Photovoltaic Cells with CVD Diamond Films: Correlation between DLTS Spectra and Photoresponse Kinetics

Photovoltaic cells with polycrystalline and nanocrystalline CVD diamond films have been fabricated and investigated. The undoped and B-doped polycrystalline diamond films were grown on Si and W substrates by Hot Filament CVD technique, and nanocrystalline diamond films were grown on Si substrate by DC plasma CVD technique. Different after-growth treatments were applied to the films including annealing in air and etching in hydrogen or argon microwave plasma. Semitransparent Ti electrodes were deposited on top of the films, and the substrate was used as the second electrode. Interface band bending and recharging trapping center amount were shown to be strongly dependent on the specific treatment. Kinetics of the open circuit photovoltage and short circuit photoresponse at pulse illumination was measured and analyzed in comparison with DLTS spectra. The correlation between photoelectric signal decays and the DLTS spectra has 58 been found. That lets one to ascribe some of the time constants of the photoelectric signal decays to the certain trap levels in the structures, and also to make some conclusions on localization of these traps.