Magnetic field dependence of valley-splitting in miscut (100) SiGe/Si/SiGe quantum wells

1. Objective Explain experimentally observed suppression in valley-splitting in miscut (100) Si QWs Study effect of alloy disorder and step roughness at Si/SiGe interface on the electronic structure Approach Model miscut Si QWs along with SiGe buffers to include strain and atomistic alloy disorder in SiGe buffer Strain relaxation: VFF-Keating Magnetic field: Peierl’s substitution Step roughness: replicate experimentally observed surface morphology on the atomistic grid Ref: Appl. Phys. Lett. 90, 092109 (2007) Impact Alloy disorder in SiGe and step roughness at Si/SiGe interface is crucial to accurately model valley-splitting Model predicts experimentally observed valley-splitting without any ad-hoc fitting parameters Expt Alloy disorder SiGe Alloy disorder Ideal Si Expt No SiGe buffer Rough steps Alloy+Step disorder 15 nm Expt Ideal SiGe Step disorder Si SiGe Ideal Magnetic field dependence of valley-splitting in miscut (100) SiGe/Si/SiGe quantum wells Strain – 10 million atoms 10 nm 16 nm Elect. – 2 million atoms 150 nm