| Nanowire devices are potential building blocks for complex electronic circuitry, however, challenges such as in-place alignment, precise positioning and nanowire device integration need to be addressed. In this work selective area grown (SAG), micron sized gallium nitride (GaN) mesas were used as growth substrates for lateral epitaxial GaN nanowire arrays. The thermodynamically stable mesa facets provide a crystallographic match for directed nanowire synthesis by minimizing the surface energy at the interface between the nanowire and substrate.;Nanowires grow from the sidewalls of GaN mesas forming parallel and hexagonal networks. Alignment occurs in the nonpolar m-axis <101¯0> and semipolar <101¯1> directions respectively. Gallium nitride nanowires are interconnected between thermodynamically stable and smooth pyramidal (101¯1), and (112¯2) surfaces of adjacent GaN mesas, and they also grow from a single mesa to form free-standing nanowire cantilevers.;The synthesis of lateral free-standing nanowires has led to exciting studies of their structural, electrical, and optical properties. Characterization of the electrical properties is carried out by in situ probing of single nanowires on the growth substrate inside a scanning electron microscope (SEM). The current transport is found to be largely dominated by thermionic field emission and Fowler-Nordheim tunneling, and is significantly limited by a large contact resistance at the probe-nanowire interface. The carrier concentration and mobilities of the probed nanowires are extracted and are in agreement with standard field effects transistors (FETs) fabricated from nanowires grown using similar growth conditions. These results reveal that electrical probing of lateral GaN nanowires is a reliable means of characterizing their electrical properties once the interface resistance between the probe and nanowire is considered.;The optical properties of the nanowires were investigated. Photon emission at 3.26 eV dominated the cathodoluminescence (CL) spectra across the entire sample for both spot and wide area excitation. A weak band edge luminescence (BEL) band at 3.42 eV, and a broad weak yellow luminescence (YL) band at 2.24 eV is observed for the nanowires and is indicative of the impurities incorporated during the nanowire growth. Lastly, a proof of concept method which integrates this novel in situ aligned nanowire-mesa template for nanoelectronic device application is demonstrated. |
