Current mapping in Graphene Contacts to AlGaN/GaN Heterostructures

Gabriele Fisichella; Giuseppe Greco; Patrick Fiorenza; Salvatore Di Franco; Fabrizio Roccaforte; Filippo Giannazzo

doi:doi:10.11648/j.nsnm.20150101.11

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Current mapping in Graphene Contacts to AlGaN/GaN Heterostructures

Gabriele Fisichella, Giuseppe Greco, Patrick Fiorenza, Salvatore Di Franco, Fabrizio Roccaforte, Filippo Giannazzo

Published in Nanoscience and Nanometrology (Volume 1, Issue 1)

Received: 5 July 2015 Accepted: 28 July 2015 Published: 29 July 2015

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Abstract

We have exploited conductive atomic force microscopy (CAFM) to characterize the vertical current transport from graphene (Gr) to the 2D electron gas of AlxGa1 xN/GaN heterostructures considering different kinds of AlGaN surfaces in terms of roughness and unevenness. The vertical current transport mechanism can radically change depending on these nanometer size superficial fluctuations whereby the nanoscale lateral resolution of CAFM current voltage (I V) measurements offers the ideal conditions to distinguish this effect form the average macroscopic behavior. We have characterized bare and Gr coated high quality AlGaN surface at first, observing for both a rectifying behavior. In particular the contact on Gr shows a lower Schottky barrier height (SBH) (ΦB = 0.4 eV) than the bare AlGaN (ΦB = 0.9 eV), and a smaller spread between the array of sampled positions. In particular this lateral homogeneity can be explained as an averaging effect of Gr on the AlGaN surface potential fluctuations over a length scale around the AFM tip in the order of the electron mean free path of a transferred CVD grown Gr (~100 nm). In order to exclude the role of the AFM metal tip force contact to the observed behavior we have performed a force dependent characterization establishing a tip force range in which this effect is negligible. We have also repeated the same characterizations on a Gr/AlGaN/GaN heterostructure with a high structured AlGaN surface. In this case a lower SBH (ΦB = 0.6 eV) and an ohmic behavior have been observed on bare AlGaN and Gr coated AlGaN respectively. This result has been attributed to the presence of preferential current paths in correspondence of the surface voids and the contemporary collection of the AFM morphology and the current map of the bare AlGaN has confirmed it. In particular, the ohmic behavior through Gr has been imputed to a contemporary lowering of the SBH and a homogenization effect of a certain density of preferential current paths

Published in	Nanoscience and Nanometrology (Volume 1, Issue 1)
DOI	10.11648/j.nsnm.20150101.11
Page(s)	1-7
Creative Commons	This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.
Copyright	Copyright © The Author(s), 2015. Published by Science Publishing Group

Keywords

Graphene, AlGaN/GaN Heterostructures, Atomic Force Microscopy, Conductive Atomic Force Microscopy

References

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APA Style

Gabriele Fisichella, Giuseppe Greco, Patrick Fiorenza, Salvatore Di Franco, Fabrizio Roccaforte, et al. (2015). Current mapping in Graphene Contacts to AlGaN/GaN Heterostructures. Nanoscience and Nanometrology, 1(1), 1-7. https://doi.org/10.11648/j.nsnm.20150101.11

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ACS Style

Gabriele Fisichella; Giuseppe Greco; Patrick Fiorenza; Salvatore Di Franco; Fabrizio Roccaforte, et al. Current mapping in Graphene Contacts to AlGaN/GaN Heterostructures. Nanosci. Nanometrol. 2015, 1(1), 1-7. doi: 10.11648/j.nsnm.20150101.11

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AMA Style

Gabriele Fisichella, Giuseppe Greco, Patrick Fiorenza, Salvatore Di Franco, Fabrizio Roccaforte, et al. Current mapping in Graphene Contacts to AlGaN/GaN Heterostructures. Nanosci Nanometrol. 2015;1(1):1-7. doi: 10.11648/j.nsnm.20150101.11

