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Scanning capacitance microscopy of GaN-based high electron mobility transistor structures: A practical guide

Chen Chen Orcid Logo, Saptarsi Ghosh Orcid Logo, Francesca Adams, Menno J. Kappers, David J. Wallis, Rachel A. Oliver

Ultramicroscopy, Volume: 254, Start page: 113833

Swansea University Author: Saptarsi Ghosh Orcid Logo

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DOI (Published version): 10.1016/j.ultramic.2023.113833

Abstract

The scanning capacitance microscope (SCM) is a powerful tool to characterise local electrical properties in GaN-based high electron mobility transistor (HEMT) structures with nanoscale resolution. We investigated the experimental setup and the imaging conditions to optimise the SCM contrast. As to t...

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Published in: Ultramicroscopy
ISSN: 0304-3991
Published: Elsevier BV 2023
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URI: https://cronfa.swan.ac.uk/Record/cronfa66866
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As to the experimental setup, we show that the desired tip should be sharp (e.g., with the tip radius of ) and its coating should be made of conductive doped diamond. Most importantly, its spring constant should be large to achieve stable tip-sample contact. The selected tip should be positioned close to both the edge and Ohmic contact of the sample. Regarding the imaging conditions, we also show that a dc bias should be applied in addition to an ac bias because the latter alone is not sufficient to deplete the two-dimensional electron gas (2DEG) in the AlGaN/GaN heterostructure. The approximate range of the effective dc bias values was found by measuring the local dC/dV-V curves, yielding, after further optimisation, two optimised dc bias values which provide strong, but opposite, SCM contrast. In comparison, the selected ac bias value has no significant impact on the SCM contrast. 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spelling 2024-08-15T11:43:03.6417231 v2 66866 2024-06-23 Scanning capacitance microscopy of GaN-based high electron mobility transistor structures: A practical guide 3e247ecabd6eddd319264d066b0ce959 0000-0003-1685-6228 Saptarsi Ghosh Saptarsi Ghosh true false 2024-06-23 ACEM The scanning capacitance microscope (SCM) is a powerful tool to characterise local electrical properties in GaN-based high electron mobility transistor (HEMT) structures with nanoscale resolution. We investigated the experimental setup and the imaging conditions to optimise the SCM contrast. As to the experimental setup, we show that the desired tip should be sharp (e.g., with the tip radius of ) and its coating should be made of conductive doped diamond. Most importantly, its spring constant should be large to achieve stable tip-sample contact. The selected tip should be positioned close to both the edge and Ohmic contact of the sample. Regarding the imaging conditions, we also show that a dc bias should be applied in addition to an ac bias because the latter alone is not sufficient to deplete the two-dimensional electron gas (2DEG) in the AlGaN/GaN heterostructure. The approximate range of the effective dc bias values was found by measuring the local dC/dV-V curves, yielding, after further optimisation, two optimised dc bias values which provide strong, but opposite, SCM contrast. In comparison, the selected ac bias value has no significant impact on the SCM contrast. The described methodology could potentially also be applied to other types of HEMT structures, and highly-doped samples. Journal Article Ultramicroscopy 254 113833 Elsevier BV 0304-3991 Scanning capacitance microscopy; High electron mobility transistor structures; Plan-view characterisation 1 12 2023 2023-12-01 10.1016/j.ultramic.2023.113833 COLLEGE NANME Aerospace, Civil, Electrical, and Mechanical Engineering COLLEGE CODE ACEM Swansea University External research funder(s) paid the OA fee (includes OA grants disbursed by the Library) The authors would like to thank Dr Peter De Wolf and Dr Vishal Panchal from Bruker Nano Surfaces & Metrology for fruitful discussions and support. C. Chen would like to thank China Scholarship Council, China and Cambridge Commonwealth, European & International Trust, United Kingdom for a CSC Cambridge Scholarship. Materials studied here were grown using the EPSRC National Epitaxy Facility, United Kingdom under EPSRC Grant EP/N017927/1 . The access to the AFM was supported under Cambridge Royce facilities, United Kingdom grant EP/P024947/1 and Sir Henry Royce Institute, United Kingdom recurrent grant EP/R00661X/1 . 