Valley degeneracies in (111) silicon quantum wells

Neerav Kharche, Birck Nanotechnology Center, Network for Computational Nanotechnology, Purdue University
Seongmin Kim, Birck Nanotechnology Center, Network for Computational Nanotechnology, Purdue University
Timothy B. Boykin, Department of Electrical and Computer Engineering, University of Alabama at Huntsville
Gerhard Klimeck, Birck Nanotechnology Center, Network for Computational Nanotechnology, Purdue University

Abstract

(111) silicon quantum wells have been studied extensively, yet no convincing explanation exists for the experimentally observed breaking of sixfold valley degeneracy into two- and fourfold degeneracies. Here, systematic sp(3)d(5)s(*) tight-binding and effective mass calculations are presented to show that a typical miscut modulates the energy levels, which leads to breaking of sixfold valley degeneracy into two lower and four raised valleys. An effective mass based valley-projection model is used to determine the directions of valley minima in tight-binding calculations of large supercells. Tight-binding calculations are in better agreement with experiments compared to effective mass calculations.

Discipline(s)

Nanoscience and Nanotechnology