| Alloys of Group IV elements have been routinely studied because new materials can be developed for microelectronic applications in extreme environments, high frequency applications, high efficiency optoelectronic devices or high power density circuits. One of the greatest practical benefits of these materials is that they can be made to work with established Si fabrication technologies, thus greatly reducing the difficulty in manufacturing devices made from these materials. However, there is a Group IV alloy that has remained virtually unexplored, the crystalline Ge:C system, as Ge and C are insoluble in one another at all temperatures and pressures. However, it has been demonstrated that metastable crystalline Ge1−xCx thin films can be produced with limited success. These materials are of great interest because they can potentially offer the superior mobility and optical characteristics of Ge as compared to those of Si, while the addition of C can raise the bandgap and reduce the lattice constant of the material to be comparable to those of Si. The work presented here uses ECRPECVD processing to grow crystalline Ge1−xCx films on Si wafers. The first stage of the work is designed to study the characteristics of the plasma source and how the plasma processing parameters affect the material properties of the resulting films. The basic material, optical and electrical properties of the films were studied to build a knowledge resource on this new material. For comparison and to deepen the understanding of the nature of the alloy, pure Ge films were grown with similar parameters to the Ge1−xC x alloy films. The films are characterized by UV/VIS/NIR Spectroscopy, Raman spectroscopy, x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy, four point probe conductivity and Hall mobility measurements. The second stage of the research was to dope the material n and p type and to determine the affect on the electrical properties. The final stage was to use the knowledge obtained from the above work to develop novel multi-layer structures that optimize the desirable material properties and to develop a ‘proof of concept’ diode in the crystalline Ge1−x Cx material, which was the first microelectronic device fabricated in this material. |
