS(100) QUANTUM-WELLS AND THE SAMPLE SURFACE

Low temperature PL measurements are reported for a series of In0.26Ga0.74As/GaAs(100) quantum well (QW) samples, with surface-barrier thicknesses ranging from 0 to 500Å GaAs. Each sample consists, in growth order, of 10Å, 30Å and 50Å wells, separated by 1000Å GaAs barriers. The intensity and peak energy of the PL arising from the 50Å well provide a measure of the coupling between this near-surface QW and the sample surface. At the same time, the PL lineshapes obtained from the other two wells allow us to correct any minor variations in growth parameters which might exist within the range of samples studied. The decrease in PL intensity from the near-surface QW only becomes significant for surface-barriers below 100Å in thickness. A 50Å GaAs top barrier results in a PL red-shift of 6 ± 2 meV, whilst a 25Å GaAs surface barrier leads to a much broader PL band, red-shifted by 86 ± 2 meV, with a peak energy corresponding to band edge recombination within the strained In0.26Ga0.74As layer. No luminescence has been observed from the 50Å In0.26Ga0.74As/GaAs surface QW. © 1992.