Reflection from bare and gold coated InP nanowire arrays*

We investigated the spectral and angle resolved reflectance from bare and gold coated (plasmonic) InP nanowire (NW) arrays which were grown by selective area epitaxy. The NWs in the arrays have diameters of 180 nm, heights of ~2 and ~1 micrometers and a pitch of 666 and 500 nm (named areas NWA-1 and NWA-2), respectively. In NWA-2 the NWs additionally possess a 10 nm thick surrounding Al₂O₃ layer to reduce surface state and metal induced band-bending. A nominally 10 nm thick gold layer was deposited around the NWs in both arrays to study the influence of plasmonic effects. The NW arrays were illuminated with a cw laser at 880 nm for the angle resolved reflectance measurements and with an incandescent light sourced ranged from 500 nm to 1000 nm spectrally resolved experiments. The incident light beams were polarized in p- and s-orientation. The measured spectral and angle resolved reflectance of both uncoated arrays is in very good agreement with finite-difference-time-domain (FDTD) simulations. The experimental results of the gold coated nanowire arrays reveal deviations compared with the FDTD calculations which is tentatively attributed to the granularity of the deposited gold films.