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Towards diamond transistors for the future smart grid

Hicks, Marie-Laure; (2020) Towards diamond transistors for the future smart grid. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

Diamond is the ultimate material for power electronics, with unparalleled thermal conductivity, charge carrier mobility and dielectric strength. Diamond transistors have the potential to outperform all other competing materials, predominantly silicon and silicon carbide, and provide the crucial efficiency improvements needed for the development of the future smart grid. The Horizon 2020 GreenDiamond project aims to develop the technology to build the world’s first high power diamond transistor. Within the ambitious framework of the GreenDiamond project, this work developed a surface smoothing ICP RIE Ar/O2/CF4 treatment to remove polishing induced sub-surface damage. This process produced surface roughness reduction up to 44%. An iterative and non-destructive X-ray diffraction characterisation pro- cess confirmed the effectiveness of the treatment, reducing polishing damage after a 6 μm etch and offering a potentially practical means of characterising substrates prior to epitaxial growth. The effects of the parameters of an Ar/O2 ICP RIE etch were also studied to build an effective toolkit for controlled and tailored diamond patterning. The pro- portion of oxygen in the plasma was shown to be a crucial parameter with regards to micromasking and etched surface quality. A cyclic Ar/Cl2 ICP RIE ’cleaning’ step was added to successfully achieve deep etching beyond 10 μm with near zero micromasking. Resist characteristics and undercut emerged as a potential method to control mesa wall angle. The fabrication of diamond devices can hence be con- trolled and adapted to a range of different applications, including electronics and biotechnology. Finally, MESFETs with a low boron-doped channel were produced with a top- down and bottom-up fabrication approach for the highly boron-doped Ohmic con- tact. Devices presenting current modulation and turn-off were fabricated with the bottom-up method, presenting maximum drain current up to -0.5 mA/mm, larger than values reported in the literature for diamond transistors. With these prototype devices, high performing diamond transistors are one step closer.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Towards diamond transistors for the future smart grid
Event: UCL
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: © The Author 2020. Original content in this thesis is licensed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) Licence (https://creativecommons.org/licenses/by/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request.
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng
URI: https://discovery.ucl.ac.uk/id/eprint/10090442
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