Growth of Smooth, Low-Defect Germanium Layers on (111) Silicon via an Intermediate Islanding Process

Epitaxial growth of thick Ge layers on a (111)-Si substrate has been investigated. We demonstrate that the residual compressive strain in a thin, partially relaxed Ge seed layer can be exploited to promote an intermediate islanding step, significantly reducing the threading dislocation density (similar to 3 x 10(8) cm(-2)) and almost entirely suppressing stacking fault formation. The higher Ge growth rate on the {113} sidewalls of the islands compared to the (111) top surface results in a smooth layer with a low rms surface roughness of 2 nm. Such layers have the potential to be extremely important in realizing next-generation high-mobility n-channel transistors. (c) 2012 The Japan Society of Applied Physics