Enhanced luminescence of near-surface quantum wells passivated in situ by InP

The authors report optical properties of in situ passivated AlGaAs and GaAs surfaces. The deposition of an ultra thin InP layer (about one monolayer) on the surface of AlGaAs/GaAs structures by metalorganic vapor phase epitaxy (MOVPE) results in drastically reduced surface recombination. The effect is studied by low-temperature photoluminescence (PL) of near-surface AlGaAs/GaAs quantum wells (QW) where the top barrier thickness is varied from 0 to 50 nm. At the thickness of 15 nm the intensity from passivated samples is more than four orders of magnitude larger than obtained from unpassivated structures. Photoreflectance (PR) measurements are used to determine the Fermi level pinning at the surface. The InP passivation is shown to reduce the surface pinning by about 0.3 eV