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Imaging the Thermalization of Hot Carriers after Thermionic Emission over a Polytype Barrier

Könemann, Fabian ; Chen, I. Ju LU ; Lehmann, Sebastian LU ; Thelander, Claes LU and Gotsmann, Bernd (2020) In Physical Review Applied 13(5).
Abstract

The thermalization of nonequilibrium charge carriers is at the heart of thermoelectric energy conversion. In nanoscale systems, the equilibration length can be on the order of the system size, leading to a situation where thermoelectric effects need to be considered as spatially distributed, rather than localized at junctions. The energy exchange between charge carriers and phonons is of fundamental scientific and technological interest, but their assessment poses significant experimental challenges. We address these challenges by imaging the temperature change induced by Peltier effects in crystal phase engineered InAs nanowire (NW) devices. Using high-resolution scanning thermal microscopy (SThM), we study current-carrying InAs NWs,... (More)

The thermalization of nonequilibrium charge carriers is at the heart of thermoelectric energy conversion. In nanoscale systems, the equilibration length can be on the order of the system size, leading to a situation where thermoelectric effects need to be considered as spatially distributed, rather than localized at junctions. The energy exchange between charge carriers and phonons is of fundamental scientific and technological interest, but their assessment poses significant experimental challenges. We address these challenges by imaging the temperature change induced by Peltier effects in crystal phase engineered InAs nanowire (NW) devices. Using high-resolution scanning thermal microscopy (SThM), we study current-carrying InAs NWs, which feature a barrier segment of wurtzite (WZ) of varying length in a NW of otherwise zincblende (ZB) crystal phase. The energy barrier acts as a filter for electron transport around the Fermi energy, giving rise to a thermoelectric effect. We find that thermalization through electron-phonon heat exchange extends over the entire device. We analyze the temperature profile along a nanowire by comparing it to spatially dependent heat diffusion and electron thermalization models. We are able to extract the governing properties of the system, including the electron thermalization length of 223±9nm, Peltier coefficient and Seebeck coefficient introduced by the barrier of 39±7mV and 89±21μV/K, respectively, and a thermal conductivity along the wire axis of 8.9±0.5 W/m K. Finally, we compare two ways to extract the elusive thermal boundary conductance between the NW and underlying substrate.

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author
; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Physical Review Applied
volume
13
issue
5
article number
054035
publisher
American Physical Society
external identifiers
  • scopus:85085843169
ISSN
2331-7019
DOI
10.1103/PhysRevApplied.13.054035
language
English
LU publication?
yes
id
20019be2-9edd-4334-933b-5bc015c2e841
date added to LUP
2020-12-30 13:02:46
date last changed
2023-11-20 18:48:30
@article{20019be2-9edd-4334-933b-5bc015c2e841,
  abstract     = {{<p>The thermalization of nonequilibrium charge carriers is at the heart of thermoelectric energy conversion. In nanoscale systems, the equilibration length can be on the order of the system size, leading to a situation where thermoelectric effects need to be considered as spatially distributed, rather than localized at junctions. The energy exchange between charge carriers and phonons is of fundamental scientific and technological interest, but their assessment poses significant experimental challenges. We address these challenges by imaging the temperature change induced by Peltier effects in crystal phase engineered InAs nanowire (NW) devices. Using high-resolution scanning thermal microscopy (SThM), we study current-carrying InAs NWs, which feature a barrier segment of wurtzite (WZ) of varying length in a NW of otherwise zincblende (ZB) crystal phase. The energy barrier acts as a filter for electron transport around the Fermi energy, giving rise to a thermoelectric effect. We find that thermalization through electron-phonon heat exchange extends over the entire device. We analyze the temperature profile along a nanowire by comparing it to spatially dependent heat diffusion and electron thermalization models. We are able to extract the governing properties of the system, including the electron thermalization length of 223±9nm, Peltier coefficient and Seebeck coefficient introduced by the barrier of 39±7mV and 89±21μV/K, respectively, and a thermal conductivity along the wire axis of 8.9±0.5 W/m K. Finally, we compare two ways to extract the elusive thermal boundary conductance between the NW and underlying substrate.</p>}},
  author       = {{Könemann, Fabian and Chen, I. Ju and Lehmann, Sebastian and Thelander, Claes and Gotsmann, Bernd}},
  issn         = {{2331-7019}},
  language     = {{eng}},
  number       = {{5}},
  publisher    = {{American Physical Society}},
  series       = {{Physical Review Applied}},
  title        = {{Imaging the Thermalization of Hot Carriers after Thermionic Emission over a Polytype Barrier}},
  url          = {{http://dx.doi.org/10.1103/PhysRevApplied.13.054035}},
  doi          = {{10.1103/PhysRevApplied.13.054035}},
  volume       = {{13}},
  year         = {{2020}},
}