Low Density Carrier Mobility in Silicon and Gallium Arsenide by Two-Photon Time-Resolved Terahertz Spectroscopy

Below bandgap two-photon excitation of bulk silicon and gallium arsenide samples is used to evenly generate low density carriers (<;10
¹³
cm
^-3
) throughout the entire sample thickness. Analysis of the frequency-dependent THz conductivity as a function of density allows determination of mobility at lower densities than previously examined using Hall contact measurements.