Scanning Tunneling Microscopy Study of GaAs Step Structures on Vicinal Substrate Grown by Metalorganic Chemical Vapor Deposition

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Abstract
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 [1̄10] direction. On a substrate at misorientation angles equal to or less than 7.0°, surfaces show a monolayer step staircase when the growth temperature (T g)>650° C; step bunching occurs and the vicinal surface decomposed into (001) terraces and facets on which steps bunch when 575° C≤T g≤650° C; and elliptical two-dimensional islands form between the monolayer steps because of a decrease of Ga diffusion coefficient when T g<575° C.