Millisecond non-melt laser annealing of phosphorus implanted germanium: Influence of nitrogen co-doping

摘要

In this work, we present the results obtained using a CO_2 laser source at 10.6 μm wavelength for the study of the non-melt annealing of phosphorus doped germanium in the millisecond regime. Main objective of this paper is the demonstration of electrically active n~+-p junctions in germanium by implanting phosphorus in p-type substrate while trying to maintain minimal dopant diffusion, which is a critical issue for scaling germanium devices. In addition to the phosphorus diffusion studies, we also explore the presence of nitrogen introduced in the substrate together with phosphorus and we conclude that it can further reduce dopant movement at the expense of lower activation level. The observation is confirmed by both electrical and SIMS measurements. Moreover, density functional theory calculations show that nitrogen-phosphorus co-doping of germanium creates stable N-P complexes that, indeed, are consistent with the deactivation and diffusion suppression of phosphorus.