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AlGaN Transition Layers on Si (111) Substrates - Observations of Microstructure and Impact on Material Quality

Published online by Cambridge University Press:  01 February 2011

John C. Roberts ,
James W. Cook Jr. ,
Pradeep Rajagopal ,
Edwin L. Piner  and
Kevin J. Linthicum
John C. Roberts
Affiliation:
[email protected], Nitronex Corporation, Fab, 2305 Presidential Drive, Durham, NC, 27278, United States, 9194245212
James W. Cook Jr.
Affiliation:
[email protected], Nitronex Corporation, 2305 Presidential Drive, Durham, NC, 27703, United States
Pradeep Rajagopal
Affiliation:
[email protected], Nitronex Corporation, 2305 Presidential Drive, Durham, NC, 27703, United States
Edwin L. Piner
Affiliation:
[email protected], Nitronex Corporation, 2305 Presidential Drive, Durham, NC, 27703, United States
Kevin J. Linthicum
Affiliation:
[email protected], Nitronex Corporation, 2305 Presidential Drive, Durham, NC, 27703, United States
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Abstract

III-nitride materials have different crystal structures and properties than the substrates commonly used for their deposition, including silicon, silicon carbide and sapphire. These differences, such as thermal expansion coefficient and lattice constant, necessitate the use of a transition layer to accommodate the resulting stress between substrate and the epitaxially grown III-N layers. AlxGa1−xN based transition layers are one proven solution used for the growth of device quality GaN layers on Si (111) substrates. The use of such transition layers enables the deposition of state of the art AlGaN/GaN high electron mobility transistor epitaxial structures that, upon fabrication into devices, exhibit high performance and excellent reliability.

Examination of the microstructure of these AlxGa1−xN transition layers, by transmission electron microscopy (TEM) and other methods, reveals some interesting properties that can help explain how high quality III-N epitaxy can be performed in a system with significant thermal and lattice mismatch. Observations that will be reported on and discussed in this presentation are (1) the role that a thin strain absorbing amorphous SiNx layer at the Si substrate/transition layer interface plays in the reduction of the formation of misfit dislocations, (2) the low screw dislocation density (less than ȼ107/cm2) in these III-N films relative to edge and mixed dislocation densities, and (3) the role that the substrate type and quality can play on dislocation type and density.

Keywords

electronic materialtransmission electron microscopy (TEM)metalorganic deposition
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1068: Symposium C – Advances in GaN, GaAs, SiC and Related Alloys on Silicon Substrates , 2008 , 1068-C06-03
Copyright
Copyright © Materials Research Society 2008

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References

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