The femtosecond pump and probe technique with 2eV and 4eV photons was applied to the study of hot photocarriers with considerable excess energy in extended states of a-Si:H and a-Ge:H. Photoinduced changes in the complex dielectric constant ε1 + iε2 were calculated from the measured changes in reflectivity ΔR and transmission ΔT. This technique enables us to estimate that the average carrier cooling rates in our a-Si:H and a-Ge:H samples are about 2eV/psec and 1eV/psec, respectively. Photoinduced bleaching associated with the filling of band states dominates over intraband contributions to Δε1 and Δε2 for photon energies significantly exceeding the bandgap.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Materials Chemistry