Structural studies of samples implanted with N, or co-implanted with other elements, showed that - in addition to typical post-implantation defects - small voids were present in the implanted regions of such materials. A comparison of the microstructures found, with electrical results, indicated that these voids were responsible for the low activation efficiency of N which was implanted into GaAs. The results showed that N-induced enhancement of the donor activation efficiency could be achieved only in a void-free region of the implanted sample.

Influence of Microstructure on Electrical Properties of Diluted GaNxAs1–x formed by Nitrogen Implantation. J.Jasinski, K.M.Yu, W.Walukiewicz, J.Washburn, Z.Liliental-Weber: Applied Physics Letters, 2001, 79[7], 931-3