A sharp potential barrier at the Si/SiGe interface introduces valley splitting (VS), which lifts the 2-fold valley degeneracy in strained SiGe/Si/SiGe quantum wells (QWs). This work examines in detail the effects of Si/SiGe interface disorder on the VS in an atomistic tight binding approach based on statistical sampling. VS is analyzed as a function of electric field, QW thickness, and simulation domain size. Strong electric fields push the electron wavefunctions into the SiGe buffer and introduce significant VS fluctuations from device to device. A Gedankenexperiment with ordered alloys sheds light on the importance of different bonding configurations on VS. We conclude that a single SiGe band offset and effective mass cannot comprehend the complex Si/SiGe interface interactions that dominate VS.
@article{arxiv.1110.4097,
title = {Effects of Interface Disorder on Valley Splitting in SiGe/Si/SiGe Quantum Wells},
author = {Zhengping Jiang and Neerav Kharche and Timothy Boykin and Gerhard Klimeck},
journal= {arXiv preprint arXiv:1110.4097},
year = {2012}
}