ENHANCED OPTICAL-PROPERTIES OF IN-SITU PASSIVATED NEAR-SURFACE ALXGA1-XAS GAAS QUANTUM-WELLS/

An epitaxial method for in situ passivation of epitaxial AlxGa1-xAs/Ga As surfaces is reported. The deposition of an ultrathin InP layer (abo ut one monolayer) on the surface of AlxGa1-xAs/GaAs structures by meta lorganic vapor phase epitaxy results in drastically reduced surface re combination. The effect is studied by low-temperature photoluminescenc e of near-surface Al0.22Ga0.78As/GaAs quantum wells where the top barr ier thickness is varied from 0 to 50 nm. At the thicknesses of less th an or equal to 5 nm, the intensity from passivated samples is more tha n four orders of magnitude larger than that obtained from unpassivated structures. For a passivated surface quantum well where InP is deposi ted 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 t he luminescence from a quantum well placed at a depth of 50 nm from th e surface. (C) 1996 American Institute of Physics.