Enhanced absorptive characteristics of GaN nanowires for ultraviolet (UV) photocathode

Abstract

This paper focuses on the geometry of GaN nanomaterials and subsequent absorption rate analysis performed to optimize ultraviolet photocathode for operation in the wavelength range of 200–400 nm. COMSOL Multiphysics commercial software were used to numerically simulate the optical properties of GaN (gallium nitride) nanomaterials. Based on the concept of light trapping mechanism and radial mode resonance absorption, we study GaN nanomaterials with various arrangements and geometric features to obtain unified broadband light absorption in the ultraviolet region. In radial mode, we investigated the light-trapping efficiency of symmetrical and asymmetrical six-side pyramid structure nanoarrays, demonstrating broadband light absorption in two nanostructure periodic arrays (square periods and hexagonal periods) of absorbing efficiency. In the axial mode, the light absorption efficiencies of the hierarchical structures of different geometric parameters and characteristic structures are calculated and analyzed. It is interesting that GaN cylindrical–hemispherical layered nanostructure (R = 140 nm, H = 640 nm) exhibits size-dependent absorption bands and high absorption efficiency in the ultraviolet region. All the results provide an effective solution for designing GaN cathode materials in the ultraviolet omnidirectional absorption.