Center for Functional Nanomaterials Seminar

Gallium nitride (GaN) is an important direct wide-bandgap (3.4 eV) semiconductor for short wavelength optoelec-tronics and high power device applications. While its cost-effective bulk crystal growth is not quite available under the present technology, heteroeptiaxial GaN film growth using foreign growth substrates, such as sapphire and silicon carbide (SiC), dominates industries. However, these foreign substrates induce large concentration of dislocations (as high as 1010 cm-2 level) in the grown GaN, decreasing device performance and lifetime. The large mismatch in lattice constant and thermal expansion coefficient is the usual suspect. GaN nanowires (NW) in this sense provide superior structural integrity and potentially more efficient optoelectronic characteristics compared with their “epi-grown” counterparts since they contain virtually no dislocations. Their naturally small size renders GaN NWs promising candidates as nanoscale building blocks in optoelectronic devices patternable on various substrates, if the NWs can be combined with practical large-scale patterning techniques.
Under these basic motivations, my Ph.D research project covered GaN NW growth, demonstrative unit-device fabrica-tion and material/device parameter characterization [1-7]. This presentation will focus on the topics of growth and morphology control of GaN NWs, device fabrication using focused ion beam (FIB) metal deposition technique and contact conduction mechanism analysis, and NW resonant electromechanical properties. I will also briefly describe work-in-progress on fabricating GaN nanowire light-emitting-devices.