EFFECT OF ION ENERGY ON THE DIFFUSION OF SI IMPLANTED INTO GAAS

The diffusion of Si was studied using secondary ion mass spectroscopy and transmission electron microscopy after implantation into GaAs at e nergies ranging from 20 to 200 keV and at doses ranging from 1 x 10(13 ) to 1 X 10(14) cm-2 followed by furnace annealing. Little or no diffu sion occurred in the higher energy implants (>100 keV) while, in gener al, samples implanted at lower energies (<100 keV) exhibited appreciab le dopant redistribution, regardless of peak implant concentration. Bo th concentration dependent and concentration independent diffusion was observed. Dislocation loop density varied inversely with the amount o f diffusion as a function of implant energy. The Monte Carlo computer program TRIM is able to predict the trends of the implant energy depen dence of the diffusion by considering the excess point defect dose pro duced upon implantation. The influence of this excess defect dose toge ther with surface effects on the diffusion of Si is shown to be consis tent with a vacancy assisted Si diffusion mechanism.