Effect of plasma dynamics on gallium nitride nanorod and growth by molecular beam epitaxy

GaN is a wide bandgap semiconductor known for its use in high-frequency switching electronics and laser diodes, its stability as a high-temperature transistor material, and a radiation resistance which makes it an ideal material for space applications. Additionally, the discovery of the bandgap tunability of nitride materials using GaN has led to successful development of adjustable wavelength LED devices. However, the success of devices far outpaces the understanding of their material growth, making advances difficult to build upon. Plasma- Assisted Molecular Beam Epitaxy (PA-MBE) is an ideal growth method for achieving very precise structures for detailed study. Although plasma itself is a well-studied field, comprehensive understanding of its relation to these growth processes is crucial to connect the fields of plasma physics and material deposition. In this study, we examined GaN nanorods grown by PA-MBE under varying plasma power, and measured the visible emission spectra from the plasma. We parametrized the ground and excited states of the plasma by fitting the spectra using the Specair software, which enabled an analysis based on all emissions within the visible spectrum. Using the sensitivity of GaN nanorod morphology to the mechanisms by which they grow, we compared the plasma parameters to the resultant material's epitaxial qualities. Nucleation, growth and evolution of GaN which is made defective by excess with various nitrogen plasma generation conditions was studied. The most probable nitrogen species carrying energy to the growth surface are identified and compared to corresponding material characteristics.