MBE growth kinetics of Si on heavily-doped Si(111):P: a self-surfactant effect

The influence of heavily-doped substrates on the homoepitaxial growth kinetics of Si on Si(111) is studied in real time by means of reflection high-energy electron diffraction as function of temperature and growth rate. The growth experiments were performed by means of molecular beam epitaxy. The obtained results were compared with the growth kinetics on undoped substrates within the framework of nucleation theory. It was found that in comparison with undoped Si(111), the nucleus density in the case of Si(111):P is significantly increased at the same growth conditions that can be attributed to a longer lifetime of the smallest stable islands consisting of a Si pair on the Si(111):P surface. It can be concluded, therefore, that phosphorus is always present on the growing surface during high-temperature preparation of heavily P-doped Si(111). There, the phosphorus atoms saturate dangling bonds at the island edges. For further island growth, phosphorus atoms have to be displayed before silicon adatoms can be incorporated into the island edges, demanding an additional energy. In this sense, phosphorus acts as a surfactant.