SCANNING-TUNNELING-MICROSCOPY STUDY OF GAAS STEP STRUCTURES ON VICINAL SUBSTRATE GROWN BY METALORGANIC CHEMICAL-VAPOR-DEPOSITION

Scanning tunneling microscopy (STM) is used to study the step structure of metalorganic chemical vapor deposition (MOCVD)-grown GaAs on a vicinal substrate. We passivated the as-grown surfaces with As in a vacuum chamber connected to the MOCVD system in order to protect it from oxidation during its transfer to the STM system. The undulation amplitude of the monolayer steps grown on a surface misoriented in the [110] direction is about twice that of these grown on a surface misoriented in the [($) over bar 110] direction. On a substrate at misorientation angles equal to or less than 7.0 degrees, surfaces show a monolayer step staircase when the growth temperature (T-g) >650 degrees C; step bunching occurs and the vicinal surface decomposed into (001) terraces and facets on which steps bunch when 575 degrees C less than or equal to T-g less than or equal to 650 degrees C; and elliptical two-dimensional islands form between the monolayer steps because of a decrease of Ga diffusion coefficient when T-g<575 degrees C.