Elastic and Plastic Stress Relaxation in Highly Mismatched SiGe/Si Crystals
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Elastic and Plastic Stress Relaxation in Highly Mismatched SiGe/Si Crystals Fabio Isa1,2, Arik Jung1,2, Marco Salvalaglio3, Yadira Arroyo Rojas Dasilva2, Mojmír Meduňa4,5, Michael Barget3, Thomas Kreiliger1, Giovanni Isella6, Rolf Erni2, Fabio Pezzoli3, Emiliano Bonera3, Philippe Niedermann7, Kai Zweiacker8, Antonia Neels8, Alex Dommann8, Pierangelo Gröning9, Francesco Montalenti3 and Hans von Känel1,2 1
Laboratory for Solid State Physics, ETH Zürich, Otto-Stern-Weg 1, Zürich, CH-8093, Switzerland 2 Electron Microscopy Center, Empa, Überlandstrasse 129, Dübendorf, CH-8600, Switzerland 3 L-NESS and Department of Materials Science, Università di Milano-Bicocca, Via Cozzi 55, Milano, I-20125, Italy 4 Department of Condensed Matter Physics, Masaryk University, Kotlářská 2, Brno, 61137, Czech Republic 5 CEITEC, Masaryk University, Kamenice 5, Brno, 60177, Czech Republic 6 L-NESS and Department of Physics, Politecnico di Milano, Via Anzani 42, Como, I-22100, Italy 7 CSEM, Rue Jaquet-Droz 1, Neuchâtel, CH-2002, Switzerland 8 Center for X-Ray Analytics, Empa, Überlandstrasse 129, Dübendorf, CH-8600, Switzerland 9 Advanced Materials and Surfaces Department, Empa, Überlandstrasse 129, Dübendorf, CH8600, Switzerland ABSTRACT We present a new concept applicable to the epitaxial growth of dislocation-free semiconductor structures on a mismatched substrate with a thickness far exceeding the conventional critical thickness for plastic strain relaxation. This innovative concept is based on the out-of-equilibrium growth of compositionally graded alloys on deeply patterned substrates. We obtain space-filling arrays of individual crystals several micrometers wide in which the mechanism of strain relaxation is fundamentally changed from plastic to elastic. The complete absence of dislocations at and near the heterointerface may pave the way to realize CMOS integrated SiGe X-ray detectors. INTRODUCTION The epitaxial growth of semiconductors which differ in lattice and thermal expansion coefficients suffers from hard to solve problems such as misfit and threading dislocation formation and wafer bowing. Dislocations are detrimental to the electro-optical properties of devices [1] and large wafer bowing hampers device processing. Several approaches have been proposed to solve these problems. Threading dislocations may be drastically reduced or even eliminated by growing planar compositionally graded alloys [2], by employing patterned substrates for aspect ratio trapping [3], epitaxial lateral overgrowth [4] or 3D heteroepitaxy [5]. By means of the latter also the thermal mismatch could be successfully relaxed. Misfit dislocations are even harder to come by as coherent, thick, highly mismatched heterostructures may be realized only if the epitaxial material is deposited on mesa structures sized in the tens of
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