Si CMOS compatible, compliant integration of lattice-mismatched semiconductors on Si(001): Example of fully coherent Ge/Si nanostructures

In this paper, we revisited the so-called "compliance" heteroepitaxy concept which was e.g. reported by Hirth and Lothe already in the early sixties. The vision of this concept is to shift the critical thickness for plastic relaxation by defect injection of a growing heteroepitaxial thin film structure on a substrate to infinity. In other words, in case of the Ge/Si heterosystem, defect free Ge heterostructures on Si(001) without threading arm defects in the volume of the Ge film and without misfit dislocations at the Ge/Si heterostructure interface would result. To achieve this goal, the compliance approach is based on a subtle strain partitioning between Ge film and Si substrate so that the increasing mismatch strain is not only absorbed in the epitaxial Ge film but also in part into the Si substrate. As Hirth and Lothe proposed the use of nanometer thick and thus unrealistically thin Si substrates, it was our goal to establish compliant growth for the Ge/Si heterosystem under Si CMOS compatible conditions.