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Scanning capacitance microscopy of GaN-based high electron mobility transistor structures: A practical guide
,
Saptarsi Ghosh ,
Francesca Adams,
Menno J. Kappers,
David J. Wallis,
Rachel A. Oliver
Ultramicroscopy, Volume: 254, Start page: 113833
Swansea University Author:
Saptarsi Ghosh
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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...
| Published in: | Ultramicroscopy |
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| ISSN: | 0304-3991 |
| Published: |
Elsevier BV
2023
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| Online Access: |
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| URI: | https://cronfa.swan.ac.uk/Record/cronfa66866 |
| 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 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. |
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| Keywords: |
Scanning capacitance microscopy; High electron mobility transistor structures; Plan-view characterisation |
| College: |
Faculty of Science and Engineering |
| Funders: |
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
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113833 |