Valley splitting !VS" in strained SiGe/Si/SiGe quantum wells grown on !001" and 2° miscut substrates is computed in a magnetic field. Calculations of flat structures significantly overestimate, while calculations of perfectly ordered structures underestimate experimentally observed VS. Step disorder and confinement alloy disorder raise the VS to the experimentally observed levels. Atomistic alloy disorder is identified as the critical physics, which cannot be modeled with analytical effective mass theory. NEMO-3D is used to simulate up to 106 atoms, where strain is computed in the valence-force field and electronic structure in the sp3d5s* model.
Date of this Version