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A versatile low-resistance ohmic contact process with ohmic recess and low-temperature annealing for GaN HEMTs
Natl Chiao Tung Univ, Taiwan.
Chalmers Univ Technol, Sweden.
Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
Chalmers Univ Technol, Sweden.
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2018 (English)In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 33, no 9, article id 095019Article in journal (Refereed) Published
Abstract [en]

Deeply recessed ohmic contacts for GaN-based high electron mobility transistors (HEMTs) are demonstrated. It is shown that low-resistance ohmic contacts can be achieved with recessing beyond the AlGaN Schottky barrier where the ohmic contacts are formed on the sidewall of the recess. This makes the process versatile and relatively insensitive to the exact recess depth. The ohmic contact is based on a gold-free metallization scheme consisting of a Ta/Al/Ta metal stack requiring a low-temperature annealing. Important parameters for this type of ohmic contact process include the metal coverage, slope of the etched sidewall, bottom Ta-layer thickness, as well as annealing temperature and duration. The optimized contact resistance is as low as 0.24 Omega mm after annealing at 575 degrees C. Moreover, this sidewall contact approach was successfully implemented on different epitaxial heterostructures with different AlGaN barrier thickness as well as with and without AlN exclusion layer. All the samples exhibited excellent contact resistances in a wide range of recess depths. The Ta-based, sidewall ohmic contact process is a promising method for forming an ohmic contact on a wide range of GaN HEMT epitaxial designs.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD , 2018. Vol. 33, no 9, article id 095019
Keywords [en]
GaN; HEMT; ohmic recess; sidewall contact; gold-free; contact resistance
National Category
Other Materials Engineering
Identifiers
URN: urn:nbn:se:liu:diva-151197DOI: 10.1088/1361-6641/aad7a8ISI: 000442448200001OAI: oai:DiVA.org:liu-151197DiVA, id: diva2:1248048
Note

Funding Agencies|Swedish Governmental Agency for Innovation Systems (VINNOVA) [2016-05190]; Linkoping University; Chalmers University; ABB; Epiluvac; Ericsson; FMV; Gotmic; On Semiconductor; Saab; SweGaN; United Monolithic Semiconductors (UMS); Center for Semiconductor Technology Research from The Featured Areas Research Center Program by the Ministry of Education (MOE) in Taiwan; Ministry of Science and Technology, Taiwan [MOST-107-3017-F-009-002]; National Chung-Shan Institute of Science and Technology, Taiwan [NCSIST-104-V412 (107)]

Available from: 2018-09-13 Created: 2018-09-13 Last updated: 2018-09-13

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