Ions (300keV) of Be were implanted into degenerately Si-doped material to a dose of 1015/cm2. The region near to the projected range remained crystalline, and sub-threshold defects formed at this depth during annealing at 450 to 500C. The defects were identified as being circular prismatic perfect interstitial loops on (110) planes, which originated during the annealing of defect clusters near to 400C. The Burgers vectors of the loops were calculated by comparing experimental and computed defect intensity profiles. The formation of only interstitial loops was attributed to the dislocation bias effect, in which interstitials were attracted more strongly to dislocations than were vacancies. A high density of small loops, with (110) and (111) habit planes, was observed to form slightly above the projected range during annealing at 600C. It extended closer to the surface during annealing at 700C. The density of these loops decreased, and their size increased, during annealing at 800C. They remained small when compared to loops near to the projected range. A shift, slightly deeper into the material, of the loop area per unit volume occurred during annealing at 600C or above (as compared with annealing at 500C). This resulted from the formation of loops as interstitials diffused deeper into the material, while interstitials which diffused to shallower regions were annihilated by the excess vacancy concentrations in this region which developed due to knock-ons during implantation. The decreased size of the loops found here, as compared with those reported previously, was suggested to be the result of the use of degenerately Si-doped, rather than semi-insulating, material.

Transmission Electron Microscopy of Be-Implanted Si-Doped GaAs. R.E.Kroon, J.H.Neethling, J.C.Zolper: Physica Status Solidi A, 2000, 182[2], 607-17