Optical properties of Si_1-xGe_x quantum dots grown using RPCVD

The optical properties of Si_1-xGe_x quantum dots (QDs) grown directly onto Si (001) substrates without a buffer layer using the reduced pressure chemical vapor deposition (RPCVD) system have been investigated. From the results of the EDX and XRD analyses of the Si_1-xGe_x QD structures, the Ge composition in the Si_1-xGe_x QDs was determined to be approximately 30% and 40%, for the respective analyses, and the values of the residual strain e{open} of the Si_0.7Ge_0.3 and Si_0.7Ge_0.4 samples were calculated as -0.0095 and -0.0089, respectively. Five peaks were observed in the Raman spectra, which correspond to the vibration of Si-Si, Si-Ge, and Ge-Ge phonons, and the Si_1-xGe_x QD related peaks were located at 486 cm^-1 and 490 cm^-1. The transition peaks related to the QD region observed in the photocurrent spectrum were preliminarily assigned to the electron-heavy hole (e-hh) and electron-light hole (e-lh) transitions. The no-phonon (NP) peak of Si_1-xGe_x QDs was clearly observed in PL spectrum.