The role of selective pattern etching to improve the Ohmic contact resistance and device performance of AlGaN/GaN HEMTs

Dhongde, A., Taking, S., Elksne, M. , Samanta, S. , Ofiare, A., Karami, K. , Al-Khalidi, A. and Wasige, E. (2021) The role of selective pattern etching to improve the Ohmic contact resistance and device performance of AlGaN/GaN HEMTs. International Journal of Nanoelectronics and Materials, 14, pp. 21-28.

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In this work, we report the processing and DC performance of fabricated AlGaN/GaN HEMT devices using 3 different patterned Ohmic contact structures. The types of Ohmic contact patterns used are horizontal, vertical and chess. A device with a conventional Ohmic contact was also fabricated for comparison. Two different etch depths were investigated, a ~ 9 nm and ~ 30 nm for a shallow and deep Ohmic recess etching, respectively. The lowest contact resistance of 0.32 Ω.mm was observed for a deep horizontal patterned structure. The fabricated device with this structure also demonstrated the highest maximum saturation drain current of 1285 mA/mm and maximum transconductance of 296 mS/mm compared to other devices. The horizontal patterned structure utilizes the uneven AlGaN layer thickness underneath the Ohmic metal contacts. The formation of sidewall areas on AlGaN surface during the patterned etching process provides better contact of Ohmic metal resulting in more tunnelling current between the Ohmic metal and AlGaN barrier thus reducing the contact resistance. This approach also provides the lowest contact resistance due to removal of AlGaN barrier layer (patterned etching) and it is in parallel with the lateral current of the 2DEG resulting in better tunnelling current compared to the vertical and chess patterned structures. The contact resistance can be further improved by optimization the etching depth prior to Ohmic metal deposition. The results indicate the potential of the Ohmic patterned etching structure to further improving the performance of GaN devices.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Samanta, Dr Swagata and Karami, Mr Kaivan and Taking, Dr Sanna and Ofiare, Dr Afesomeh and Al-Khalidi, Dr Abdullah and Wasige, Professor Edward and Elksne, Mrs Maira and Dhongde, Aniket
Authors: Dhongde, A., Taking, S., Elksne, M., Samanta, S., Ofiare, A., Karami, K., Al-Khalidi, A., and Wasige, E.
College/School:College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
Journal Name:International Journal of Nanoelectronics and Materials
Publisher:Universiti Malaysia Perlis (UniMAP)
ISSN (Online):1997-4434
Copyright Holders:Copyright © 2021 Universiti Malaysia Perlis (UniMAP)
First Published:First published in International Journal of Nanoelectronics and Materials 14:21-28
Publisher Policy:Reproduced with the permission of the publisher

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
301178Novel GaN Power Devices and Packaging Technologies for 300 degC Ambient OperationEdward WasigeEngineering and Physical Sciences Research Council (EPSRC)EP/R024413/1ENG - Electronics & Nanoscale Engineering