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Local defect-enhanced anodic oxidation of reformed GaN nanowires

Colvin, Jovana LU ; Ciechonski, Rafal ; Gustafsson, Anders LU orcid ; Samuelson, Lars LU ; Ohlsson, B. Jonas and Timm, Rainer LU orcid (2020) In Physical Review Materials 4(7).
Abstract
Understanding formation and distribution of defects in GaN substrates and device layers is needed to improve device performance in rf and power electronics. Here we utilize conductive atomic force microscopy (c-AFM) for studying defect-related leakage paths in an unintentionally doped GaN film formed by nanowire reformation. A nanoscopic Schottky contact is formed between the c-AFM probe and the GaN surface, which, under reverse-bias conditions, reveals local leakage currents at the positions of the nanowires. Cathodoluminescence shows these areas to be dominated by yellow-band luminescence, in contrast to the surrounding GaN matrix, which mainly shows near-band-gap luminescence. These results are attributed to a high density of native and... (More)
Understanding formation and distribution of defects in GaN substrates and device layers is needed to improve device performance in rf and power electronics. Here we utilize conductive atomic force microscopy (c-AFM) for studying defect-related leakage paths in an unintentionally doped GaN film formed by nanowire reformation. A nanoscopic Schottky contact is formed between the c-AFM probe and the GaN surface, which, under reverse-bias conditions, reveals local leakage currents at the positions of the nanowires. Cathodoluminescence shows these areas to be dominated by yellow-band luminescence, in contrast to the surrounding GaN matrix, which mainly shows near-band-gap luminescence. These results are attributed to a high density of native and residual defects, confined to the nanowires. In addition, we use anodic oxidation to map defect-related conductive paths through locally induced growth of gallium oxide. The oxide yield, which is known to depend on the local electric field strength between the AFM tip and the sample, correlates well with the level of reverse-bias leakage current. Local irregularities in oxide height reveal extended oxidation attributed to defect-related deep-level states. This
is confirmed by controlled dissolution of the oxide in NaOH, showing that a deeper oxide film is grown over areas where defect-related conductive paths are formed. Finally, we demonstrate how this approach can be used as a quick and easy diagnostic tool for evaluating the influence of specific growth conditions and process steps on defect-induced leakage current levels and defect distribution in GaN structures, demonstrating its potential for accelerated test of leakage degradation at critical positions in GaN-based devices. (Less)
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author
; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Physical Review Materials
volume
4
issue
7
article number
074603
pages
7 pages
publisher
American Physical Society
external identifiers
  • scopus:85092932368
ISSN
2475-9953
DOI
10.1103/PhysRevMaterials.4.074603
language
English
LU publication?
yes
id
8c17ae7c-f7f8-4151-8ddb-f5639986369e
date added to LUP
2020-07-30 15:08:24
date last changed
2023-10-17 15:52:53
@article{8c17ae7c-f7f8-4151-8ddb-f5639986369e,
  abstract     = {{Understanding formation and distribution of defects in GaN substrates and device layers is needed to improve device performance in rf and power electronics. Here we utilize conductive atomic force microscopy (c-AFM) for studying defect-related leakage paths in an unintentionally doped GaN film formed by nanowire reformation. A nanoscopic Schottky contact is formed between the c-AFM probe and the GaN surface, which, under reverse-bias conditions, reveals local leakage currents at the positions of the nanowires. Cathodoluminescence shows these areas to be dominated by yellow-band luminescence, in contrast to the surrounding GaN matrix, which mainly shows near-band-gap luminescence. These results are attributed to a high density of native and residual defects, confined to the nanowires. In addition, we use anodic oxidation to map defect-related conductive paths through locally induced growth of gallium oxide. The oxide yield, which is known to depend on the local electric field strength between the AFM tip and the sample, correlates well with the level of reverse-bias leakage current. Local irregularities in oxide height reveal extended oxidation attributed to defect-related deep-level states. This<br/>is confirmed by controlled dissolution of the oxide in NaOH, showing that a deeper oxide film is grown over areas where defect-related conductive paths are formed. Finally, we demonstrate how this approach can be used as a quick and easy diagnostic tool for evaluating the influence of specific growth conditions and process steps on defect-induced leakage current levels and defect distribution in GaN structures, demonstrating its potential for accelerated test of leakage degradation at critical positions in GaN-based devices.}},
  author       = {{Colvin, Jovana and Ciechonski, Rafal and Gustafsson, Anders and Samuelson, Lars and Ohlsson, B. Jonas and Timm, Rainer}},
  issn         = {{2475-9953}},
  language     = {{eng}},
  month        = {{07}},
  number       = {{7}},
  publisher    = {{American Physical Society}},
  series       = {{Physical Review Materials}},
  title        = {{Local defect-enhanced anodic oxidation of reformed GaN nanowires}},
  url          = {{http://dx.doi.org/10.1103/PhysRevMaterials.4.074603}},
  doi          = {{10.1103/PhysRevMaterials.4.074603}},
  volume       = {{4}},
  year         = {{2020}},
}