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 - Jul 11 2008

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ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)

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