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Computational Analysis of Low-Energy Dislocation Configurations in Graded Layers

Materials Science Department, University of Milano-Bicocca, Via R. Cozzi 55, I-20125 Milano, Italy
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Crystals 2020, 10(8), 661; https://doi.org/10.3390/cryst10080661
Received: 26 May 2020 / Revised: 21 July 2020 / Accepted: 23 July 2020 / Published: 1 August 2020
Graded layers are widely exploited in semiconductor epitaxy as they typically display lower threading dislocation density with respect to constant-composition layers. However, strain relaxation occurs via a rather complex distribution of misfit dislocations. Here we exploit a suitable computational approach to investigate dislocation distributions minimizing the elastic energy in overcritical constant-composition and graded layers. Predictions are made for SiGe/Si systems, but the methodology, based on the exact (albeit in two dimensions and within linear elasticity theory) solution of the stress field associated with a periodic distribution of defects, is general. Results are critically compared with experiments, when possible, and with a previous mean-field model. A progressive transition from one-dimensional to two-dimensional distributions of defects when continuous linear grading is approached is clearly observed. Interestingly, analysis of the low-energy distribution of dislocations reveals close analogies with typical pile-ups as produced by dislocation multiplication. View Full-Text
Keywords: dislocation; heteroepitaxy; modeling; SiGe dislocation; heteroepitaxy; modeling; SiGe
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Lanzoni, D.; Rovaris, F.; Montalenti, F. Computational Analysis of Low-Energy Dislocation Configurations in Graded Layers. Crystals 2020, 10, 661.

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