Carrier-density-wave transport property depth profilometry using spectroscopic photothermal radiometry of silicon wafers II: Experimental and computational aspects

The experimental verification of a previously presented theoretical model for the photothermal radiometric (PTR) signal from an Si wafer excited by a laser of arbitrary wavelength is presented. A multiparameter fitting algorithm is developed and is used to fit experimental frequency scans to the theoretical model. The recombination lifetime and surface recombination velocity values extracted from the fits are consistent for all of the experiments performed. The diffusion coefficients for the more strongly absorbed excitation wavelengths are greater than those measured when using deeper penetrating excitation wavelengths. This discrepancy is discussed in terms of the dependence of the PTR signal on injected carrier densities and the nonlinearity of the PTR signal with temperature. The sensitivity of the PTR signal to a localized defect is shown to increase with the proximity of the defect to the centroid of the injected carrier density. The method amounts to carrier-density-wave depth profilometry of the relevant electronic transport parameters.