Control of Defects in Aluminum Gallium Nitride ((Al)GaN) Films on Grown Aluminum Nitride (AlN) Substrates

Report No. ARL-TR-6350
Authors: Iskander G. Batyrev, Chi-Chin Wu, Peter W. Chung, N. Scott Weingarten and Kenneth A. Jones
Date/Pages: February 2013; 46 pages
Abstract: We present efforts aimed at establishing a multiscale approach for simulating dislocations in aluminum gallium nitride ((Al)GaN) semiconductors. We performed quantum mechanical and classical molecular dynamics (MD) simulations to study the electronic and atomic structure of threading edge and screw dislocations in AlGaN, focusing on the structure of the dislocation core and the electrical activity of dislocations, and estimating dislocation velocities as a function of applied stress and temperature. We used the calculated mobility functions from MD to study different junction configurations using a discrete dislocation dynamics (DDD) simulator, ParaDiS. Finally, we predicted the most likely slip planes in wurtzite (Al)GaN semiconductors based on general crystallographic principles. The most important results are (1) aluminum (Al) atoms do not segregate to the dislocation core and atoms in the dislocation core do not produce any defect levels in the bandgap; (2) we performed first time classical MD calculations of dislocation velocity as a function of applied stress for three slip systems in gallium nitride (GaN); (3) we adapted ParaDiS to simulate wurtzite semiconductors; and (4) the plane strain produced by the lattice mismatch during growth on the (0001) plane does not create a shear stress on the basal or prismatic planes, hence the operational slip plane must be a pyramidal plane, the most probable being the 1/3(1123){1122} slip system.
Distribution: Approved for public release
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Last Update / Reviewed: February 1, 2013