An epitaxial method for in situ passivation of epitaxial AlxGa1−xAs/GaAs surfaces is reported. The deposition of an ultrathin InP layer (about one monolayer) on the surface of AlxGa1−xAs/GaAs structures by metalorganic vapor phase epitaxy results in drastically reduced surface recombination. The effect is studied by low-temperature photoluminescence of near-surface Al0.22Ga0.78As/GaAs quantum wells where the top barrier thickness is varied from 0 to 50 nm. At the thicknesses of ≤5 nm, the intensity from passivated samples is more than four orders of magnitude larger than that obtained from unpassivated structures. For a passivated surface quantum well where InP is deposited directly onto the GaAs quantum well, we observe a blueshift of 15 meV and an intensity reduction of only a factor of 10 as compared to the luminescence from a quantum well placed at a depth of 50 nm from the surface.
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Lipsanen et al. (1996) studied this question.