Hot-carrier thermalization in amorphous silicon

Thermalization of photoinduced carriers in a-Si and α-Si:H was studied with use of sub-picosecond-pump and probe techniques with parallel and perpendicular polarizations. The underlying process was identified as hot-carrier absorption whose cross section increases with the carrier excess energy. The energy dissipation rate in α-Si is ≈ 0.5 eV/ps (≈hv 2 phonon) and is less than 0.1 eV / ps in a-Si:H; Frohlich interaction with polar phonons can explain this smaller rate. A photoinduced dichroism associated with polarization memory was observed.