Reduction of SiGe heterointerface mixing by atomic hydrogen irradiation during molecular beam epitaxy and its mechanism

Ge surface segregation is a phenomenon in which Ge segregates to the epitaxial surface during MBE growth, and atomic hydrogen irradiation during MBE growth can reduce this phenomenon. To reveal the mechanism of both the phenomenon and the hydrogen irradiation effect, we have investigated the dependence of the phenomenon, with and without atomic hydrogen irradiation, on the Si growth rate, the substrate orientation, and the substrate temperature. The segregated Ge concentration does not depend exponentially on the Si growth thickness and a second-order reaction as well as a first-order reaction is necessary to describe the Ge segregation phenomenon in Si. The segregation length on Si(1 0 0) is larger than that on Si(1 1 1). This difference in segregation lengths appears to be due to a difference in the number of segregation paths in different substrates. Atomic hydrogen irradiation does not change the potential of the two-energy-state model, but it does change the probability of the second-order reaction occurring. As a result, the segregation is reduced.