UV photosensing characteristics of nanowire-based GaN/AlN superlattices

arXiv:1604.07978v2We have characterized the photodetection capabilities of single GaN nanowires incorporating 20 periods of AlN/GaN:Ge axial heterostructures enveloped in an AlN shell. Transmission electron microscopy confirms the absence of an additional GaN shell around the heterostructures. In the absence of a surface conduction channel, the incorporation of the heterostructure leads to a decrease of the dark current and an increase of the photosensitivity. A significant dispersion in the magnitude of dark currents for different single nanowires is attributed to the coalescence of nanowires with displaced nanodisks, reducing the effective length of the heterostructure. A larger number of active nanodisks and AlN barriers in the current path results in lower dark current and higher photosensitivity and improves the sensitivity of the nanowire to variations in the illumination intensity (improved linearity). Additionally, we observe a persistence of the photocurrent, which is attributed to a change of the resistance of the overall structure, particularly the GaN stem and cap sections. As a consequence, the time response is rather independent of the dark current.Financial support from the EU ERC-SG “TeraGaN” (#278428) and ANR JCJC COSMOS (ANR-12-JS10-0002) is acknowledged. Furthermore, the groups in Grenoble and Giessen received traveling support from the DAAD/Campus France program Procope. P.H., J.S., and M.E. acknowledge financial support within the LOEWE program of excellence of the Federal State of Hessen (project initiative STORE-E). M.d.l.M. and J.A. acknowledge funding from Generalitat de Catalunya 2014 SGR 1638 and the Spanish MINECO MAT2014-51480-ERC (e-ATOM) and Severo Ochoa Excellence Program.Peer Reviewe