Se doping of silicon with Si/Se bilayer films prepared by femtosecond-laser irradiation

Se doped silicon is fabricated by femtosecond-laser irradiation in the presence of Si/Se bilayer films. The enhancement in infrared absorption and carrier density is achieved by sputtering a Si thin film onto the Se film before femtosecond-laser irradiation. The effects of laser micro-structuring conditions (scanning speed and laser fluence) on surface morphology, optical and electronic properties of Se doped silicon are also studied. With the decrease of scanning speed, the absorptance increases at wavelengths from 0.4 to 2.2 µm, while the carrier density and mobility follow an opposite tendency. The optical absorption and sheet carrier density for sample fabricated at the fluence of 4.5 kJ/m2 are greater than that of samples prepared at other fluence. This experimental method facilitates the application of hyperdoping of silicon with Se in optoelectronic devices.