Some Insights into the Relaxation Mechanisms of Germanium Growing on (001) Si by Ultrahigh Vacuum Chemical Vapor Deposition

Abstract

Recent developments in the control by UHVCVD of relaxation mechanisms are reported and discussed. Considering the elastic domain, it is shown that the nucleation of Ge QDs can be accurately driven in order to form isolated single dots or regular arrays of dots, as a consequence of an additional relaxation effect at Si mesas edges. The plastic relaxation can be drastically favored at low deposition temperature : it was found to proceed during the deposition of the first two monolayers at 330ºC. The morphology of the corresponding Ge films becomes stable above a critical thickness value lying just below 27 nm. A further re-growth at 600ºC leads to a low disorder level and a low roughness, while the misfit dislocations are located at the very Ge-Si interface. At last, the growth of Ge on oxidized Si is shown as a promising alternative for growing Ge films free of misfit dislocations.