Excellent Light Confinement of Hemiellipsoid- and Inverted Hemiellipsoid-Modified Semiconductor Nanowire Arrays

In this paper, we introduce hemiellipsoid- and inverted hemiellipsoid-modified semiconductor nanowire (NW) optical structures, and present a systematic investigation on light management of the corresponding arrays based on GaAs. It is found that the modification makes well utilization of light scattering and antireflection, thus leading to excellent light confinement with limited effective thickness. For example, 90% and 95% of the incident photons with the energy larger than the bandgap energy can be trapped by the inverted hemiellipsoid-modified NW arrays with the effective thicknesses of only ~ 180 and 270 nm, respectively. Moreover, excellent light confinement can be achieved in a broad range of the modification height. Compared to the corresponding array without top modification, spatial distribution of the photo-generated carriers is expanded, facilitating carrier collection especially for the planar pn junction configuration. Further investigation indicates that these composite nanostructures possess excellent omnidirectional light confinement, which is expected for advanced solar absorbers.