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Structure and Composition of Isolated Core-Shell (In,Ga) N/GaN Rods Based on Nanofocus X-Ray Diffraction and Scanning Transmission Electron Microscopy

Krause, Thilo ; Hanke, Michael ; Nicolai, Lars ; Cheng, Zongzhe ; Niehle, Michael ; Trampert, Achim ; Kahnt, Maik LU orcid ; Falkenberg, Gerald ; Schroer, Christian G. and Hartmann, Jana , et al. (2017) In Physical Review Applied 7(2).
Abstract

Nanofocus x-ray diffraction is used to investigate the structure and local strain field of an isolated (In,Ga)N/GaN core-shell microrod. Because the high spatial resolution of the x-ray beam is only 80×90 nm2, we are able to investigate several distinct volumes on one individual side facet. Here, we find a drastic increase in thickness of the outer GaN shell along the rod height. Additionally, we performed high-angle annular dark-field scanning-transmission-electron-microscopy measurements on several rods from the same sample showing that (In,Ga)N double-quantum-well and GaN barrier thicknesses also increase strongly along the height. Moreover, plastic relaxation is observed in the top part of the rod. Based on the experimentally... (More)

Nanofocus x-ray diffraction is used to investigate the structure and local strain field of an isolated (In,Ga)N/GaN core-shell microrod. Because the high spatial resolution of the x-ray beam is only 80×90 nm2, we are able to investigate several distinct volumes on one individual side facet. Here, we find a drastic increase in thickness of the outer GaN shell along the rod height. Additionally, we performed high-angle annular dark-field scanning-transmission-electron-microscopy measurements on several rods from the same sample showing that (In,Ga)N double-quantum-well and GaN barrier thicknesses also increase strongly along the height. Moreover, plastic relaxation is observed in the top part of the rod. Based on the experimentally obtained structural parameters, we simulate the strain-induced deformation using the finite-element method, which serves as the input for subsequent kinematic scattering simulations. The simulations reveal a significant increase of elastic in-plane relaxation along the rod height. However, at a certain height, the occurrence of plastic relaxation yields a decrease of the elastic strain. Because of the experimentally obtained structural input for the finite-element simulations, we can exclude unknown structural influences on the strain distribution, and we are able to translate the elastic relaxation into an indium concentration which increases by a factor of 4 from the bottom to the height where plastic relaxation occurs.

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publishing date
type
Contribution to journal
publication status
published
in
Physical Review Applied
volume
7
issue
2
article number
024033
publisher
American Physical Society
external identifiers
  • scopus:85014607675
ISSN
2331-7019
DOI
10.1103/PhysRevApplied.7.024033
language
English
LU publication?
no
id
1a02a22e-115b-477f-8440-824112d61404
date added to LUP
2019-10-12 12:54:03
date last changed
2023-10-07 18:59:42
@article{1a02a22e-115b-477f-8440-824112d61404,
  abstract     = {{<p>Nanofocus x-ray diffraction is used to investigate the structure and local strain field of an isolated (In,Ga)N/GaN core-shell microrod. Because the high spatial resolution of the x-ray beam is only 80×90 nm2, we are able to investigate several distinct volumes on one individual side facet. Here, we find a drastic increase in thickness of the outer GaN shell along the rod height. Additionally, we performed high-angle annular dark-field scanning-transmission-electron-microscopy measurements on several rods from the same sample showing that (In,Ga)N double-quantum-well and GaN barrier thicknesses also increase strongly along the height. Moreover, plastic relaxation is observed in the top part of the rod. Based on the experimentally obtained structural parameters, we simulate the strain-induced deformation using the finite-element method, which serves as the input for subsequent kinematic scattering simulations. The simulations reveal a significant increase of elastic in-plane relaxation along the rod height. However, at a certain height, the occurrence of plastic relaxation yields a decrease of the elastic strain. Because of the experimentally obtained structural input for the finite-element simulations, we can exclude unknown structural influences on the strain distribution, and we are able to translate the elastic relaxation into an indium concentration which increases by a factor of 4 from the bottom to the height where plastic relaxation occurs.</p>}},
  author       = {{Krause, Thilo and Hanke, Michael and Nicolai, Lars and Cheng, Zongzhe and Niehle, Michael and Trampert, Achim and Kahnt, Maik and Falkenberg, Gerald and Schroer, Christian G. and Hartmann, Jana and Zhou, Hao and Wehmann, Hergo Heinrich and Waag, Andreas}},
  issn         = {{2331-7019}},
  language     = {{eng}},
  month        = {{02}},
  number       = {{2}},
  publisher    = {{American Physical Society}},
  series       = {{Physical Review Applied}},
  title        = {{Structure and Composition of Isolated Core-Shell (In,Ga) N/GaN Rods Based on Nanofocus X-Ray Diffraction and Scanning Transmission Electron Microscopy}},
  url          = {{http://dx.doi.org/10.1103/PhysRevApplied.7.024033}},
  doi          = {{10.1103/PhysRevApplied.7.024033}},
  volume       = {{7}},
  year         = {{2017}},
}