We investigated the dependence of Arsenic antisite defect concentration and that of epitaxial thickness (t_epi), above which a transition to three dimensional growth appears, on the growth conditions of LTGaAs layers grown by MBE. The antisite defect concentration and the lattice expansion of LT layers grown at 180°C–250°C initially increases with increasing pressure ratio P_As4/P_Ga and then saturates. On the other hand, t_epi decreases with increasing P_As4/P_Ga and depends strongly on the presence of roughness on the substrate surface. Our results indicates that the transition to 3D growth in LT layers is caused by the reduced surface mobility of the atoms impinging on the growth front during the epitaxy. We also determined the optimum LT growth conditions in order to achieve both maximum As_Ga concentration (∼1.4×10²⁰ cm⁻³) and a smooth surface without a transition to 3D growth.

Source: Microelectronic Engineering

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