Antisite arsenic incorporation in the low temperature MBE of gallium arsenide: Physics and modeling

A stochastic model for simulating the surface growth processes in the low temperature molecular beam epitaxy of gallium arsenide is developed to investigate the incorporation of antisite As and its dependence on the growth conditions including the dynamics of the physisorbed As on the surface. Three different kinetic models with a combination of surface kinetic processes such as incorporation of antisite As, evaporation of antisite As and incorporation of regular As. The kinetic model with all three surface processes was accepted as the best model due to its physical soundness and reasonableness of its model parameters. The arsenic flux, temperature, and growth rate dependences of antisite arsenic (AS(Ga)) obtained from our simulation are in excellent agreement with the experimental results. The activation energy of 1.16 eV and a frequency factor of 4 x 10(12)/s for the evaporation of antisite arsenic obtained from our model are in good agreement with experimental and theoretical estimates. At a constant substrate temperature and growth rate, the antisite arsenic concentration increases with arsenic flux for low fluxes and saturates beyond a critical flux. The critical arsenic flux increases with temperature and the saturation value of the As-Ga concentration decreases with temperature. As the arsenic flux increases, the coverage of the physisorbed layer increases and at a critical flux dictated by the fixed temperature and growth rate, the coverage saturates at its maximum value of unity (a complete monolayer) and hence the concentration of AsG(a) saturates. Lower As-Ga concentration results at higher temperature due to more evaporation of As-Ga. Additionally, an analytical model is developed to predict the As-Ga concentration for various growth conditions.