Te-defect interaction in GaSb: donor-vacancy pair or DX-center?

We have studied Te-119 donor atoms in GaSb incorporated by a recoil implant ation technique by applying emission Mossbauer spectroscopy on Sn-119. Sinc e Te-119 decays via the intermediate Sb-119 the thermal stability of the mi croscopic environment of the implanted Te atoms can be probed either in the Te state or, after transmutation, in the Sb state. It is found that part o f the probes is situated in a strongly distorted configuration which cannot be annealed as long as the probes are Te. After transmutation to Sb the di storted state anneals at 405 K. From these results we conclude that the dis torted configuration is implantation induced (very likely a probe-vacancy a ssociation) stabilized by the Te chemistry and not a DX center which should anneal with a much lower barrier.