Trench-filling heteroepitaxy of [100]-oriented germanium arrays on (001) silicon substrate

Abstract

Trench-filling heteroepitaxy of germanium (Ge) on (001) silicon (Si) substrate is studied toward normal-incidence/free-space NIR photodetectors, where micron-thick Ge is prepared with a large surface coverage and in a growth time as short as possible. Arrayed trenches as deep as 1 μm are patterned on (001) Si in the [100] direction, intentionally deviating from the ordinary [110] direction. The molecular flux regime of CVD induces a substantial lateral growth of Ge at the trench sidewalls of the {010} planes, crystallographically identical to the (001) plane at the trench bottom. Despite the Ge thickness of 0.5 μm on an unpatterned surface, the 0.6 μm wide arrayed trenches of 1.0 μm in depth are successfully filled with Ge, although the filling is suppressed when increasing the trench width. The inter-trench Si fin width is also an important parameter concerning not only the surface coverage but also the structural degradation during the growth.