Optical dispersion relations in two types of amorphous silicon using Adachi's expression

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 (Eg) and damping (or broadening, Γ) energies. Eg 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.