Correlation between biaxial stress and free exciton transition in AlN epilayers

B. N. Pantha, N. Nepal, T. M. Al Tahtamouni, M. L. Nakarmi, J. Li, J. Y. Lin, H. X. Jiang

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Abstract

Photoluminescence (PL) spectroscopy and x-ray diffraction measurements were employed to study biaxial strain in AlN epilayers grown on different substrates. X-ray diffraction revealed that AlN epilayers grown on AlN bulk substrates (or homoepilayers) have the same lattice parameters as AlN bulk crystals and are almost strain-free. Compared to the free exciton (FX) transition in an AlN homoepilayer, the FX line was 31 meV higher in AlN/sapphire due to a compressive strain and 55 (69) meV lower in AlNSiC (AlNSi) due to a tensile strain. A linear relationship between the FX transition energy peak position and in-plane stress was obtained, and a value of 45 meVGPa for the linear coefficient of the stress-induced bandgap shift in AlN epilayers was deduced. The work here establishes PL as another simple and effective method for monitoring the biaxial stress in AlN epilayers.

Original languageEnglish
Article number121117
JournalApplied Physics Letters
Volume91
Issue number12
DOIs
StatePublished - 2007

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