Preamorphization implantation-assisted boron activation in bulk germanium and germanium-on-insulator

Abstract

The effect of preamorphization implantation (PAI) on boron activation in germanium was studied. It was found that following PAI, significant dynamic annealing occurred during boron implantation in germanium. For small PAI energy which leads to a thin amorphous layer, recrystallization is completed via dynamic annealing during the boron implantation. As a result, a high-temperature postimplant anneal is required to activate the remaining interstitial boron and to annihilate implantation defects. For high PAI energy, while the thick amorphous layer did not recrystallize during the dynamic annealing, it requires a high-temperature anneal in order to completely recrystallize by solid phase epitaxial regrowth (SPER). The optimized PAI energy needs to be tailored such that the surface amorphous layer not only survives dynamic annealing during boron implantation, but also completes the SPER within the designed thermal budget. Full activation of boron can then be achieved without being limited by its solid solubility in germanium. An electrically active boron concentration as high as 4.7×1020∕cm3 was obtained after 400°C rapid thermal annealing. PAI causes a similar effect in GeOI substrates.