Photothermal subgap spectra of doped silicon wafers

Abstract Subgap absorption spectra of doped silicon wafers are determined. The spectra are characterized through the values of the exponential tail and optical gap. The free carrier contribution is also evidenced and good agreement with theory is shown at high dopant concentrations. In lightly doped samples, a non-negligible contribution to the absorption is attributed to optically active defects. The difference between optically and electrically active defects is assumed to be due to different kinds of impurities.