Suppressed electronic contribution in thermal conductivity of Ge2Sb2Se4Te

Kiumars Aryana; Yifei Zhang; John A Tomko; Md Shafkat Bin Hoque; Eric R Hoglund; David H Olson; Joyeeta Nag; John C Read; Carlos Ríos; Juejun Hu; Patrick E Hopkins

doi:10.1038/s41467-021-27121-x

Suppressed electronic contribution in thermal conductivity of Ge₂Sb₂Se₄Te

Nat Commun. 2021 Dec 10;12(1):7187. doi: 10.1038/s41467-021-27121-x.

Authors

Kiumars Aryana¹, Yifei Zhang², John A Tomko¹, Md Shafkat Bin Hoque¹, Eric R Hoglund³, David H Olson¹, Joyeeta Nag⁴, John C Read⁴, Carlos Ríos^{5

6}, Juejun Hu², Patrick E Hopkins^{7

8

9}

Affiliations

¹ Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, VA, 22904, USA.
² Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.
³ Department of Materials Science and Engineering, University of Virginia, Charlottesville, VA, 22904, USA.
⁴ Western Digital Corporation, San Jose, CA, 95119, USA.
⁵ Department of Materials Science and Engineering, University of Maryland, College Park, MD, 20742, USA.
⁶ Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD, 20742, USA.
⁷ Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, VA, 22904, USA. phopkins@virginia.edu.
⁸ Department of Materials Science and Engineering, University of Virginia, Charlottesville, VA, 22904, USA. phopkins@virginia.edu.
⁹ Department of Physics, University of Virginia, Charlottesville, VA, 22904, USA. phopkins@virginia.edu.

Abstract

Integrated nanophotonics is an emerging research direction that has attracted great interests for technologies ranging from classical to quantum computing. One of the key-components in the development of nanophotonic circuits is the phase-change unit that undergoes a solid-state phase transformation upon thermal excitation. The quaternary alloy, Ge₂Sb₂Se₄Te, is one of the most promising material candidates for application in photonic circuits due to its broadband transparency and large optical contrast in the infrared spectrum. Here, we investigate the thermal properties of Ge₂Sb₂Se₄Te and show that upon substituting tellurium with selenium, the thermal transport transitions from an electron dominated to a phonon dominated regime. By implementing an ultrafast mid-infrared pump-probe spectroscopy technique that allows for direct monitoring of electronic and vibrational energy carrier lifetimes in these materials, we find that this reduction in thermal conductivity is a result of a drastic change in electronic lifetimes of Ge₂Sb₂Se₄Te, leading to a transition from an electron-dominated to a phonon-dominated thermal transport mechanism upon selenium substitution. In addition to thermal conductivity measurements, we provide an extensive study on the thermophysical properties of Ge₂Sb₂Se₄Te thin films such as thermal boundary conductance, specific heat, and sound speed from room temperature to 400 °C across varying thicknesses.

Abstract

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