Low-temperature (≤ 300 °C) formation of orientation-controlled large-grain (≥ 10 μm) Ge-rich SiGe on insulator by gold-induced crystallization

• Gold-induced crystallization is developed to Ge-rich SiGe on insulator.
• Layer-exchange crystallization proceeds at low temperatures (≤ 300 °C).
• (111)-oriented large-grain (≥ 10 μm) SiGe is realized for Ge fraction of 50%–100%.

Low-temperature (≤ 300 °C) formation of orientation-controlled large-grain (≥ 10 μm) 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 (≥ 10 μm) 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 (≥ 10 μm) 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).