First Principles Calculations of the Adsorption of Arsenic on Ge(001) and Its Surfactant Effect in the Epitaxial Growth of Si on Ge(001)

We have studied the adsorption of As on the (001) surfaces of Ge using first principles total energy calculations. The initial substrate Ge dimers are broken and As forms symmetric dimers on an almost ideally bulk terminated Ge substrate. All the dangling bonds are saturated in this configuration, and the surface is very stable. Arsenic lowers the surface free energy of both Si and Ge surfaces and therefore, it is a good candidate to be used as surfactant in the growth of Si on Ge(001). Our ab initio calculations show that indeed the presence of a terminating As layer modifies the growth mode, promoting epitaxial growth of Si on Ge(001).