Introduction of Uniaxial Strain into Si/Ge Heterostructures by Selective Ion Implantation

A selective-ion-implantation technique was developed for introducing uniaxial strain into Si/Ge heterostructures. Laterally selective ion implantation with a stripe pattern was carried out into a Si substrate, followed by SiGe overgrowth in the whole region. Large strain relaxation of SiGe occurred selectively only in the ion-implanted area. This largely relaxed SiGe was found to considerably affect the strain state of the neighboring strained SiGe in the unimplanted area, resulting in the realization of a highly asymmetric strain state, that is, uniaxial strain. This result indicates that this technique has a high potential to realize high-mobility Si/Ge channels with uniaxial strain.