Abstract: Micro-defects and properties of Si-doped,low resistivity GaAs single crystal grown by the vertical gradient freeze (VGF) method are studied and compared with undoped semi-insulating GaAs grown by VGF and liquid encapsulated Czochralski-grown (LEC) methods.Using the A-B etching microscopy method,micro-precipitated defects in the two materials are compared and their formation mechanism is analyzed.Lattice occupation of Si and B atoms and their complex defects are investigated by photoluminescence spectroscopy.Hall measurement results indicate that there is a strong Si self-compensation in the low resistive Si-doped VGF-GaAs single crystal,resulting in a reduction of n-type doping efficiency.As a result,a high initial doping concentration of Si is used in the process of VGF growth of n-type GaAs,and a large amount of impurity precipitate is formed.This situation is enhanced when a high concentration of B in the VGF grown GaAs exists.An approach to reduce defects and increase doping efficiency is discussed.

Key words: VGF, GaAs, micro-defect, single crystal