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Impact of AlGaN/GaN interface sharpness on HEMT performance
Microwave Electronics Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, Göteborg, Sweden.
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
Microwave Electronics Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, Göteborg, Sweden.
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

The impact of the design and sharpness of the AlGaN/GaN interface in GaN-based HEMTs is investigated. Three structures with different AlGaN/GaN interface properties were grown with hot-wall MOCVD. One structure has a 2-nmthick AlN exclusion layer in between the AlGaN and the GaN, while the other two differ in their sharpness of the Al transition at the AlGaN/GaN interface. The structures with AlN exclusion layer and optimized sharpness of the interface show similar electron mobilities (1760 and 1740 cm2/Vs). HEMTs were processed and evaluated. Gated Hall-measurements indicate that the sharper interface maintains a higher mobility when the electrons are close to the interface compared both to the AlNexclusion layer and the non-optimized structure. The higher mobility manifests as lower parasitic resistance yielding better DC and high frequency performance. Pulsed IV measurements indicate that the sharper interface provide less dispersive effects compared both to the AlN exclusion layer and the optimized interface.

Keyword [en]
GaN HEMT, AlGaN/GaN interface, sharpness
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:liu:diva-117137OAI: oai:DiVA.org:liu-117137DiVA: diva2:805920
Available from: 2015-04-17 Created: 2015-04-17 Last updated: 2015-04-17Bibliographically approved
In thesis
1. MOCVD growth of GaN-based high electron mobility transistor structures
Open this publication in new window or tab >>MOCVD growth of GaN-based high electron mobility transistor structures
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The present work was to improve the overall quality of GaN-based high electron mobility transistor (HEMT) epitaxial structures grown on semi-insulating (SI) SiC and native GaN substrates, using an approach called bottom-to-top optimization. The bottom-to-top optimization means an entire growth process optimization, from in-situ substrate pretreatment to the epitaxial growth and then the cooling process. Great effort was put to gain the understanding of the influence of growth parameters on material properties and consequently to establish an advanced and reproducible growth process. Many state-of-the-art material properties of GaN-based HEMT structures were achieved in this work, including superior structural integrity of AlN nucleation layers for ultra-low thermal boundary resistance, excellent control of residual impurities, outstanding and nearly-perfect crystalline quality of GaN epilayers grown on SiC and native GaN substrates, respectively, and record-high room temperature 2DEG mobility obtained in simple AlGaN/GaN heterostructures.

The epitaxial growth of the wide bandgap III-nitride epilayers like GaN, AlN,  AlGaN, and InAlN, as well as various GaN-based HEMT structures was all carried out in a hot-wall metalorganic chemical vapor deposition (MOCVD) system. A variety of structural and electrical characterizations were routinely used to provide fast feedback for adjusting growth parameters and developing improved growth processes.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2015. 59 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1662
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-117138 (URN)10.3384/diss.diva-117138 (DOI)978-91-7519-073-0 (ISBN)
Public defence
2015-05-12, Planck, Fysikhuset, Campus Valla, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2015-04-17 Created: 2015-04-17 Last updated: 2015-04-17Bibliographically approved

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Chen, Jr-TaiForsberg, UrbanJanzén, Erik

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