MBE-Related Surface Segregation of Dopant Atoms in Silicon

The surface segregation process in Ga and Sb doping during Si molecular beam epitaxy was studied as a function of growth temperature. Above critical temperatures, about 200°C for Ga and 400°C for Sb, almost all dopant atoms were found to float on growing Si surfaces. Below these temperatures, dopants were incorporated in the growing layer and a strong temperature dependence was found in incorporation coefficients of which activation energies were almost the same (∼0.5 eV) for the different dopant atoms. It suggests that there is a mechanism in surface segregation phenomena which is universal and does not depend upon the species of dopant atoms during MBE growth.