Analysis of a-Si:H subgap absorption spectra obtained from absolute cavity ringdown absorption spectroscopy using an empirical DOS model

The novel thin film cavity ringdown absorption technique in combination with transmission reflection spectroscopy has been employed to obtain absolute absorption spectra of a-Si:H films of 4 nm and 1031 nm thickness between photon energies of 0.7 and 4 eV. Using an empirical density-of-states (DOS) model the absorption spectra have been deconvoluted and the DOS for both films could be determined within conceivable limits. The DOS for the bulk and surface dominated films are clearly different and the dipole matrix elements for the different transitions as well as the resulting dipole matrix function is discussed.