Temperature And Carrier-Density Dependence Of Electron-Hole Scattering In Silicon Investigated By Optical-Pump Terahertz-Probe Spectroscopy

We measured the optical conductivity sigma(omega) spectra of photodoped silicon by optical-pump terahertz-probe spectroscopy and analyzed them with a two-carrier Drude model. Taking into account the values of electron (hole)-phonon scattering rates previously reported in chemically doped silicon, we evaluated the electron-hole scattering rates gamma(e-h). From 293 to 90 K, the magnitudes and temperature dependence of gamma(e-h) were successfully reproduced by a theoretical model including the effects of Rutherford scattering, Coulomb screening, and Pauli exclusion. This suggests that these three factors dominate electron-hole scattering processes in silicon. Below 90 K, gamma(e-h) becomes larger than that of the theoretical curve, which is attributable to a prolongation of the relaxation time of hot carriers.