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Direct and simultaneous observation of ultrafast electron and hole dynamics in germanium

Zürch, Michael and Chang, Hung-Tzu and Borja, Lauren J. and Kraus, Peter M. and Cushing, Scott K. and Gandman, Andrey and Kaplan, Christopher J. and Oh, Myoung Hwan and Prell, James S. and Prendergast, David and Pemmaraju, Chaitanya D. and Neumark, Daniel M. and Leone, Stephen R. (2017) Direct and simultaneous observation of ultrafast electron and hole dynamics in germanium. Nature Communications, 8 . Art. No. 15734. ISSN 2041-1723. PMCID PMC5461502. doi:10.1038/ncomms15734.

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Understanding excited carrier dynamics in semiconductors is crucial for the development of photovoltaics and efficient photonic devices. However, overlapping spectral features in optical pump-probe spectroscopy often render assignments of separate electron and hole carrier dynamics ambiguous. Here, ultrafast electron and hole dynamics in germanium nanocrystalline thin films are directly and simultaneously observed by ultrafast transient absorption spectroscopy in the extreme ultraviolet at the germanium M edge. We decompose the spectra into contributions of electronic state blocking and photo-induced band shifts at a carrier density of 8 × 10 cm. Separate electron and hole relaxation times are observed as a function of hot carrier energies. A first-order electron and hole decay of ∼1 ps suggests a Shockley-Read-Hall recombination mechanism. The simultaneous observation of electrons and holes with extreme ultraviolet transient absorption spectroscopy paves the way for investigating few- to sub-femtosecond dynamics of both holes and electrons in complex semiconductor materials and across junctions.

Item Type:Article
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URLURL TypeDescription CentralArticle Paper
Chang, Hung-Tzu0000-0001-7378-8212
Cushing, Scott K.0000-0003-3538-2259
Kaplan, Christopher J.0000-0002-5873-9487
Neumark, Daniel M.0000-0002-3762-9473
Leone, Stephen R.0000-0003-1819-1338
Additional Information:© The Author(s) 2017. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit Received 17 January 2017. Accepted 21 April 2017. Published 01 June 2017. M.Z. acknowledges support by the Army Research Office (ARO) (WN911NF-14-1-0383). H.-T.C. and L.J.B. acknowledge support by the Air Force Office of Scientific Research (AFOSR) (FA9550-15-1-0037). Additional funding for L.J.B. was provided by NSSEFF. Additional funding for C.J.K. was provided by the Defense Advanced Research Projects Agency PULSE program through grant W31P4Q-13-1-0017. J.S.P. and A.G. acknowledge support by NSSEFF. S.K.C. acknowledges a postdoctoral fellowship through the Office of Energy Efficiency and Renewable Energy of the Department of Energy. P.M.K. acknowledges support from the Swiss National Science Foundation (P2EZP2_165252). M.Z. acknowledges support from the Humboldt Foundation. The Department of Energy under contract DE-AC03-76SF00098 is acknowledged for additional experimental equipment. The initial instrument development and experimental work was supported by the Office of Assistant Secretary of Defense for Research and Engineering through a National Security Science and Engineering Faculty Fellowship (NSSEFF) and W.M. Keck Foundation. Theoretical work by C.D.P. and D.P. was performed as part of a User Project at The Molecular Foundry (TMF), Lawrence Berkeley National Laboratory. TMF is supported by the Office of Science, Office of Basic Energy Sciences, of the US Department of Energy, under Contract No. DE-AC02-05CH11231. Portions of C.D.P.’s TDDFT work modelling laser-driven carrier populations were carried out within TIMES at SLAC supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, under Contract No. DE-AC02-76SF00515. Numerical simulations were executed on the Vulcan and Mako computer clusters, administered by the High-Performance Computing Services Group at LBNL. Author Contributions: M.Z. and H.-T.C. conducted the experiments used in this manuscript, established the models and methods and subsequently applied these for evaluating the data. L.J.B. and A.G. conceived the experiment and performed preliminary experiments. C.D.P. and D.P. provided theory support and performed the TDDFT and XAS calculations. M.H.O. performed the sample characterization. D.M.N. and S.R.L. supervised the work. M.Z. wrote the majority of the manuscript with inputs from H.-T.C., P.M.K. and S.C. All authors discussed the results and contributed to the manuscript. Data availability: The experimental data can be obtained on reasonable request from the corresponding authors. The authors declare no competing financial interests.
Funding AgencyGrant Number
Army Research Office (ARO)WN911NF-14-1-0383
Air Force Office of Scientific Research (AFOSR)FA9550-15-1-0037
National Security Science and Engineering Faculty FellowshipUNSPECIFIED
Defense Advanced Research Projects Agency (DARPA)W31P4Q-13-1-0017
Swiss National Science Foundation (SNSF)P2EZP2_165252
Alexander von Humboldt FoundationUNSPECIFIED
Department of Energy (DOE)DE-AC03-76SF00098
W. M. Keck FoundationUNSPECIFIED
Department of Energy (DOE)DE-AC02-05CH11231
Department of Energy (DOE)DE-AC02-76SF00515
PubMed Central ID:PMC5461502
Record Number:CaltechAUTHORS:20180627-103817747
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Official Citation:Zürch, M. et al. Direct and simultaneous observation of ultrafast electron and hole dynamics in germanium. Nat. Commun. 8, 15734 doi: 10.1038/ncomms15734 (2017).
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:87392
Deposited By: George Porter
Deposited On:27 Jun 2018 17:55
Last Modified:15 Nov 2021 20:47

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