Quantum-confined direct band transitions in tensile strained Ge/SiGe quantum wells on silicon substrates.

We directly demonstrate quantum-confined direct band transitions in the tensile strained Ge/SiGe multiple quantum wells grown on silicon substrates by room temperature photoluminescence. The tensile strained Ge/SiGe multiple quantum wells with various thicknesses of Ge well layers are grown on silicon substrates with a low temperature Ge buffer layer by ultrahigh vacuum chemical vapor deposition. The strain status, crystallographic, and surface morphology are systematically characterized by high-resolution transmission electron microscopy, atomic force microscopy, x-ray diffraction, and Raman spectroscopy.