Study of silicon-doped VGF-GaAs by DSL-etching and LVM spectroscopy and the influence of B2O3 coating

Silicon-doped GaAs crystals with free carrier concentrations between 2×1017 and 3×1018 cm−3 were grown successfully with and without B2O3-coating using the Vertical Gradient Freeze method. Growth experiments with full encapsulation (FE-VGF) of the GaAs resulted in etch pit densities lower than 200 cm−2 with an X-shaped configuration in all investigated crystal wafers. The application of B2O3 causes a reduction in dislocation density and a decrease in carrier concentration combined with the incorporation of boron. Local vibrational mode (LVM) spectroscopy was used to study the incorporation of silicon and boron in different as-grown samples compensated by electron irradiation. In addition to the LVM lines of Si related defects, the modes of BGa, BAs and SiGa–BAs were observed in crystals grown with full encapsulation. The incorporation of B in equal quantities besides Si dopant seems to be responsible for the dislocation reduction.