INDIUM-INDUCED SMOOTHING OF GAAS FILMS DURING MBE GROWTH

A new technique is reported for obtaining a smooth growth surface duri ng molecular beam epitaxy growth of GaAs on (001) GaAs substrates. The smoothing is achieved by exposing the surface to an indium flux durin g growth of the GaAs buffer layer at high substrate temperature (590 d egrees C). In situ light scattering shows a dramatic reduction in surf ace roughness along the [110] direction during this process, consisten t with ex situ scanning force microscopy measurements on the films, wh ich reveal atomically flat terraces oriented along the <110> direction s. The surface reconstruction shifts from (2 x 4) to (4 x 2) under the indium flux, as revealed by reflection high-energy electron diffracti on. The sticking coefficient of the indium as determined by secondary- ion mass spectroscopy is less than 10%. We attribute the observed effe cts to a transition from group V to group III termination, induced by surface segregation of the nonincorporated indium.