Anti-relaxation of tensile lattice strain in Si-embedded Ge strip structure for photonic device applications

This paper reports an anti-relaxation of tensile lattice strain in a narrow Ge strip epitaxially grown on Si by CVD. In an ordinary Ge mesa strip as narrow as 1 μ m or below, an in-plane tensile strain as high as 0.2% due to the thermal expansion mismatch with the Si substrate is relaxed by edge-induced relaxation. Such a relaxation is significantly prevented by embedding the Ge strip entirely in Si, as supported by Raman and photoluminescence spectra as well as theoretical strain analysis. This anti-relaxation is effective for efficient optical absorption and light emission at around 1.55 μ m.