THEORETICAL-STUDY OF ANTISITE ARSENIC INCORPORATION IN THE LOW-TEMPERATURE MOLECULAR-BEAM EPITAXY OF GALLIUM-ARSENIDE

A stochastic model for simulating the surface growth processes in the low temperature molecular beam epitaxy of gallium arsenide is develope d, including the presence and dynamics of a weakly bound physisorbed s tate for arsenic. The physisorbed arsenic is allowed to incorporate in to the arsenic site or gallium site (antisite) and evaporate. Addition ally, the antisite As is allowed to evaporate from the surface of the crystal. The arsenic flux, temperature and growth rate dependences of antisite arsenic (As-Ga) concentration and the resultant % lattice mis match obtained from our simulation are in excellent agreement with the experimental results. The activation energy of 1.16 eV for the evapor ation of antisite arsenic from the crystal obtained from our model is in good agreement with theoretical estimates. At a constant substrate temperature and growth rate (Ga flux rate), the antisite arsenic conce ntration and hence, the % lattice mismatch increase with arsenic flux in the low flux regime and saturate for high flux regime. The critical arsenic flux at which the AsGa concentration and the % lattice mismat ch saturate, increases with temperature. The AsGa concentration and % lattice mismatch saturate at lower values for higher temperatures. As the arsenic flux increases, the coverage of the physisorbed layer incr eases and at a critical flux dictated by the fixed temperature and gro wth rate, the coverage saturates at its maximum value of unity (a comp lete monolayer) and hence, the concentration of Asc, and % lattice mis match saturate. Lower Asc, concentration and % lattice mismatch result at higher temperature due to more evaporation of AsGa from the surfac e of the growing crystal. Additionally, an analytical model is develop ed to predict the AsGa concentration and % lattice mismatch for variou s growth conditions. (C) 1998 American Institute of Physics. [S0021-89 79(98)00711-7].