Reactive Magnetron Sputtering as a Growth Alternative for Gallium Nitride Nanowires

Abstract

<p>Gallium nitride (GaN) nanowires are high-performance materials with wide, direct bandgaps and superior electronic properties. Although their properties make them of great interest for next-generation technologies, widespread adoption has been limited by expensive production processes. Here, the results of growing GaN nanowires via DC magnetron sputtering at different temperatures and using different metal catalysts are reported.</p> <p>A new substrate heater was designed to minimize contamination from the heater filament and increase the substrate temperature window to in excess of 800°C. Sixteen-mm² (111) silicon samples had one-to-four nm of a metal catalyst deposited on them using evaporation. This metal catalyst layer (gold, platinum, or nickel) was employed to induce catalyst-assisted vapor-liquid-solid nanowire growth. GaN was deposited via a reactive nitrogen DC magnetron sputtering system. Surface morphology and composition were analyzed using both scanning and transmission electron microscopy. Energy-dispersive x-ray spectroscopy (EDS) and electron energy loss spectroscopy were used to measure the presence of gallium and nitrogen in the resulting nanowires, respectively.</p> <p>This furnace significantly reduced tungsten contamination to below the detectable levels of EDS. GaN nanowires were present on gold-catalyzed samples only in the gold-covered region of the silicon substrate exposed to a gallium flux. Nanowire morphology improved as temperature was elevated, but it did so at the cost of lower areal density. Conversely, platinum-coated samples yielded fewer nanowires than their gold-coated counterparts. Samples that had nickel deposited on them displayed the best GaN nanowire growths. They had the best surface morphologies, had negligible oxygen concentrations, and were single crystalline.</p>