The effect of stoichiometric disturbance on activation of MeV Si implantation in GaAs

MeV Si implantation into semi-insulating (SI) GaAs is a common technique used to create a deep doping layer. It is observed that the maximum of the carrier concentration is at a shallower depth than that of the implanted atom concentration. This unexpected phenomenon has previously been explained as depth measurement error. Based on our theoretical calculations and experiments, the phenomenon can be attributed to the effect of non-uniform stoichiometric disturbances (NSD) on the activation of implanted atoms. The effect of NSD in GaAs substrate is caused by MeV implantation. After implantation, an excess concentration of the heavier element As exists at shallower depth, while an excess concentration of the lighter element Ga is seen at greater depth. It is likely that Si atoms move more easily to Ga sites when they are heated in an As-rich environment. Excess lattice interstitials build up around the depth of the peak in the implanted Si+ concentration and prevent Si atoms from becoming activated there