A study on carbon incorporation in semi-insulating GaAs crystals grown by the vapor pressure controlled Czochralski technique (VCz) part I: Experiments and results

In the past it has been demonstrated that the carbon concentration of large semi-insulating (SI) GaAs single crystals grown by the conventional liquid encapsulation Czochralski (LEC) technique can be controlled by several met hods including variations of growth parameters. It was the aim of the prese nt paper to clarify which of the relationships of LEC growth could be used for a carbon control in the VCz-method characterized by the application of an inner chamber made from graphite to avoid selective As evaporation. In d etail this comprised a study of the influence of several growth parameters like the water content of the boric oxide, the composition of the working a tmosphere, the gas flow, a titanium gettering and additions of gallium oxid e. As a result, for the first time carbon concentrations down to approximat e to 10(14) cm(-3) were obtained in 3" (75 mm) diameter VCz crystals.