Stress evolution during the early stages of AlN vapor growth

B. Wu, J. Bai, V. L. Tassev, M. Lal Nakarmi, W. Sun, X. Huang, M. Dudley, H. Zhang, D. F. Bliss, J. Lin, H. Jiang, J. Yang, M. Asif Khan

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

5 Scopus citations


The evolution of stress during the MOCVD growth of AlN thin films on sapphire substrates under both low and high temperature conditions has been evaluated. The final stress state of the films is assumed to consist of the summation of stresses from three different sources: (1) the stress which arises from residual lattice mismatch between film and substrate i.e. that which persists after partial relaxation by misfit dislocation formation. The extent of relaxation is determined from High Resolution TEM analysis of the substrate/film interface; (2) the stress arising from the coalescence of the 3D islands nucleated in this high mismatch epitaxy process. This requires knowledge of the island sizes just prior to coalescence and this was provided by AFM studies of samples grown under the conditions of interest; and (3) the stress generated during post-growth cooling which arises from the differences in thermal expansion coefficient between AlN and sapphire. The final resultant stress, comprising the summation of stresses arising from these three sources, is found to be tensile in the sample grown at lower temperature and compressive in the sample grown at higher temperature. These results are in general qualitative agreement with results of TEM and High resolution X-ray diffraction (HRXRD) studies, which show evidence for tensile and compressive stresses in the low temperature and high temperature cases, respectively.

Original languageEnglish
Title of host publicationMaterials Research Society Symposium Proceedings
Number of pages6
StatePublished - 2006
Event2005 Materials Research Society Fall Meeting - Boston, MA, United States
Duration: Nov 28 2005Dec 2 2005

Publication series

NameMaterials Research Society Symposium Proceedings
ISSN (Print)0272-9172


Conference2005 Materials Research Society Fall Meeting
Country/TerritoryUnited States
CityBoston, MA


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