DIMER FORMATION ON (001) GAAS UNDER ORGANOMETALLIC CHEMICAL VAPOR-DEPOSITION GROWTH-CONDITIONS

We report the first evidence of dimer formation on semiconductor surfaces under atmospheric Pressure (AP) conditions. We successfully employ reflectance-difference spectroscopy to link structures of well-defined (001) GaAs surfaces prepared in ultrahigh vacuum (UHV) by molecular-beam epitaxy with structures of (001) GaAs surfaces prepared in AP by organometallic chemical vapor deposition (OMCVD). These measurements reveal that surface reconstructions also occur under AP-OMCVD conditions, forming structures similar, possibly identical, to the (4 X 2), (2 X 4), c(4 X 4), and disordered c(4 X 4), that occur in UHV. Our results provide a justification for applying the results of UHV studies of these surfaces to non-UHV environments and yield new insights on the mechanisms and kinetics of non-UHV growth.