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Improved Heteroepitaxial MBE GaN Growth with a Ga Metal Buffer Layer

Published online by Cambridge University Press:  15 March 2011

Yihwan Kim ,
Sudhir G. Subramanya ,
Joachim Krueger ,
Henrik Siegle ,
Noad Shapiro ,
Robert Armitage ,
Henning Feick ,
Eicke R. Weber ,
Christian Kisielowski  and
Yi Yang
...Show all authors
Yihwan Kim
Affiliation:
Department of Materials Science and Engineering, University of California at Berkeley, and Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, U.S.A.
Sudhir G. Subramanya
Affiliation:
Department of Materials Science and Engineering, University of California at Berkeley, and Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, U.S.A.
Joachim Krueger
Affiliation:
Department of Materials Science and Engineering, University of California at Berkeley, and Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, U.S.A.
Henrik Siegle
Affiliation:
Department of Materials Science and Engineering, University of California at Berkeley, and Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, U.S.A.
Noad Shapiro
Affiliation:
Department of Materials Science and Engineering, University of California at Berkeley, and Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, U.S.A.
Robert Armitage
Affiliation:
Department of Materials Science and Engineering, University of California at Berkeley, and Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, U.S.A.
Henning Feick
Affiliation:
Department of Materials Science and Engineering, University of California at Berkeley, and Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, U.S.A.
Eicke R. Weber
Affiliation:
Department of Materials Science and Engineering, University of California at Berkeley, and Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, U.S.A.
Christian Kisielowski
Affiliation:
National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, U.S.A.
Yi Yang
Affiliation:
Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, WI 53706, U.S.A.
Franco Cerrina
Affiliation:
Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, WI 53706, U.S.A.
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Abstract

We demonstrate that the use of pure gallium (Ga) as a buffer layer results in improved crystal quality of GaN epilayers grown by plasma-assisted molecular beam epitaxy on c-plane sapphire. The resulting epilayers show electron Hall mobilities as high as 400 cm2/Vs at a background carrier concentration of 4 × 1017 cm−3, an outstanding value for an MBE-grown GaN layer on sapphire. Structural properties are also improved; the asymmetric (101) X-ray rocking curve width is drastically reduced with respect to that of the reference GaN epilayer grown on a low-temperature GaN buffer layer. Nitrided Ga metal layers were investigated for different Ga deposition time. These layers can be regarded as templates for the subsequent Ga main layer growth. It was found that there is an optimum Ga metal layer deposition time for improving the electron mobility in the epilayer. Heating of the Ga metal layer to the epilayer growth temperature under nitrogen plasma is found to be sufficient to produce highly oriented GaN crystals. However, nonuniform surface morphology and incomplete surface coverage were observed after nitridation of comparatively thick Ga metal layers. This is shown to be the reason for the decreasing electron mobility of the epilayers as the Ga metal layer thickness exceeds the optimum value.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 622: Symposium T – Wide-Bandgap Electronic Devices , 2000 , T4.10.1
Copyright
Copyright © Materials Research Society 2000

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References

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