2024-08-15T11:43:03.6417231 2024-06-23T19:49:29.9033510 Faculty of Science and Engineering School of Aerospace, Civil, Electrical, General and Mechanical Engineering - Electronic and Electrical Engineering Chen Chen 0000-0001-9931-2650 1 Saptarsi Ghosh 0000-0003-1685-6228 2 Francesca Adams 3 Menno J. Kappers 4 David J. Wallis 5 Rachel A. Oliver 6 66866__31122__ae1ed5cfedb94c04a9543f6e89b6b94a.pdf 66866.VoR.pdf 2024-08-15T11:41:45.0439179 Output 4514159 application/pdf Version of Record true © 2023 The Author(s). This is an open access article under the CC BY license. true eng http://creativecommons.org/licenses/by/4.0/
title Scanning capacitance microscopy of GaN-based high electron mobility transistor structures: A practical guide
spellingShingle Scanning capacitance microscopy of GaN-based high electron mobility transistor structures: A practical guide
Saptarsi Ghosh
title_short Scanning capacitance microscopy of GaN-based high electron mobility transistor structures: A practical guide
title_full Scanning capacitance microscopy of GaN-based high electron mobility transistor structures: A practical guide
title_fullStr Scanning capacitance microscopy of GaN-based high electron mobility transistor structures: A practical guide
title_full_unstemmed Scanning capacitance microscopy of GaN-based high electron mobility transistor structures: A practical guide
title_sort Scanning capacitance microscopy of GaN-based high electron mobility transistor structures: A practical guide
author_id_str_mv 3e247ecabd6eddd319264d066b0ce959
author_id_fullname_str_mv 3e247ecabd6eddd319264d066b0ce959_***_Saptarsi Ghosh
author Saptarsi Ghosh
author2 Chen Chen
Saptarsi Ghosh
Francesca Adams
Menno J. Kappers
David J. Wallis
Rachel A. Oliver
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container_title Ultramicroscopy
container_volume 254
container_start_page 113833
publishDate 2023
institution Swansea University
issn 0304-3991
doi_str_mv 10.1016/j.ultramic.2023.113833
publisher Elsevier BV
college_str Faculty of Science and Engineering
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hierarchy_top_title Faculty of Science and Engineering
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department_str School of Aerospace, Civil, Electrical, General and Mechanical Engineering - Electronic and Electrical Engineering{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Aerospace, Civil, Electrical, General and Mechanical Engineering - Electronic and Electrical Engineering
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description The scanning capacitance microscope (SCM) is a powerful tool to characterise local electrical properties in GaN-based high electron mobility transistor (HEMT) structures with nanoscale resolution. We investigated the experimental setup and the imaging conditions to optimise the SCM contrast. As to the experimental setup, we show that the desired tip should be sharp (e.g., with the tip radius of ) and its coating should be made of conductive doped diamond. Most importantly, its spring constant should be large to achieve stable tip-sample contact. The selected tip should be positioned close to both the edge and Ohmic contact of the sample. Regarding the imaging conditions, we also show that a dc bias should be applied in addition to an ac bias because the latter alone is not sufficient to deplete the two-dimensional electron gas (2DEG) in the AlGaN/GaN heterostructure. The approximate range of the effective dc bias values was found by measuring the local dC/dV-V curves, yielding, after further optimisation, two optimised dc bias values which provide strong, but opposite, SCM contrast. In comparison, the selected ac bias value has no significant impact on the SCM contrast. The described methodology could potentially also be applied to other types of HEMT structures, and highly-doped samples.
published_date 2023-12-01T08:26:12Z
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