A Monte Carlo simulation study on the structural change of the GaAs(001) surface during MBE growth

A newly developed Monte Carlo (MC) simulation based on the electron counting model called electron counting Monte Carlo (ECMC) simulation, is used to investigate the structural change of the As-stabilized GaAs(001) surface during MBE growth. The calculated results imply that the GaAs(001) surface changes its structure from initial(2 x 4)beta 2 to (2 x 4)alpha with an increase in Ga adatoms and show that subsequent As adsorption produces the (2 x 4)beta 1 structure. Ga adatoms on the GaAs(001)-(2 x 4)beta 1 structure occupy ?he lattice sites on the As-dimers at the low Ga adatom coverage of theta(Ga) less than or equal to 2/16. As the coverage increases in the range of theta(GA) greater than or equal to 3/16, Ga adatoms tend to reside in the lattice sites in the missing dimer region. These results are qualitatively consistent with those obtained by ab initio calculations. Further As incorporation onto the missing dimer row is also simulated by considering the dependence of As adsorption energy on Ga adatom coverage.