Gettering of donor impurities by V in GaAs and the growth of semihyphen;insulating crystals

摘要

Vanadium added to the GaAs melt getters shallow donor impurities (Si and S) and decreases their concentration in the grown crystals. This gettering is driven by chemical reactions in the melt rather than in the solid. Employing V gettering, we were able to grow reproducibly semihyphen;insulating GaAs by horizontal Bridgman and liquidhyphen;encapsulated Czochralski techniques, although V did not introduce any midgap energy levels. The compensation mechanism in these crystals was controlled by the balance between the native midgap donor EL2 and residual shallow acceptors. Vanadium gettering contributed to the reduction of the concentration of shallow donors below the concentration of acceptors. The present findings clarify the longhyphen;standing controversy on the role of V in achieving semihyphen;insulating GaAs.