Optical picosecond studies of hot carriers in amorphous semiconductors

Thermalization of photogenerated carriers in a-Si, a-Si:H, a-As2Se3 and a-Se was studied by measuring the photoinduced absorption with subpicosecond resolution. The thermalization process can be described by Frohlich interaction with polar phonons in a-Si:H and a-As2Se3 but not in a-Si. Using photon energy of 2eV, the excess energy dissipation rates were determined to be 0.5 eV/ps in a-Si, 0.1 eV/ps in a-Si:H, 0.2 eV/ps in a-As2Se3 and less than 0.05 eV/ps in a-Se.