Femtosecond carrier dynamics in implanted and highly annealed polycrystalline silicon

Abstract

We have studied the ultrafast optical response of highly implanted and highly annealed polycrystalline silicon films using 400 nm ultrashort amplified pulses with fluence ranging between 8 mJ cm−2 to 56 mJ cm−2. Transient reflection measurements reveal differences both in the short and long temporal behaviour between the implanted non-annealed and annealed samples. Important contributing factors to the dynamics of the non-annealed sample are the carrier recombination centres and traps induced by ion implantation. In contrast to the non-annealed sample, the Auger recombination process is a key factor in the dynamics in the first few picoseconds for the sample annealed at 1100 °C. A model based on two coupled differential equations has been employed to investigate in detail the carrier dynamics in these systems. Parameters including carrier trapping times, diffusion coefficients and the Auger coefficient have been extracted.