Growth and characterization of Si_1-xGe_tx QDs on Si/Si_0.8Ge_0.2 layer

Si_1-xGe_tx QDs structures were grown onto Si/Si_{0. 8}Ge_{0. 2} layer using RPCVD system. Ge composition in Si_1-xGe_tx QDs was determined as about 30% and 40%. Three peaks are observed in Raman spectrum, which are located at about 520, 410, and 295 cm^-1, corresponding to the vibration of Si-Si, Si-Ge, and Ge-Ge phonons, respectively, and the Si_1-xGe_tx QDs related peak was located at 490 cm^-1. The PL spectrum that originates from the radiative recombinations came from the Si substrate, the Si_{0. 8}Ge_{0. 2} layer and Si_1-xGe_tx QDs. For Si_1-xGe_tx QDs, the transition peaks related to the QDs region observed in the photocurrent spectrum were preliminarily assigned to electron-heavy hole (e-hh) and electron-light hole (e-lh) fundamental excitonic transitions.