Surface Segregation Behavior of B, Ga, Sb, and As Dopant Atoms on Ge(100) and Ge(111) Examined with a First-principles Method

To understand surface segregation behaviour of B, Ga, As, and Sb dopant atoms on Ge (100) and Ge (111) surfaces, the potential energies of these dopant atoms in the five top layers of the surfaces were evaluated by first-principles molecular orbital calculations of model clusters. The obtained potential energy curves of these dopant atoms for Ge (100) closely resemble those for Si (100) surface. On the other hand, Ge (111) surface exhibits different potential profiles as compared with Ge (100) surface. The thermal activation energy between the adsorbed state and sub-surface state was also evaluated for each dopant atom. These energy data determining the driving force and dynamical property of dopant segregation help us to understand the difference in dopant surface segregation phenomena on Ge(100) and Ge(111) surfaces from an atomistic point of view.