標題: A versatile low-resistance ohmic contact process with ohmic recess and low-temperature annealing for GaN HEMTs
作者: Lin, Yen-Ku
Bergsten, Johan
Leong, Hector
Malmros, Anna
Chen, Jr-Tai
Chen, Ding-Yuan
Kordina, Olof
Zirath, Herbert
Chang, Edward Yi
Rorsman, Niklas
材料科學與工程學系
電子工程學系及電子研究所
國際半導體學院
Department of Materials Science and Engineering
Department of Electronics Engineering and Institute of Electronics
International College of Semiconductor Technology
關鍵字: GaN;HEMT;ohmic recess;sidewall contact;gold-free;contact resistance
公開日期: 1-Sep-2018
摘要: 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.
URI: http://dx.doi.org/10.1088/1361-6641/aad7a8
http://hdl.handle.net/11536/148044
ISSN: 0268-1242
DOI: 10.1088/1361-6641/aad7a8
期刊: SEMICONDUCTOR SCIENCE AND TECHNOLOGY
Volume: 33
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