Abstract
Low-temperature (≤300°C) formation of orientation-controlled large-grain (≥10μm) Ge-rich (≥50%) SiGe crystals on insulator are realized by the gold-induced layer-exchange technique. Stacked structures of a-Si1−xGex (0≤x≤1)/Au/SiO2 are employed as starting materials. Here, thin-Al2O3 layers are introduced as diffusion barrier at a-SiGe/Au interfaces to suppress random bulk-nucleation and make (111)-oriented interface-nucleation on SiO2 dominant. For samples with Ge fraction of 80%–100%, (111)-oriented large-grains (≥10μm) are obtained through layer-exchange during annealing at 250°C. On the other hand, layer-exchange for Ge fraction of 50% does not proceed at 250°C. This phenomenon is attributed to retardation of lateral growth by introduction of Si. To enhance lateral growth, increase of annealing temperature is examined. As a result, (111)-oriented large-grains (≥10μm) are realized for SiGe with Ge fraction of 50%–100%, having uniform composition profiles, by annealing at 300°C. This technique is very useful to realize high-performance flexible electronics, employing plastic substrates (softening temperature: ~350°C).
Published Version
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