Thermal-annealing dependence of C-related atomic configuration in Si_(1-x-y)Ge_(x)C_(y) crystals grown by ultra-high-vacuum chemical-vapor deposition

摘要

Si_(1-x-y)Ge_(x)C_(y) crystals were grown by ultra-high-vacuum chemical-vapor deposition and their thermal-annealing behaviors were studied by infrared (IR) absorption measurements. The present samples exhibited absorption peaks originating from local vibrational modes of substitutional C atoms with two different atomic configurations; one is a C atom with four Si neighbors (Si_(4) configuration) and the other is with one Ge and three Si neighbors (Si_(3)Ge_(1) configuration). As the annealing temperature was increased from 700 to 950℃, the absorption peak of the C atoms with Si_(3)Ge_(1) configuration increased in intensity. This clearly demonstrated that thermal annealing leads to the formation of Ge-C bonds. Moreover, the composition dependence of the IR spectra suggested that Ge-C bonds are formed to reduce the strain energy of the Si_(1-x-y)Ge_(x)C_(y) crystals.