Nucleation control in solid-phase crystallization of a-Si/SiO2 by local Ge insertion

The effects of local Ge insertion on the solid-phase crystallization (SPC) of a-Si films have been investigated. Three types of stacked structures. i.e., (a) a-Si/a-Ge/a-Si/SiO2, (b) a-Si/a-Ge/SiO2, and (c) SiO2/a-Ge/a-Si/SiO2, were annealed at 600degreesC. For structure (a) with thin (similar to5 nm) Ge films, Ge atoms completely diffused into both sides of a-Si regions, and SPC was not enhanced. However. when Ge thickness was increased to more than 10 nm, Ge atoms were localized. Such localization became significant for structures (b) and (c) even for samples with thin Ge films. In addition, significant enhancement of SPC of a-Si was observed. These results indicated that crystal nucleation was initiated in Ge layers, and then propagated into a-Si layers. Therefore. interface-nucleation-driven SPC becomes possible using Structures (b) and (c). This will be a useful tool in achieving oriented Si growth on SiO2.