On the origin of the uniaxial strain induced in Si/Ge heterostructures with selective ion implantation technique

Abstract

We fabricate uniaxially strained SiGe buffer layers by the selective ion implantation technique, where laterally selective ion implantation with a stripe pattern is performed into a Si substrate, followed by SiGe overgrowth in the whole region. Large strain relaxation of SiGe occurs only in the ion-implanted area. This relaxed SiGe provides shear stress to the neighboring strained SiGe in the unimplanted area, leading to the uniaxial strain relaxation. The observed surface exhibits array of one direction steps which corresponds to misfit dislocations. Relaxation ratios estimated from the dislocation periodicities agree very well with those obtained from x-ray diffraction, indicating that the uniaxial strain is induced by the plastic deformation via dislocation generation. This fact means that the induced uniaxial strain is very stable, and hence, the SiGe layer can be used as a promising template for uniaxially strained Si/Ge channels grown on it.