Quantitative evaluation of germanium displacement induced by arsenic implantation using germanium isotope superlattices

摘要

The displacement of germanium (Ge) atoms induced by arsenic (As) ion implantation at room temperature was investigated using Ge isotope superlattices grown by molecular beam epitaxy. The depth profiles of 74Ge isotopes in the 70GeatGe isotope superlattices before and after ion implantation were obtained by secondary ion mass spectrometry. By representing the experimental data using a conventional integral model, Ge atomic displacement as a function of depth was obtained, from which we determined that 0.75nm is the critical displacement necessary to make the structure appear amorphous under examination by cross-sectional transmission electronmicroscopy. However, we found that the amorphous Ge layers were recrystallized due to a local elevation of temperature caused by the implantation, which indicates that the samples should be cooled down during implantation to avoid the regrowth of amorphous Ge layers for this analysis.