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Structural investigation of ultra-low resistance deeply recessed sidewall ohmic contacts for AlGaN/GaN HEMTs based on Ti/Al/Ti-metallization
SweGaN AB, Linkoping, Sweden; Chalmers Univ Technol, Sweden.
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. (C3NiT-Janzen)ORCID iD: 0000-0002-0399-8369
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. TheMAC, Sweden; Lund Univ, Sweden; Lund Univ, Sweden. (C3NiT-Janzen)ORCID iD: 0000-0002-8112-7411
Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.ORCID iD: 0000-0001-9140-6724
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2023 (English)In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 38, no 10, article id 105006Article in journal (Refereed) Published
Abstract [en]

This study presents a novel approach to forming low-resistance ohmic contacts for AlGaN/GaN HEMTs. The optimized contacts exhibit an outstanding contact resistance of approximately 0.15 & omega;& BULL;mm. This is achieved by firstly recessing the barrier of the heterostructure to a depth beyond the channel. In this way, the channel region is exposed on the sidewall of the recess. The coverage of the Ti/Al/Ti ohmic metalization on the sidewall is ensured through tilting of the sample during evaporation. The annealing process is performed at a low temperature of 550 & DEG;C. The approach does not require precise control of the recess etching. Furthermore, the method is directly applicable to most barrier designs in terms of thickness and Al-concentration. The impact of recessed sidewall angle, thickness and ratio of Ti and Al layers, and the annealing procedure are investigated. Structural and chemical analyses of the interface between the ohmic contacts and epi-structure indicate the formation of ohmic contacts by the extraction of nitrogen from the epi-structure. The approach is demonstrated on HEMT-structures with two different barrier designs in terms of Al-concentration and barrier thickness. The study demonstrate large process window in regard to recess depth and duration of the annealing as well as high uniformity of the contact resistance across the samples, rendering the approach highly suitable for industrial production processes.

Place, publisher, year, edition, pages
IOP Publishing Ltd , 2023. Vol. 38, no 10, article id 105006
Keywords [en]
AlGaN/GaN HEMTs; ohmic contact; annealing temperatures; recessed; sidewall
National Category
Other Materials Engineering
Identifiers
URN: urn:nbn:se:liu:diva-197852DOI: 10.1088/1361-6641/acf396ISI: 001058572800001OAI: oai:DiVA.org:liu-197852DiVA, id: diva2:1798144
Note

Funding Agencies|Swedish Governmental Agency for Innovation Systems (VINNOVA); Linkoeping University; Chalmers University; ABB [2016-05190]; Epiluvac; Ericsson; FMV; Gotmic; Region Skane; Saab; SweGaN; Volvo Cars; United Monolithic Semiconductors (UMS); project Ultra-Compact AESA Technology for Autonomous Aircrafts; VINNOVA; Saab AB; project CoolHEMT; European Unions Horizon 2020 research and innovation programme [2017-04870]; Swedish Foundation for Strategic Research; Knut and Alice Wallenberg foundation; ARTEMI [823260]; Swedish National Infrastructure in Advanced Electron Microscopy - Swedish Research Council [EM16-0024, STP19-0008]; Foundation for strategic research; [2021-00171]; [RIF21-0026]

Available from: 2023-09-18 Created: 2023-09-18 Last updated: 2023-12-28

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