Characterization of doped silicon in low carrier density region by terahertz frequency Faraday effect

We report on optical characterization of doped semiconductors by using terahertz Faraday rotation measurements in Cross-Nicole configuration. The detection sensitivity of Faraday rotation angle as small as 0.5mrad is obtained. The scheme is applied to an n-type silicon wafer of 525μm thickness in carrier freeze-out temperature region. The carrier density below N=1×1014cm−3 is evaluated under magnetic field B=1T.