INFLUENCE OF BORON IN SEMIINSULATING GAAS CRYSTALS ON THEIR ELECTRICAL ACTIVATION BY SI-ION IMPLANTATION

The influence of boron on the activation of silicon ions implanted in semi-insulating GaAs crystals grown by liquid encapsulated Czochralski (LEC) method from As-rich melt was investigated using crystals with t he same carbon concentration and the same deep donor (EL2) concentrati on. The resistivity of the crystal was not affected by the boron conce ntration. The sheet resistivity of the implanted layer, however, becam e higher with increase of the boron concentration. An analysis of the electrical properties of the implanted layer suggested that the occupa tion rate of the implanted silicon at As site (Si(As)), Which decides the acceptor level, increased with the boron concentration. The depend ence of this occupation rate was influenced by the annealing temperatu re for activation in the region of low boron concentration under 15 X 10(16) cm-3.