Design and fabrication of enhanced lateral growth for dislocation reduction in GaN using nanodashes

E. D. Le Boulbar, J. Priesol, M. Nouf-Allehiani, G. Naresh-Kumar, S. Fox, C. Trager-Cowan, A. Šatka, D. W. E. Allsopp, P. A. Shields

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

The semiconductor gallium nitride is the material at the centre of energy-efficient solid-state lighting and is becoming increasingly important in high-power and high-frequency electronics. Reducing the dislocation density of gallium nitride planar layers is important for improving the performance and reliability of devices, such as light-emitting diodes and high-electron-mobility transistors. The patterning of selective growth masks is one technique for forcing a three-dimensional growth mode in order to control the propagation of threading defects to the active device layers. The morphology of the three-dimensional growth front is determined by the relative growth rates of the different facets that are formed, and for GaN is typically limited by the slow-growing {1 −1 0 1} facets. We demonstrate how the introduction of nanodash growth windows can be oriented in an array to preserve fast-growing {1 1 −2 2} facets at the early stage of growth to accelerate coalescence of three-dimensional structures into a continuous GaN layer. Cathodoluminescence and Electron Channelling Contrast Imaging methods, both used to measure the threading dislocation density, reveal that the dislocations are organised and form a distinctive pattern according to the underlying mask. By optimising the arrangement of nanodashes and the nanodash density, the threading dislocation density of GaN on sapphire epilayers can be reduced significantly from 109 cm−2 to 3.0 × 107 cm−2. Raman spectroscopy, used to monitor the strain in the overgrown GaN epilayers, shows that the position of the GaN E2H phonon mode peak was reduced as the dash density increases for a sample grown via pendeo-epitaxy whilst no obvious change was recorded for a sample grown via more conventional epitaxial lateral overgrowth. These results show how growth mask design can be used to circumvent limitations imposed by the growth dynamics. Moreover, they have revealed a greater understanding of the influence of the growth process on the dislocation density which will lead to higher performing electronic and optoelectronic devices as a result of the lower dislocation densities achieved.
LanguageEnglish
Pages30-38
Number of pages9
JournalJournal of Crystal Growth
Early online date1 Mar 2017
DOIs
Publication statusPublished - 15 May 2017

Fingerprint

Dislocations (crystals)
Fabrication
fabrication
Masks
Gallium nitride
Epilayers
flat surfaces
masks
gallium nitrides
Cathodoluminescence
Aluminum Oxide
High electron mobility transistors
Coalescence
Epitaxial growth
Sapphire
Optoelectronic devices
optoelectronic devices
cathodoluminescence
high electron mobility transistors
Light emitting diodes

Keywords

  • defects
  • metalorganic chemical vapour epitaxy
  • pendeoepitaxy
  • selective epitaxy
  • nitrides
  • semiconducting III-V materials
  • gallium nitride
  • solid-state lighting
  • cathodoluminescence
  • electron channelling contrast imaging

Cite this

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title = "Design and fabrication of enhanced lateral growth for dislocation reduction in GaN using nanodashes",
abstract = "The semiconductor gallium nitride is the material at the centre of energy-efficient solid-state lighting and is becoming increasingly important in high-power and high-frequency electronics. Reducing the dislocation density of gallium nitride planar layers is important for improving the performance and reliability of devices, such as light-emitting diodes and high-electron-mobility transistors. The patterning of selective growth masks is one technique for forcing a three-dimensional growth mode in order to control the propagation of threading defects to the active device layers. The morphology of the three-dimensional growth front is determined by the relative growth rates of the different facets that are formed, and for GaN is typically limited by the slow-growing {1 −1 0 1} facets. We demonstrate how the introduction of nanodash growth windows can be oriented in an array to preserve fast-growing {1 1 −2 2} facets at the early stage of growth to accelerate coalescence of three-dimensional structures into a continuous GaN layer. Cathodoluminescence and Electron Channelling Contrast Imaging methods, both used to measure the threading dislocation density, reveal that the dislocations are organised and form a distinctive pattern according to the underlying mask. By optimising the arrangement of nanodashes and the nanodash density, the threading dislocation density of GaN on sapphire epilayers can be reduced significantly from 109 cm−2 to 3.0 × 107 cm−2. Raman spectroscopy, used to monitor the strain in the overgrown GaN epilayers, shows that the position of the GaN E2H phonon mode peak was reduced as the dash density increases for a sample grown via pendeo-epitaxy whilst no obvious change was recorded for a sample grown via more conventional epitaxial lateral overgrowth. These results show how growth mask design can be used to circumvent limitations imposed by the growth dynamics. Moreover, they have revealed a greater understanding of the influence of the growth process on the dislocation density which will lead to higher performing electronic and optoelectronic devices as a result of the lower dislocation densities achieved.",
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author = "{Le Boulbar}, {E. D.} and J. Priesol and M. Nouf-Allehiani and G. Naresh-Kumar and S. Fox and C. Trager-Cowan and A. Šatka and Allsopp, {D. W. E.} and Shields, {P. A.}",
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Design and fabrication of enhanced lateral growth for dislocation reduction in GaN using nanodashes. / Le Boulbar, E. D.; Priesol, J. ; Nouf-Allehiani, M.; Naresh-Kumar, G.; Fox, S.; Trager-Cowan, C.; Šatka, A.; Allsopp, D. W. E.; Shields, P. A.

