Zone-melt epitaxial crystallization of Ge on oxide-coated or nitride-coated Si.

Thin films of Ge have been laterally crystallized on oxidized or nitride Si using a molten-zone recrystallization technique. An argon ion laser and a graphite strip-heater were used as energy beams. The insulating layers were patterned into islands to allow either seeded or unseeded crystallization. Moderately twinned single crystals up to 500microns x 400microns have been obtained. No obvious defects were observed for crystals up to 160microns x 80microns. Thin (300-500angstroms) tungsten capping layers were necessary to help Ge crystallize with stability. The Ge morphology also improved with tungsten capping. Without capping, Ge displayed extensive dendritic morphology. In general, Ge-on- insulator (GOI) behaves quite differently from Si-on-insulator (SOI). Si generates an extensive sub-boundary network; Ge generates extensive areas of twinned or faceted crystals mixed with sub-boundary-like features. Cross-sectional TEM, X-ray, etching, and morphological characterization results are discussed.