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@article{10.11648/j.nsnm.20150101.11,
  author = {Gabriele Fisichella and Giuseppe Greco and Patrick Fiorenza and Salvatore Di Franco and Fabrizio Roccaforte and Filippo Giannazzo},
  title = {Current mapping in Graphene Contacts to AlGaN/GaN Heterostructures},
  journal = {Nanoscience and Nanometrology},
  volume = {1},
  number = {1},
  pages = {1-7},
  doi = {10.11648/j.nsnm.20150101.11},
  url = {https://doi.org/10.11648/j.nsnm.20150101.11},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.nsnm.20150101.11},
  abstract = {We have exploited conductive atomic force microscopy (CAFM) to characterize the vertical current transport from graphene (Gr) to the 2D electron gas of AlxGa1 xN/GaN heterostructures considering different kinds of AlGaN surfaces in terms of roughness and unevenness. The vertical current transport mechanism can radically change depending on these nanometer size superficial fluctuations whereby the nanoscale lateral resolution of CAFM current voltage (I V) measurements offers the ideal conditions to distinguish this effect form the average macroscopic behavior. We have characterized bare and Gr coated high quality AlGaN surface at first, observing for both a rectifying behavior. In particular the contact on Gr shows a lower Schottky barrier height (SBH) (ΦB = 0.4 eV) than the bare AlGaN (ΦB = 0.9 eV), and a smaller spread between the array of sampled positions. In particular this lateral homogeneity can be explained as an averaging effect of Gr on the AlGaN surface potential fluctuations over a length scale around the AFM tip in the order of the electron mean free path of a transferred CVD grown Gr (~100 nm). In order to exclude the role of the AFM metal tip force contact to the observed behavior we have performed a force dependent characterization establishing a tip force range in which this effect is negligible. We have also repeated the same characterizations on a Gr/AlGaN/GaN heterostructure with a high structured AlGaN surface. In this case a lower SBH (ΦB = 0.6 eV) and an ohmic behavior have been observed on bare AlGaN and Gr coated AlGaN respectively. This result has been attributed to the presence of preferential current paths in correspondence of the surface voids and the contemporary collection of the AFM morphology and the current map of the bare AlGaN has confirmed it. In particular, the ohmic behavior through Gr has been imputed to a contemporary lowering of the SBH and a homogenization effect of a certain density of preferential current paths},
 year = {2015}
}

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TY  - JOUR
T1  - Current mapping in Graphene Contacts to AlGaN/GaN Heterostructures
AU  - Gabriele Fisichella
AU  - Giuseppe Greco
AU  - Patrick Fiorenza
AU  - Salvatore Di Franco
AU  - Fabrizio Roccaforte
AU  - Filippo Giannazzo
Y1  - 2015/07/29
PY  - 2015
N1  - https://doi.org/10.11648/j.nsnm.20150101.11
DO  - 10.11648/j.nsnm.20150101.11
T2  - Nanoscience and Nanometrology
JF  - Nanoscience and Nanometrology
JO  - Nanoscience and Nanometrology
SP  - 1
EP  - 7
PB  - Science Publishing Group
SN  - 2472-3630
UR  - https://doi.org/10.11648/j.nsnm.20150101.11
AB  - We have exploited conductive atomic force microscopy (CAFM) to characterize the vertical current transport from graphene (Gr) to the 2D electron gas of AlxGa1 xN/GaN heterostructures considering different kinds of AlGaN surfaces in terms of roughness and unevenness. The vertical current transport mechanism can radically change depending on these nanometer size superficial fluctuations whereby the nanoscale lateral resolution of CAFM current voltage (I V) measurements offers the ideal conditions to distinguish this effect form the average macroscopic behavior. We have characterized bare and Gr coated high quality AlGaN surface at first, observing for both a rectifying behavior. In particular the contact on Gr shows a lower Schottky barrier height (SBH) (ΦB = 0.4 eV) than the bare AlGaN (ΦB = 0.9 eV), and a smaller spread between the array of sampled positions. In particular this lateral homogeneity can be explained as an averaging effect of Gr on the AlGaN surface potential fluctuations over a length scale around the AFM tip in the order of the electron mean free path of a transferred CVD grown Gr (~100 nm). In order to exclude the role of the AFM metal tip force contact to the observed behavior we have performed a force dependent characterization establishing a tip force range in which this effect is negligible. We have also repeated the same characterizations on a Gr/AlGaN/GaN heterostructure with a high structured AlGaN surface. In this case a lower SBH (ΦB = 0.6 eV) and an ohmic behavior have been observed on bare AlGaN and Gr coated AlGaN respectively. This result has been attributed to the presence of preferential current paths in correspondence of the surface voids and the contemporary collection of the AFM morphology and the current map of the bare AlGaN has confirmed it. In particular, the ohmic behavior through Gr has been imputed to a contemporary lowering of the SBH and a homogenization effect of a certain density of preferential current paths
VL  - 1
IS  - 1
ER  -

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Author Information

Gabriele Fisichella

Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi, Catania, Italy
Giuseppe Greco

Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi, Catania, Italy
Patrick Fiorenza

Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi, Catania, Italy
Salvatore Di Franco

Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi, Catania, Italy
Fabrizio Roccaforte

Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi, Catania, Italy
Filippo Giannazzo

Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi, Catania, Italy

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APA Style

Gabriele Fisichella, Giuseppe Greco, Patrick Fiorenza, Salvatore Di Franco, Fabrizio Roccaforte, et al. (2015). Current mapping in Graphene Contacts to AlGaN/GaN Heterostructures. Nanoscience and Nanometrology, 1(1), 1-7. https://doi.org/10.11648/j.nsnm.20150101.11

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ACS Style

Gabriele Fisichella; Giuseppe Greco; Patrick Fiorenza; Salvatore Di Franco; Fabrizio Roccaforte, et al. Current mapping in Graphene Contacts to AlGaN/GaN Heterostructures. Nanosci. Nanometrol. 2015, 1(1), 1-7. doi: 10.11648/j.nsnm.20150101.11

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AMA Style

Gabriele Fisichella, Giuseppe Greco, Patrick Fiorenza, Salvatore Di Franco, Fabrizio Roccaforte, et al. Current mapping in Graphene Contacts to AlGaN/GaN Heterostructures. Nanosci Nanometrol. 2015;1(1):1-7. doi: 10.11648/j.nsnm.20150101.11

