Subband Structure Engineering in Silicon-on-Insulator FinFETs using Confinement

Splitting between equivalent valleys larger than the spin splitting energy is observed in confined electron systems, e.g. Si films grown either on SiGe substrate or Si dioxide and Si/SiGe quantum dots. Understanding the contribution of different factors in the valley degeneracy lifting is of key importance for the development of spin-based devices in Si. We demonstrate that the splitting between equivalent valleys strongly depends on the confinement direction and that it is orientation dependent. To explain the effect we use a simple but accurate two-band k·p model for the conduction band in silicon. Our data is in good agreement with recent results obtained by first-principle calculations.