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 x 10(17) and 3 x 10(18) 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 B-Ga, B-As and Si-Ga-B-As 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. (C) 1999 Elsevier Science S.A. All rights reserved.