Abstract

Al0.4 Ga0.6 N layers grown by molecular beam epitaxy on (0001) AlN/sapphire composite substrates were examined using transmission electron microscopy. The layers show modulated structures consisting of Al-rich and Ga-rich regions. 1:1 atomic ordering on the (0001) planes was not observed. To rationalize the formation of modulations, we invoke the presence of phase separation induced Al-rich and Ga-rich regions at the AlGaN/composite interface, the development of surface undulations due to the presence of two-dimensional stresses between these regions and asymmetry in the wetting characteristics of the Al-rich and Ga-rich regions. Arguments are also developed to explain the absence of 1:1 ordering in these layers.

Original languageEnglish (US)
Article number261914
JournalApplied Physics Letters
Volume92
Issue number26
DOIs
StatePublished - 2008

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molecular beam epitaxy
modulation
composite materials
wetting
sapphire
asymmetry
transmission electron microscopy

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)

Cite this

Composition modulations in Al0.4 Ga0.6 N layers grown by molecular beam epitaxy. / Wise, A.; Nandivada, R.; Strawbridge, B.; Carpenter, Ray; Newman, Nathan; Mahajan, S.

In: Applied Physics Letters, Vol. 92, No. 26, 261914, 2008.

Research output: Contribution to journalArticle

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abstract = "Al0.4 Ga0.6 N layers grown by molecular beam epitaxy on (0001) AlN/sapphire composite substrates were examined using transmission electron microscopy. The layers show modulated structures consisting of Al-rich and Ga-rich regions. 1:1 atomic ordering on the (0001) planes was not observed. To rationalize the formation of modulations, we invoke the presence of phase separation induced Al-rich and Ga-rich regions at the AlGaN/composite interface, the development of surface undulations due to the presence of two-dimensional stresses between these regions and asymmetry in the wetting characteristics of the Al-rich and Ga-rich regions. Arguments are also developed to explain the absence of 1:1 ordering in these layers.",
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AU - Wise, A.

AU - Nandivada, R.

AU - Strawbridge, B.

AU - Carpenter, Ray

AU - Newman, Nathan

AU - Mahajan, S.

PY - 2008

Y1 - 2008

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AB - Al0.4 Ga0.6 N layers grown by molecular beam epitaxy on (0001) AlN/sapphire composite substrates were examined using transmission electron microscopy. The layers show modulated structures consisting of Al-rich and Ga-rich regions. 1:1 atomic ordering on the (0001) planes was not observed. To rationalize the formation of modulations, we invoke the presence of phase separation induced Al-rich and Ga-rich regions at the AlGaN/composite interface, the development of surface undulations due to the presence of two-dimensional stresses between these regions and asymmetry in the wetting characteristics of the Al-rich and Ga-rich regions. Arguments are also developed to explain the absence of 1:1 ordering in these layers.

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