Investigation of silicon-germanium nanowires THz emission

Semiconductor nanowires and nanostructures have a great potential for Terahertz generation and detection, especially because certain materials properties such as optical absorption, high electron and hole mobility, and short carrier lifetime can be engineered through structural changes and material compositions. In such structures, the variation in geometry and surface charge characteristics can greatly influence the dynamics of photoexcited carrier recombination, which is directly related to strength of the Terahertz emission. Compared to thin films, nanowires dramatically increase the effective surface area which would have an important role in the absorption. In this work, we studied theoretical and experimental investigation of carrier lifetime reduction and the properties of THz generation in SiGe nanowires. Terahertz emission spectroscopy was used to generate THz pulses from the nanowire samples. Then standard Terahertz time-domain spectroscopy measurements were carried to investigate the material properties and high frequency carrier dynamics of Si_1-xGe_x nanowires. A mobility of 1615 cm²/Vs and a carrier lifetime of ~0.24 ps were measured. The influence of carrier dynamics properties on the THz generation from SiGe nanowires was investigated in details.