Combining Metal Dewetting and Lateral Etching for the Scalable Top-Down Fabrication of GaN Nanowire Arrays with Independently Tunable Diameter and Spacing

The top-down fabrication of nanowires based on patterning via metal dewetting is a cost-effective and scalable approach that is particularly suitable for applications requiring large arrays of nanowires. Advantageously, the nanowire diameter can be tailored by the initial metal film thickness. However, we show here that metal dewetting inherently leads to a coupling between the nanowire diameter and spacing, with an analogous coupling to the pitch. To overcome this limitation, we introduce two strategies that are exemplified for GaN nanowires: (i) modification of the surface and interface energies within the dewetting system and (ii) thinning of the nanowires by lateral etching. In the first strategy, GaN(0001), SiOx, and SiNx substrate surfaces are combined with Au, Pt, and Pt–Au alloy dewetting metals to tune the dewetting behavior. The differences in interface energies affect the relation between the nanowire diameter and spacing/pitch, albeit within a limited range. The second strategy adds a lateral etching step to the conventional top-down nanowire fabrication process. This step, at the same time, reduces the nanowire diameter and increases the spacing (whereas pitch is not affected), thus enabling combinations beyond the constraints of metal dewetting alone. When in addition different initial nanowire diameters are employed, it is possible to independently control the diameter and spacing over a substantially extended range. Therefore, the inherent limitation of conventional dewetting-based patterning approaches for the top-down fabrication of nanowires is overcome.