Molecular Beam Epitaxial Growth & Characterization of Nitride Nanowires

Currently, 21% of the world's electrical energy is used in artificial lighting. White light LEDs, the holy grail of lighting, are currently the subject of research toward efforts to reduce this alarming percentage. One method of realizing a white light emitter is to combine red, green, and blue LEDs. The Achilles' heel of this method is the 'green gap' in current LED technologies. Due to large lattice mismatch between materials with bandgaps near those needed for green emission and popular epitaxial substrates, dislocations prevent fabricating materials with high optical efficiencies. This research focuses on growing Nitride nanowires as a potential material solution to this challenge. The nanowires grow as three dimensional pillars and therefore their lattice constants can relax more closely to their inherent values. This will allow for the growth of material free from dislocations. Specifically in this work, GaN and InGaN nanowires were successfully grown on Silicon substrates. Data on the characterization of the Molecular Beam Epitaxy grown InGaN wires, which are the first ever reported, reveal they are of high structural quality. The InGaN nanowires show Indium concentration gradients which result in a broad optical spectrum. The internal quantum efficiency of the InGaN material was found to be 8%. Siliconitride nanowire p-n junctions were grown and fabricated for the first time in Nitride MBE nanowire technology using p-type Silicon. Further, Nitride nanowire growth by MBE on ALD oxides of precisely controlled thickness has been reported here for the first time. Success in the growth of Nitride nanowires on controlled oxides has led to the first ever reported Silicon/oxideitride nanowire heterostructures. Also reported for the first time is the observation of the quantum confined Stark effect in nanowire multi quantum well structures.