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Growth physics of silicon-based heterostructures in MBE processes

Si-based heteroepitaxy is almost synonymous with strained layer epitaxy. The strain in a planar heteroepitaxial system is biaxial in the plane of the sample surface, and uniaxial in the direction perpendicular to the sample surface. It is to be differentiated from hydrostatic strain which has equal values in all directions. Strain plays a key role in device applications of the GeSi/Si heterostructures. However, it also imposes serious limitations on them. An almost universal constraint is the critical layer thickness for strain relaxation through dislocation introduction. Another potential problem, with strain is relaxation through 3D growth. For a given device application, whether the need is to relax or to utilize strain in the GeSi/Si heterostructure, control of MBE growth parameters is necessary to achieve the goal. The purpose of this review is to provide information of some key issues on how the device- important properties of the MBE grown silicon-based heterostructures can be controlled by the growth conditions. The considerations are based on the current understanding of the MBE growth physics of this material system.