With Fourier-transform photocurrent spectroscopy and spectral response measurements, we show that silicon doped with sulfur by femtosecond laser irradiation generates excess carriers, when illuminated with infrared light above 1100 nm. Three distinct sub-bandgap photocurrent features are observed. Their onset energies are in good agreement with the known sulfur levels S +, S0, and S2 0. The excess carriers are separated by a pn-junction to form a significant photocurrent. Therefore, this material likely demonstrates the impurity band photovoltaic effect

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In this letter, we demonstrate that silicon can be doped with electrically active sulfur donors beyond the solubility limit of 3 × 10(exp 16) cm-3. We investigate the sulfur doping profile at the surface of femtosecond-laser processed silicon with secondary ion mass spectroscopy (SIMS) and capacitance-voltage measurements. SIMS confirms previous observations that the fs-laser process can lead to a sulfur hyperdoping of 5 × 10(exp 19) cm-3 at the surface. Nevertheless, the electrical measurements show that less than 1% of the sulfur is electrically active as a donor

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We propose a method to obtain accurate capacitance-voltage (C-V) curves in the presence of multiple space charges. This method uses impedance spectroscopy to evaluate individual space charges separately. The advantage is that the knowledge of the exact equivalent circuit is not essentially needed. The comparison with other methods to calculate the doping concentration NA shows that our method is unaffected by series resistances and agrees best with the correct value of NA. The evaluation of the impedance spectra leads to a more thorough understanding of the respective Mott-Schottky plots.