Formation of large grain Ge single crystal on insulating substrate by liquid-solid coexisting annealing of a-Ge(Sn)

To realize next generation thin-film-transistors (TFTs), seedless rapidmelting growth of Ge on insulator is investigated. By rapid-thermal annealing (RTA) of amorphous GeSn (a-GeSn) layers on insulating substrates at a temperature between the solidification point and the melting point, GeSn layers melt incompletely, which generates a limited number of solid nuclei as residue. Once cooling starts, liquid-phase epitaxial growth occurs from these nuclei, which results in growth of large-grain crystals. Since segregation coefficient of Sn in Ge is very small (∼0.02), almost all Sn atoms segregate at edges of the grown regions. As a result, almost Snfree (≤1%) large Ge crystal grains are achieved on insulating substrates by a self-organizing process.