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@article{10.11648/j.nsnm.20150101.11,
  author = {Gabriele Fisichella and Giuseppe Greco and Patrick Fiorenza and Salvatore Di Franco and Fabrizio Roccaforte and Filippo Giannazzo},
  title = {Current mapping in Graphene Contacts to AlGaN/GaN Heterostructures},
  journal = {Nanoscience and Nanometrology},
  volume = {1},
  number = {1},
  pages = {1-7},
  doi = {10.11648/j.nsnm.20150101.11},
  url = {https://doi.org/10.11648/j.nsnm.20150101.11},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.nsnm.20150101.11},
  abstract = {We have exploited conductive atomic force microscopy (CAFM) to characterize the vertical current transport from graphene (Gr) to the 2D electron gas of AlxGa1 xN/GaN heterostructures considering different kinds of AlGaN surfaces in terms of roughness and unevenness. The vertical current transport mechanism can radically change depending on these nanometer size superficial fluctuations whereby the nanoscale lateral resolution of CAFM current voltage (I V) measurements offers the ideal conditions to distinguish this effect form the average macroscopic behavior. We have characterized bare and Gr coated high quality AlGaN surface at first, observing for both a rectifying behavior. In particular the contact on Gr shows a lower Schottky barrier height (SBH) (ΦB = 0.4 eV) than the bare AlGaN (ΦB = 0.9 eV), and a smaller spread between the array of sampled positions. In particular this lateral homogeneity can be explained as an averaging effect of Gr on the AlGaN surface potential fluctuations over a length scale around the AFM tip in the order of the electron mean free path of a transferred CVD grown Gr (~100 nm). In order to exclude the role of the AFM metal tip force contact to the observed behavior we have performed a force dependent characterization establishing a tip force range in which this effect is negligible. We have also repeated the same characterizations on a Gr/AlGaN/GaN heterostructure with a high structured AlGaN surface. In this case a lower SBH (ΦB = 0.6 eV) and an ohmic behavior have been observed on bare AlGaN and Gr coated AlGaN respectively. This result has been attributed to the presence of preferential current paths in correspondence of the surface voids and the contemporary collection of the AFM morphology and the current map of the bare AlGaN has confirmed it. In particular, the ohmic behavior through Gr has been imputed to a contemporary lowering of the SBH and a homogenization effect of a certain density of preferential current paths},
 year = {2015}
}

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TY  - JOUR
T1  - Current mapping in Graphene Contacts to AlGaN/GaN Heterostructures
AU  - Gabriele Fisichella
AU  - Giuseppe Greco
AU  - Patrick Fiorenza
AU  - Salvatore Di Franco
AU  - Fabrizio Roccaforte
AU  - Filippo Giannazzo
Y1  - 2015/07/29
PY  - 2015
N1  - https://doi.org/10.11648/j.nsnm.20150101.11
DO  - 10.11648/j.nsnm.20150101.11
T2  - Nanoscience and Nanometrology
JF  - Nanoscience and Nanometrology
JO  - Nanoscience and Nanometrology
SP  - 1
EP  - 7
PB  - Science Publishing Group
SN  - 2472-3630
UR  - https://doi.org/10.11648/j.nsnm.20150101.11
AB  - We have exploited conductive atomic force microscopy (CAFM) to characterize the vertical current transport from graphene (Gr) to the 2D electron gas of AlxGa1 xN/GaN heterostructures considering different kinds of AlGaN surfaces in terms of roughness and unevenness. The vertical current transport mechanism can radically change depending on these nanometer size superficial fluctuations whereby the nanoscale lateral resolution of CAFM current voltage (I V) measurements offers the ideal conditions to distinguish this effect form the average macroscopic behavior. We have characterized bare and Gr coated high quality AlGaN surface at first, observing for both a rectifying behavior. In particular the contact on Gr shows a lower Schottky barrier height (SBH) (ΦB = 0.4 eV) than the bare AlGaN (ΦB = 0.9 eV), and a smaller spread between the array of sampled positions. In particular this lateral homogeneity can be explained as an averaging effect of Gr on the AlGaN surface potential fluctuations over a length scale around the AFM tip in the order of the electron mean free path of a transferred CVD grown Gr (~100 nm). In order to exclude the role of the AFM metal tip force contact to the observed behavior we have performed a force dependent characterization establishing a tip force range in which this effect is negligible. We have also repeated the same characterizations on a Gr/AlGaN/GaN heterostructure with a high structured AlGaN surface. In this case a lower SBH (ΦB = 0.6 eV) and an ohmic behavior have been observed on bare AlGaN and Gr coated AlGaN respectively. This result has been attributed to the presence of preferential current paths in correspondence of the surface voids and the contemporary collection of the AFM morphology and the current map of the bare AlGaN has confirmed it. In particular, the ohmic behavior through Gr has been imputed to a contemporary lowering of the SBH and a homogenization effect of a certain density of preferential current paths
VL  - 1
IS  - 1
ER  -

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