Enhanced crystal nucleation in a-Si on SiO 2 by local Ge doping

Abstract

The effects of local Ge doping on the crystal nucleation in the solid-phase crystallization (SPC) of a-Si films on SiO 2 films were investigated. Three types of sample structures, (a) a-Si/a-Ge/a-Si/SiO 2, (b) a-Si/a-Ge/SiO 2, and (c) SiO 2/a-Ge/a-Si/SiO 2, were prepared and annealed at 600 °C. For the structure (a) with a thin (∼5 nm) Ge film, Ge atoms completely diffused into a-Si films, and SPC was not enhanced. On the other hand, for the structure (a) with Ge films thicker than 10 nm, Ge atoms were localized at the initial position. Such abnormal retardation of Ge diffusion was remarkable for the structures (b) and (c) even for samples with thin Ge films. For samples with Ge localization, significant enhancement of SPC of a-Si was observed. These results indicated that crystal nucleation was initiated in the localized Ge films, and then propagated into a-Si films. The local Ge doping at a-Si/SiO 2 interfaces can be employed to selectively induce the nucleation at the interfaces.