Comparison of near-infrared absorption and photoresponse of silicon doped with Se and Te via fs-laser irradiation

We compare the surface morphology, optical properties and infrared photoresponse of Se- and Te-doped silicon prepared by femtosecond-laser irradiation of Si coated with dopant thin films. Both the two samples show similar column structures and strong sub-band gap light absorption. Annealing the doped silicon leads to attenuation of the sub-band gap absorption. However, the attenuation degree of the Se-doped silicon is greater in comparison with that of Te-doped silicon. To explain the cause of the difference in the attenuation, we fit the attenuation of experimental absorption coefficient using an equation. Thermal activation energy and pre-exponential factor in the equation are considered to be associated with metastability of chalcogen-Si bonds and dopant diffusivity, respectively. We extract the thermal activation energy and pre-exponential factor of Se- and Te-doped silicon from the fitted data, and the results suggest that it is different dopant diffusivity instead of different chalcogens-Si bond energy causes difference in the attenuation. Furthermore, Te-doped silicon photodiode exhibits higher photocurrent response, which makes it possible to be more valuable candidate for fabricating Si-based photoelectric detector.