| This dissertation presents a study on the fabrication of zinc nitride and zinc oxy-nitride films, and related hetero-structures on glass, silicon and other substrates. The goals of this study include gaining fundamental understanding on the electrical and optical properties, the chemical-bonding states and the micro-structure of these materials and examining their potential for photovoltaic and other electronic and optoelectronic applications.;Reactive radio-frequency (RF) magnetron sputtering was used as the deposition method, which potentially enables control of composition of the thin films, as well as fabrication of multilayer structures for the study of possible hetero-junctions between zinc nitride and zinc oxy-nitrides. Along with reactive sputtering, several other fabrication methods, such as thermal evaporation and solution (e.g. silver or carbon paste) painting, were used as auxiliaries where necessary. The characterization techniques employed include (i) x-ray based techniques (x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), energy dispersive x-ray spectroscopy (EDXS)), (ii) optical based methods (spectroscopic ellipsometry (SE), optical spectrophotometry, Raman spectroscopy), (iii) scanning electron microscopy (SEM), and (iv) electrical measurements (resistivity, Hall effect measurements, current-voltage and photovoltaic measurements).;The cross-correlation between the deposition/post-deposition conditions and the physical properties of the films was investigated. The deposition conditions, such as the nitrogen (or oxygen) partial concentration in the sputtering gas mixture, substrate temperatures, total deposition pressure, as well as the post-deposition treatments such as thermal treatment and/or oxidation in ambient, were studied in detail. Zinc nitride, with a small fraction of "naturally" incorporated oxygen, is found to be a promising candidate for photovoltaic applications because of its optical and electrical properties. Also, the capability of property tuning for the zinc oxy-nitride material system was demonstrated by intentionally introducing varied amount oxygen into zinc nitride.;In order to better understand the crystalline structure and the electronic band structure of these materials, first principle density functional theory (DFT) was used for computations of pure zinc nitride and the doping effects in it with both native elements (Zn, N) and copper family elements (Cu, Ag, Au) as possible p-type dopants. Atomic geometry, formation energy, as well as electronic structure of defects in zinc nitride were studied and a general consistency was observed between theoretically calculated and experimentally determined results. Defect density of states (DOS) suggest that among all three studied copper-family elements, copper is a good candidate for a p-type dopant.;Technological insight and approaches to the fabrication of device-relevant structures were the other important outcomes of this work. Our studies showed that the fabrication of device-relevant ohmic contacts, rectifying metal-nitride junctions and p-n junctions was possible. Substantial photovoltaic action was observed in a single junction solar cell configuration that uses p-type zinc oxy-nitride as an absorber layer. |
