A NOVEL-APPROACH TO THE ANALYSIS OF SUB-BANDGAP ABSORPTION IN A-SI-H BASED MATERIALS

A novel analysis is proposed for obtaining sub-bandgap absorption spec tra in a-Si:H from the dual beam photoconductivity (DBP) technique in which the densities and distributions of gap and extended states are d erived from the analysis of the optical constants between 0.8 and 2 eV . This sub-bandgap absorption analysis overcomes the difficulties due to interference fringes by taking into account the multiple reflection s that an present in both the optical and the DBP spectra. This result s in a highly accurate methodology for normalizing the DBP spectra to those obtained with transmission and reflection measurements as well a s allowing films to be studied whose thicknesses are close to those us ed in solar cell and thin film transistor structures.