Self-organization of GeAs nanodots in relaxed Si0.5Ge0.5 alloys

We report on the bimodal distribution and long-range ordering of GeAs nanod ots obtained in strain-relaxed epitaxial Si0.5Ge0.5 alloy layers after arse nic implantation and rapid thermal annealing. GeAs dots of two different av erage sizes around 15 and 55 nm are found after high temperature rapid ther mal annealing. The larger dots are of elliptical shape and located at the s urface region; they are distributed preferably along < 110 > directions whi ch correlates well with the observed cross-hatch pattern. The origin of the bimodal precipitate distribution as well as of the long-range ordering eff ect of the GeAs nanodots is discussed in terms of strain-induced nucleation and diffusion-limited growth. (C) 2001 American Institute of Physics.