Vacancy-type defects in boron-reduced VCz GaAs crystals

GaAs crystals have been grown by the vapour pressure controlled Czochralski (VCz) method without boric oxide encapsulant. The melt compositions were in situ controlled and the carbon concentration adjusted. Low doped p- and n-type conducting GaAs has been studied with respect to their content of native and extrinsic defects. The influence of low boron concentrations on vacancy-type defects investigated by positron annihilation technique and cathodoluminescence are presented. The results are discussed in comparison with those obtained on conventionally grown material.