Growth of undoped and doped IIInitride nanowires and their characterization

In the twenty first century, the rapid development of science, engineering and technology is blessed by the application of nanotechnology. It has become an attractive field of research among the scientists and created a lot of attention of the general public. Fabrication and characterization of various kinds of nanostructures such as carbon nanotubes, quantum wires and dots etc. have enabled to realize the possible applications as the building blocks of new structures and devices. Among those nanostructures, nanowires (NWs) are particularly attractive for future nanotechnology application due to their unique properties. For opto-electronic application, III-Nitride NWs are expected to further improve the performance and efficiency of optoelectronic device structures. III-Nitride NWs (GaN and InN) have been grown on different substrates by Plasma-assisted Molecular Beam Epitaxy (PAMBE). It has been found that the change of growth parameters (e.g. III-V ratio, growth temperature etc.) greatly influences the morphology of NWs. Nitrogen-rich condition is necessary to have columnar growth for both GaN and InN NWs as the surface diffusivity is reduced and the anisotropic growth is initiated. Various growth conditions for NW growth will be explained later on. A systematic analysis is carried out to understand the nucleation process for GaN NWs. For this purpose, a set of samples has been grown at different duration and their Scanning Electron Microscopy (SEM) images have been studied. The density of the wire increases with time until it saturates. A long incubation time indeed results as each wire has different nucleation time. A linear relationship between length and diameter has been established for well-nucleated wires in the nucleation stage. This helps to estimate the critical diameter for the nucleation cluster and it is found to be about 15 nm. Growth modeling of NWs has been performed by taking into account two different growth mechanisms: one is the direct impingement, which is independent of the diameter of ...