The effects of a thin film dopant precursor on the structure and properties of femtosecond-laser irradiated silicon

Femtosecond (fs) laser irradiation of a silicon substrate coated with a thin film is a flexible approach to producing metastable alloys with unique properties, including near-unity sub-band gap absorptance extending into the infrared. However, dopant incorporation from a thin film during fs-laser irradiation is not well understood. We study the thin film femtosecond-laser doping process through optical and structural characterization of silicon fs-laser doped using a selenium thin film, and compare the resulting microstructure and dopant distribution to fs-laser doping with sulfur from a gaseous precursor. We show that a thin film dopant precursor significantly changes the laser-material interactions, modifying both the surface structuring and dopant incorporation processes and in turn affecting p–n diode behavior.