SURFACE RECONSTRUCTION PHASE-DIAGRAM AND GROWTH ON GAAS(111)B SUBSTRATES BY MOLECULAR-BEAM EPITAXY

A three-dimensional phase diagram is introduced to describe the dependence of GaAs(111)B surface reconstruction phases as observed by reflection high-energy electron diffraction (RHEED) on growth parameters. The 2 x 2, transitional, and square-root 19 x square-root 19 surface reconstructions correspond to different zones in the phase diagram. A simple equation is found to be good approximation in representing the boundaries that separate these zones. From RHEED pattern studies, As coverages are evaluated to be a larger than 0.79 for the 2 x 2 reconstruction and smaller than 0.58 for the square-root 19 x square-root 19 reconstruction. The dependence of surface morphology and crystal quality on growth condition are discussed in terms of RHEED patterns and growth parameters.