期刊
APPLIED PHYSICS LETTERS
卷 112, 期 24, 页码 -出版社
AMER INST PHYSICS
DOI: 10.1063/1.5033447
关键词
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资金
- Army Research Office (ARO) [W911NF-17-1-0274, W911NF-12-1-0607]
- NSF [DMR-1206915]
- Vannevar Bush Faculty Fellowship program - Basic Research Office of the Assistant Secretary of Defense for Research and Engineering
- Office of Naval Research [N00014-15-1-0029]
- DOE [DE-FG02-03ER46028]
- NSF through the UW-Madison MRSEC [DMR-1121288]
Atomic-scale disorder at the top interface of a Si quantum well is known to suppress valley splitting. Such disorder may be inherited from the underlying substrate and relaxed buffer growth, but can also arise at the top quantum well interface due to the random SiGe alloy. Here, we perform activation energy (transport) measurements in the quantum Hall regime to determine the source of the disorder affecting the valley splitting. We consider three Si/SiGe heterostructures with nominally identical substrates but different barriers at the top of the quantum well, including two samples with pure-Ge interfaces. For all three samples, we observe a surprisingly strong and universal dependence of the valley splitting on the electron density (E-v similar to n(2.7)) over the entire experimental range (E-v = 30-200 mu eV). We interpret these results via tight binding theory, arguing that the underlying valley physics is determined mainly by disorder arising from the substrate and relaxed buffer growth. Published by AIP Publishing.
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