Low-temperature FTIR Investigation of Aluminum Doped Solar-grade Silicon

Low-temperature FTIR spectroscopy is further developed to be applicable to measure the aluminum concentration in solar-grade silicon in concentrations up to 4 × 1016 atoms/cm3. Absorption spectra of multicrystalline silicon samples doped with varying aluminum content are measured at 10 K and correlated to the dopant density obtained by four point probe resistivity measurements. Calibration factors for absorption peaks of unpaired substitutional aluminum at 443, 472, 516+524 and 867 cm-1 as well as for a Fano anti-resonance at 962 cm-1 are reported.