Valley splitting in strained silicon quantum wells modeled with 2 degrees miscuts, step disorder, and alloy disorder

Neerav Kharche, Birck Nanotechnology Center and Purdue University
Marta Prada, School of Electrical and Computer Engineering, Purdue University
Timothy Boykin, Department of Electrical and Computer Engineering, University of Alabama
Gerhard Klimeck, Purdue University

Abstract

Valley splitting (VS) in strained SiGe/Si/SiGe quantum wells grown on (001) and 2 degrees 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 10(6) atoms, where strain is computed in the valence-force field and electronic structure in the sp(3)d(5)s(*) model.