The novel behavior of the InAs(001) wetting layer(WL) surfaces grown on GaAs(001)-c(4 x 4)alpha are systematically investigated by our ab initio-based approach and Monte Carlo (MC) simulations under the growth conditions. The ab initio-based approach incorporates the chemical potentials of In atom and As-4 molecule in the gas phase as functions of temperature T and beam equivalent pressure p. The calculated adsorption-desorption boundary curve of In elucidates that In adsorption does not occur on the (2 x 4)alpha 2, (1 x 3), and (2 x 3) WLs but is allowed on the fully relaxed (FR) surface at equilibrium. These results suggest that In adsorption proceeds InAs growth on the initial GaAs(001) and the final InAs(001) FR surfaces, while the novel growth process should be considered on the InAs(001) WL surfaces. The MC simulation results suggest that In adatoms do not reside in the lattice sites on the (1 x 3)/(2 x 3) to quickly desorb from the surfaces under the growth conditions, whereas In adatoms can adsorb and migrate during a certain period on the (2 x 4)alpha 2. On the basis of these results, the novel behavior of InAs(001) WL surfaces is found in In adsorption with As desorption from the (2 x 3) WL surfaces during InAs growth on GaAs(001). (c) 2012 Elsevier B.V. All rights reserved.