A low-temperature (≤300°C) growth technique of quasi-single crystal, i.e., orientation-controlled large-grain (≥10 μm), Ge-related semiconductors, on insulator is desired for realization of advanced flexible electronics. To achieve this, we have developed the gold-induced layer-exchange crystallization technique using a-SiGe/Au stacked structures. By introduction of a diffusion barrier with appropriate thickness into the a-SiGe/Au interface, (111)-oriented quasi-single crystal SiGe is achieved on insulating substrates at low temperatures (∼300°C). Based on these results, this technique is developed to form quasi-single crystal Ge on flexible plastic sheets. The grown layers have high carrier mobility, because residual Au hardly deteriorates the electrical properties of grown layers due to the low solubility of Au in Ge. This technique will facilitate the realization of advanced flexible electronics.