Using Adachi’s expression [S. Adachi, Phys. Rev. B 43, 12 316 (1991)] for the complex dielectric function of amorphous semiconductors, we fit out experimental results [M. Fried et al., J. Appl. Phys. 71, 5260 (1992)] for two different types (self-implanted and implanted-annealed or relaxed) of amorphous silicon. The complex dielectric functions were determined by spectroscopic ellipsometric measurements in the visible wavelength region. The fit resulted in different optical band gap (${\mathit{E}}_{\mathit{g}}$) and damping (or broadening, Γ) energies. ${\mathit{E}}_{\mathit{g}}$ is lower and Γ is higher in implanted a-Si. Both changes can be interpreted by the presence of more structural disorder point defects in implanted a-Si compared with relaxed a-Si.

• Received 26 August 1993

DOI:https://doi.org/10.1103/PhysRevB.49.5699