Influence of the temperature of implantation on the morphology of defects in MeV implanted GaAs

The authors have studied the influence of the temperature of implantation on the morphology of the defects created during 1-MeV implantation of Si into GaAs, using RBS-channeling and TEM. The annealing behavior of the disorder has also been investigated. Implantation at liquid-nitrogen temperature results in the amorphization of the implanted sample for doses of 2 x 1014 cm-2 and larger. Subsequent rapid thermal annealing at 900 degree C for 10 seconds leads to partial epitaxial regrowth of the amorphous layer. Depending on the implantation dose, the regrowth can proceed from both the front and back ends of the amorphous region or only from the deep end of the implanted zone. Nucleation and growth of a polycrystalline phase occurs concurrently, limiting the extent of the epitaxial regrowth. After implantation at room temperature and above, two distinct types of residual defects are observed or inferred: point defect complexes and dislocation loops. Most of the point defects disappear after rapid thermal annealing at temperatures ≥ 700 degree C. The effect of annealing on the dislocation loops depends on the distance from the surface of the sample. Those in the near surface region disappear upon rapid thermal annealing at 700 degree C, whereas the loops located deeper in the sample grow in size and begin to anneal out only at temperatures in excess of 900 degree C. Implantation at temperatures of 200-300 degree C results in a large reduction in the number of residual point defects. Subsequent annealing at 900 degree C leads to a nearly defect-free surface region and, underneath that, a buried band of partial dislocation loops similar to those observed in the samples implanted at room temperature and subsequently annealed. 8 refs., 5 figs