Ultrafast carrier dynamics of aluminum-doped silicon film irradiated by femtosecond laser pulse

An aluminum-doped p-type polycrystalline silicon film was fabricated on a glass substrate using magnetron sputtering. The ultrafast carrier dynamics of the silicon film were studied via its femtosecond transient reflectivity characteristics. The analysis of the transient reflectivity signal shows that the fast component of the relaxation time tau(f) is shorter than that found in previous studies with undoped silicon. The dynamics of the free carrier response and state filling dominate tau(f) in this sample, and owing to the existence of defects and boundaries, the state filling effect significantly increases tau(f). On a longer time scale, the Auger recombination and carrier diffusion dominate the relaxation process. The slow component of the relaxation time tau(s) is also shorter than any previously reported values for undoped silicon films.