Thermal-mechanical modeling of single crystal AlN and GaN

Karvanirabori, Payman
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Maniatty, Antoinette M.
Picu, Catalin R.
Samuel, Johnson
Dutta, Partha S.
Bondokov, Robert
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Mechanical engineering
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This electronic version is a licensed copy owned by Rensselaer Polytechnic Institute, Troy, NY. Copyright of original work retained by author.
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In this work, thermal-mechanical models are being developed, based on underlying micromechanical behavior of III-nitride single crystals at growth temperatures, for use in process design. A crystal plasticity model that is capable of capturing the underlying mechanisms of dislocation motion, multiplication, and interactions in wurtzite structure (hexagonal) crystals is defined to accurately model the elastic-plastic behavior of GaN and AlN crystals at elevated temperatures. The model for AlN is extended from relations developed for GaN based on available experimental data. Algorithms for integrating the constitutive model and computing the consistent tangent modulus are formulated, and the material model is implemented into a crystal plasticity finite element framework. Finite element models of crystal growth for different processing conditions are simulated. The simulation predicts cracking and dislocation defect density in order to improve the yield and reduce the manufacturing cost of high quality III-nitride semiconductors. Furthermore, the resulting simulation capability can be used in conjunction with relevant experiments to backout key thermal-mechanical material properties at high temperatures.
August 2014
School of Engineering
Dept. of Mechanical, Aerospace, and Nuclear Engineering
Rensselaer Polytechnic Institute, Troy, NY
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