Pseudomorphic and Relaxed GeSi:Si Heterostructures Formed by Ion Implantation for Heterepitaxial Templates

摘要

A method of forming GexSi1-x films by thermal oxidation of Ge+- implanted Si is presented. The process involves the segregation of the implanted Ge during oxidation to form a distinct Ge-rich layer at the oxide interface. The composition of the segregated layer can be altered by varying the oxidation conditions as a result of the kinetic competition between oxidation and the interdiffusion of the segregated layer with the underlying Si substrate. Rutherford backscattering results show that the Ge-rich layer becomes more dilute at higher oxidation temperatures. Below a critical thickness, the segregated film forms pseudomorphically on the underlying Si. However, the observed critical thickness greatly exceeds the value predicted (Matthews et. al., 1974) for pseudomorphic growth. Dislocation-free relaxation of the GexSi1-x films formed within a Si-on-insulator (SOI) wafer is achieved with a unique vacancy-injection technique. The encapsulation of the segregated film by the oxide layers in the SOI ensures that the injected vacancies remain within the volume of the film to relax the strain and are not lost to the underlying substrate.