Rapid Melt Growth of Germanium Crystals with Self-Aligned Microcrucibles on Si Substrates

A rapid melt growth method was developed to produce Ge crystals including Ge pillars, nanowires, and Ge-on-insulator. Amorphous Ge was deposited and patterned, then crystallized by melting and solidifying using Si substrates for seeding. Self-aligned microcrucibles were used to contain the Ge liquid during the crystallization anneal. The misfit defects were terminated within small regions around the seeding windows by a necking mechanism. Crystallization calculations showed that very high epitaxial growth velocity can be achieved when the temperature of Ge liquid is lower than but close to its melting point, while the random unseeded nucleation rate is very low in the same temperature range. High-quality Ge nanowires and Ge-on-insulator structures are produced with a simple and robust process. The rapid melt growth technique works very well with a variety of film thickness, including that of nanometer ultrathin structures. The surface smoothness obtained by Ge deposition is retained during crystallization and the film thickness is also controlled by deposition.