Formation of Large-Grain Ge(111) Films on Insulator by Gold-Induced Layer-Exchange Crystallization at Low Temperature

A formation technique of orientation-controlled large-grain (< 10 mu m) Ge crystals on insulator at low temperature (<= 350 degrees C) has been investigated to realize advanced flexible electronics. Previously, we proposed a gold-induced crystallization technique, and demonstrated low temperature crystallization (250 degrees C) of Ge on insulator. In the present study, we intentionally inserted thin Al2O3 layers between gold and a-Ge layer, to control crystal nucleation. Consequently, (111)-oriented large-grain (< 20 mu m) Ge crystals are obtained at 350 degrees C by optimizing interfacial oxide layer thickness. It is speculated that this phenomena is attributed to suppression of random bulk nucleation of Ge in Au films and resultant dominance of interfacial nucleation at Ge/SiO2 interfaces.