Optical property of Si_0.8Ge_0.2/Si multi- layer grown by using RPCVD

We have investigated the characterization of Si_0.8Ge _0.2/Si multi-layer grown directly onto Si (001) substrates using reduced pressure chemical vapor deposition (RPCVD). The structural properties of the Si_0.8Ge_0.2/Si multi-layer were investigated using X-ray diffraction (XRD) and TEM. Three peaks are observed in Raman spectrum, which are located at about 514, 404, and 303cm^-1, corresponding to the vibration of Si-Si, Si-Ge, and Ge-Ge phonons, respectively. The PL spectrum originates from the radiative recombinations both from the Si substrate and the Si_0.8Ge_0.2/Si multi-layer. For Si_0.8Ge _0.2/Si multi-layer, the transition peaks related to the QW region observed in the photocurrent spectrum were preliminarily assigned to electron-heavy hole (e-hh) and electron-light hole (e-lh) fundamental excitonic transitions.