In: Journal of Crystal Growth, 15.05.2017, p. 30-38.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Design and fabrication of enhanced lateral growth for dislocation reduction in GaN using nanodashes

AU - Le Boulbar, E. D.

AU - Priesol, J.

AU - Nouf-Allehiani, M.

AU - Naresh-Kumar, G.

AU - Fox, S.

AU - Trager-Cowan, C.

AU - Šatka, A.

AU - Allsopp, D. W. E.

AU - Shields, P. A.

PY - 2017/5/15

Y1 - 2017/5/15

N2 - The semiconductor gallium nitride is the material at the centre of energy-efficient solid-state lighting and is becoming increasingly important in high-power and high-frequency electronics. Reducing the dislocation density of gallium nitride planar layers is important for improving the performance and reliability of devices, such as light-emitting diodes and high-electron-mobility transistors. The patterning of selective growth masks is one technique for forcing a three-dimensional growth mode in order to control the propagation of threading defects to the active device layers. The morphology of the three-dimensional growth front is determined by the relative growth rates of the different facets that are formed, and for GaN is typically limited by the slow-growing {1 −1 0 1} facets. We demonstrate how the introduction of nanodash growth windows can be oriented in an array to preserve fast-growing {1 1 −2 2} facets at the early stage of growth to accelerate coalescence of three-dimensional structures into a continuous GaN layer. Cathodoluminescence and Electron Channelling Contrast Imaging methods, both used to measure the threading dislocation density, reveal that the dislocations are organised and form a distinctive pattern according to the underlying mask. By optimising the arrangement of nanodashes and the nanodash density, the threading dislocation density of GaN on sapphire epilayers can be reduced significantly from 109 cm−2 to 3.0 × 107 cm−2. Raman spectroscopy, used to monitor the strain in the overgrown GaN epilayers, shows that the position of the GaN E2H phonon mode peak was reduced as the dash density increases for a sample grown via pendeo-epitaxy whilst no obvious change was recorded for a sample grown via more conventional epitaxial lateral overgrowth. These results show how growth mask design can be used to circumvent limitations imposed by the growth dynamics. Moreover, they have revealed a greater understanding of the influence of the growth process on the dislocation density which will lead to higher performing electronic and optoelectronic devices as a result of the lower dislocation densities achieved.

AB - The semiconductor gallium nitride is the material at the centre of energy-efficient solid-state lighting and is becoming increasingly important in high-power and high-frequency electronics. Reducing the dislocation density of gallium nitride planar layers is important for improving the performance and reliability of devices, such as light-emitting diodes and high-electron-mobility transistors. The patterning of selective growth masks is one technique for forcing a three-dimensional growth mode in order to control the propagation of threading defects to the active device layers. The morphology of the three-dimensional growth front is determined by the relative growth rates of the different facets that are formed, and for GaN is typically limited by the slow-growing {1 −1 0 1} facets. We demonstrate how the introduction of nanodash growth windows can be oriented in an array to preserve fast-growing {1 1 −2 2} facets at the early stage of growth to accelerate coalescence of three-dimensional structures into a continuous GaN layer. Cathodoluminescence and Electron Channelling Contrast Imaging methods, both used to measure the threading dislocation density, reveal that the dislocations are organised and form a distinctive pattern according to the underlying mask. By optimising the arrangement of nanodashes and the nanodash density, the threading dislocation density of GaN on sapphire epilayers can be reduced significantly from 109 cm−2 to 3.0 × 107 cm−2. Raman spectroscopy, used to monitor the strain in the overgrown GaN epilayers, shows that the position of the GaN E2H phonon mode peak was reduced as the dash density increases for a sample grown via pendeo-epitaxy whilst no obvious change was recorded for a sample grown via more conventional epitaxial lateral overgrowth. These results show how growth mask design can be used to circumvent limitations imposed by the growth dynamics. Moreover, they have revealed a greater understanding of the influence of the growth process on the dislocation density which will lead to higher performing electronic and optoelectronic devices as a result of the lower dislocation densities achieved.

KW - defects

KW - metalorganic chemical vapour epitaxy

KW - pendeoepitaxy

KW - selective epitaxy

KW - nitrides

KW - semiconducting III-V materials

KW - gallium nitride

KW - solid-state lighting

KW - cathodoluminescence

KW - electron channelling contrast imaging

UR - http://www.sciencedirect.com/science/journal/00220248

UR - http://doi.org/10.15125/BATH-00257

U2 - 10.1016/j.jcrysgro.2017.02.047

DO - 10.1016/j.jcrysgro.2017.02.047

M3 - Article

SP - 30

EP - 38

JO - Journal of Crystal Growth

T2 - Journal of Crystal Growth

JF - Journal of Crystal Growth

SN - 0022-0248

ER -