Optimized design of gradient Al component AlxGa1-xN nanostructure with hexagonal periodic arrangement for enhanced optical absorption of ultraviolet photodetectors

Abstract

A three-dimensional electromagnetic field model has been developed to study the photon capture properties of gradient band-gap AlxGa1-xN nanomaterials with built-in electric field using COMSOL Multiphysics commercial software based on finite element numerical simulation. Based on the phototrapping mechanism and the concept of radial mode resonance absorption, we studied AlxGa1-xN nanomaterials with different cross-section shapes and Al component distributions to obtain broad-band and omnidirectional light absorption in the ultraviolet band. In this process, based hexagonal periodic arrangement, we simulated and analyzed the optical responses of cones, hexagonal pyramids and hexagonal prisms structure, including optical absorption, quantum efficiency, electric field distribution and generation rate distribution. The results show that the non-uniform pyramid structure can effectively enhance the optical absorption efficiency at FR = 0.9. The photon generation rate of the pyramid nanostructure is mainly distributed in the cathode nanostructure part, which is significant for improving the emission efficiency of cathode electrons. In addition, we investigated the optical properties of AlxGa1-xN nanostructures by changing the distribution of Al component and the thickness of different sublayers. As a result, the prism structure achieves optimal optical absorption and quantum efficiency when the Al component ranges from 0 to 0.75. Although a strict three-dimensional AlGaN NWAs array model has been established in this work, it is still necessary to demonstrate the experimental results. In the future research, we will experimentally study the effect of different geometric shapes on UV photocathode.