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Proceedings Paper

Effect of substrate offcut on AlGaN/GaN HFET structures on bulk GaN substrates
Author(s): J. H. Leach; N. Biswas; T. Paskova; E. A. Preble; K. R. Evans; M. Wu; X. Ni; X. Li; Ü. Özgür; H. Morkoç
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Paper Abstract

Bulk GaN substrates promise to bring the full potential of nitride-based devices to bear since they offer a low thermal and lattice mismatched alternative to foreign substrates for epitaxial growth. However, due to the high cost and low availability of bulk GaN substrates, effects such as surface misorientation (offcut), surface polishing, and preparation of such substrates on subsequent epitaxy are still not well understood. As such, AlGaN/GaN heterostructures with nominal Al compositions of 25% were grown by MOCVD on semi-insulating bulk GaN substrates with offcuts ranging from 0.05 to 1.95° in the m-direction (10 10) to attempt to determine the optimal offcut for bulk GaN substrates for AlGaN-based HFET devices. X-ray diffraction (XRD) studies indicate that the Al composition does not vary with offcut, however reciprocal space mapping shows evidence of strain relaxation of the AlGaN in samples grown on substrates with offcut >1.1°. Additionally, we observed a minimum in sheet resistance of the 2DEGs for substrates with offcuts near 0.5°, arising from higher mobilities in these samples. Evidence of an optimal substrate misorientation is important for AlGaN-based devices grown on bulk GaN substrates.

Paper Details

Date Published: 4 March 2011
PDF: 6 pages
Proc. SPIE 7939, Gallium Nitride Materials and Devices VI, 79390E (4 March 2011); doi: 10.1117/12.875755
Show Author Affiliations
J. H. Leach, Kyma Technologies, Inc. (United States)
Virginia Commonwealth Univ. (United States)
N. Biswas, Kyma Technologies, Inc. (United States)
T. Paskova, Kyma Technologies, Inc. (United States)
E. A. Preble, Kyma Technologies, Inc. (United States)
K. R. Evans, Kyma Technologies, Inc. (United States)
M. Wu, Virginia Commonwealth Univ. (United States)
X. Ni, Virginia Commonwealth Univ. (United States)
X. Li, Virginia Commonwealth Univ. (United States)
Ü. Özgür, Virginia Commonwealth Univ. (United States)
H. Morkoç, Virginia Commonwealth Univ. (United States)


Published in SPIE Proceedings Vol. 7939:
Gallium Nitride Materials and Devices VI
Jen-Inn Chyi; Yasushi Nanishi; Hadis Morkoç; Joachim Piprek; Euijoon Yoon, Editor(s)

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