Structural studies of GaAs implanted with N or coimplanted with other eleme
nts showed that, in addition to typical postimplant defects, small voids we
re present in the implanted region in such materials. Comparison of the mic
rostructure found in these layers with electrical results indicates that th
ese voids are responsible for the low activation efficiency of N implanted
into GaAs. The results show that the N-induced enhancement of the donor act
ivation efficiency can be achieved only in a void-free region of the implan
ted sample. (C) 2001 American Institute of Physics.