The effect of coimplantation on the electrical activity of implanted carbon in GaAs

The effects of radiation damage and stoichiometry on the electrical activity of carbon implanted in GaAs are studied. Damage due to implantation of an ion heavier than C increases the number of C atoms which substitute for As (C_As). Creation of an amorphous layer by implantation and the subsequent solid phase epitaxy during annealing further enhances the concentration of C_As. However, the free carrier concentration does not increase linearly with increasing concentration of C_As due to compensating defects. Activation of implanted C is maximized by maintaining the stoichiometry of the substrate which reduces the number of compensating defects in the crystal. Under optimum conditions for carbon implanted at a dose of 5×10¹⁴ cm^-2, the carbon acceptor activity can be increased from 2% to 65% of the total implanted carbon.