Ohmic Metallizations to Aluminum Gallium Nitride/gallium Nitride High Electron Mobility Transistors: Electrical and Microstructural Studies
Wang, Liang
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https://hdl.handle.net/2142/82821
Description
Title
Ohmic Metallizations to Aluminum Gallium Nitride/gallium Nitride High Electron Mobility Transistors: Electrical and Microstructural Studies
Author(s)
Wang, Liang
Issue Date
2008
Doctoral Committee Chair(s)
Adesida, Ilesanmi
Department of Study
Materials Science and Engineering
Discipline
Materials Science and Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Materials Science
Language
eng
Abstract
"Major findings of this work include: (1) Elucidated the interfacial reactions between Al, Ti, AlTi alloy, and Ti/Al/Mo/Au on GaN. (2) Explained the electrical performance of Ti/Al/Mo/Au on AlGaN/GaN based on microstructural investigations. Proposed a ""spike"" mechanism. (3) Identified the role of other metals, i.e. V, Mo, and Ta, as the first layer for X/Al/Mo/Au contacts. (4) Correlated the surface roughness, lateral encroachment, and contact performance of the Ti/Al/X/Au (X=Ni, Pt, Ir, Mo, Ti and NM) contacts for AlGaN/GaN HEMTs. (5) Tailored the interfacial reaction pathways and electrical performance of Ti/Al/Mo/Au on AlGaN/GaN by incorporating Si into the metallization. Obtained low-resistance contact schemes having wide processing window. (6) Investigated the electrical performance and microstructure of the Ti/Al/Mo/Au contacts on all-binary AlN/GaN HEMTs. Optimized the Ti/Al/Mo/Au contacts on n+-GaN capped AlGaN/AlN/GaN by combined surface treatment and solid state interfacial reaction. (7) Evidenced ultra-shallow Si plasma implantation and dry etch effects of SiCl4 pre-metallization treatment. Demonstrated the best performance by side-way direct contact of the metal with the 2DEG channel. (8) Characterized the carrier transport mechanism by variable temperature measurement between 100 and 375 K."
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