Electronic transport characterization of silicon wafers by laterally resolved free-carrier absorption and multiparameter fitting

Laterally resolved modulated free-carrier absorption (MFCA) is applied to the simultaneous determination of the electronic transport properties of semiconductor wafers. A rigorous three-dimensional carrier diffusion model is used to fit the observed dependences of the MFCA signal amplitude and phase on the separation between the pump and probe laser spots, measured at several modulation frequencies covering an appropriate range. This leads to a simultaneous and unambiguous determination of the values of three transport parameters, namely, the minority-carrier lifetime tau, the carrier diffusivity D, and the front surface recombination velocity s(1). The extracted values for a n-type Si wafer with a resistivity of 7-10 Omega cm are 53 mu s (tau), 16.6 cm(2)/s (D), and < 200 cm/s (s(1)), respectively. (c) 2006 American Institute of Physics.