High-Aspect-Ratio GaN p–i–n Nanowires for Linear UV Photodetectors

Ultraviolet GaN photodetectors based on nanowires (NWs) fabricated by top-down strategies promise improved uniformity, morphology, and doping control with respect to bottom-up ones. However, exploiting the advantages of the NW geometry requires sub-wavelength NW diameters. We present fabrication of large-area sub-200 nm diameter top-down GaN p–i–n NW ultraviolet photodetectors with lengths over 2 μm produced from a planar specimen using nanosphere lithography, followed by a combination of dry and crystallographic-selective wet etching. Photocurrent measurements in single-NW devices under bias show a linear response as a function of the optical power, with increased current levels under reverse bias. The linearity proves that the drift of photogenerated carriers at the junction is the dominating photodetection mechanism, with negligible contributions from surface effects. These results demonstrate that the unique properties of NW-based photodetectors can be assessed through a scalable and low-cost fabrication process.