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Title: The critical role of substrate disorder in valley splitting in Si quantum wells

Abstract

Atomic-scale disorder at the top interface of a Si quantum well is known to suppress the 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 ~ n 2.7) over the entire experimental range (E v = 30-200 µeV). In conclusion, 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.

Authors:
 [1]; ORCiD logo [1];  [2];  [1];  [1]; ORCiD logo [3];  [4];  [4];  [4];  [1];  [1]; ORCiD logo [1];  [1];  [1]
  1. Univ. of Wisconsin-Madison, Madison, WI (United States)
  2. University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
  3. Delft Univ. of Technology, Delft (The Netherlands)
  4. Intel Corp., Hillsboro, OR (United States)
Publication Date:
Research Org.:
Univ. of Wisconsin-Madison, Madison, WI (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1460093
Alternate Identifier(s):
OSTI ID: 1454355
Grant/Contract Number:  
FG02-03ER46028
Resource Type:
Accepted Manuscript
Journal Name:
Applied Physics Letters
Additional Journal Information:
Journal Volume: 112; Journal Issue: 24; Journal ID: ISSN 0003-6951
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS

Citation Formats

Neyens, Samuel F., Foote, Ryan H., Thorgrimsson, Brandur, Knapp, T. J., McJunkin, Thomas, Vandersypen, L. M. K., Amin, Payam, Thomas, Nicole K., Clarke, James S., Savage, D. E., Lagally, M. G., Friesen, Mark, Coppersmith, S. N., and Eriksson, M. A. The critical role of substrate disorder in valley splitting in Si quantum wells. United States: N. p., 2018. Web. doi:10.1063/1.5033447.
Neyens, Samuel F., Foote, Ryan H., Thorgrimsson, Brandur, Knapp, T. J., McJunkin, Thomas, Vandersypen, L. M. K., Amin, Payam, Thomas, Nicole K., Clarke, James S., Savage, D. E., Lagally, M. G., Friesen, Mark, Coppersmith, S. N., & Eriksson, M. A. The critical role of substrate disorder in valley splitting in Si quantum wells. United States. doi:10.1063/1.5033447.
Neyens, Samuel F., Foote, Ryan H., Thorgrimsson, Brandur, Knapp, T. J., McJunkin, Thomas, Vandersypen, L. M. K., Amin, Payam, Thomas, Nicole K., Clarke, James S., Savage, D. E., Lagally, M. G., Friesen, Mark, Coppersmith, S. N., and Eriksson, M. A. Mon . "The critical role of substrate disorder in valley splitting in Si quantum wells". United States. doi:10.1063/1.5033447. https://www.osti.gov/servlets/purl/1460093.
@article{osti_1460093,
title = {The critical role of substrate disorder in valley splitting in Si quantum wells},
author = {Neyens, Samuel F. and Foote, Ryan H. and Thorgrimsson, Brandur and Knapp, T. J. and McJunkin, Thomas and Vandersypen, L. M. K. and Amin, Payam and Thomas, Nicole K. and Clarke, James S. and Savage, D. E. and Lagally, M. G. and Friesen, Mark and Coppersmith, S. N. and Eriksson, M. A.},
abstractNote = {Atomic-scale disorder at the top interface of a Si quantum well is known to suppress the 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 (Ev ~ n2.7) over the entire experimental range (Ev = 30-200 µeV). In conclusion, 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.},
doi = {10.1063/1.5033447},
journal = {Applied Physics Letters},
number = 24,
volume = 112,
place = {United States},
year = {2018},
month = {6}
}

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Cited by: 2 works
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Figures / Tables:

Figure 1 Figure 1: High-angle annular dark-field images of the three sample heterostructures, taken with a scanning transmission electron microscope (STEM). (a)-(c) Images of the quantum wells and barriers for samples A-C, respectively, taken directly below the accumulation gates of the Hall bars used to perform transport measurements. Brightness corresponds to Gemore » content, with Ge, SiGe, and Si appearing as white, gray, and black, respectively. (d)-(f) High resolution images of the top quantum well barriers in (a)-(c).« less

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    Works referencing / citing this record:

    Spin-Blockade Spectroscopy of Si / Si - Ge Quantum Dots
    journal, July 2019


    Spin-Blockade Spectroscopy of Si / Si - Ge Quantum Dots
    journal, July 2019


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