Existence of metastable step density distributions on GaAs(100) surfaces and their consequence for molecular beam epitaxial growth

Variations in the static and steady-state specular beam intensity (I0 and IS, respectively) in reflection high-energy electron diffraction from GaAs(100) have been examined as a function of substrate temperature (TS) and As4 pressure in molecular beam epitaxy. At a fixed As4 pressure, regimes of reversible and irreversible behavior of I0 and IS as a function of TS are identified. The irreversible regime of I0 is shown to occur at temperatures close to the congruent temperature. At each temperature in this regime, the existence of smoothest, but metastable, surface step density configuration is demonstrated. The maximum in IS is found to occur in this regime. The surface kinetic processes responsible for this behavior are discussed.