Analytic formulas and numerical simulations for non-uniform AlxGa1-xN nanostructure on electro-optical properties for UV Photodetectors

• Published in: Optics communications Vol. 486; p. 126799
• Main Authors: Lv, Zhisheng, Liu, Lei, Zhangyang, Xingyue, Sun, Yan, Lu, Feifei, Tian, Jian
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.05.2021
• Subjects: COMSOL multiphysics; Gradient Al component AlxGa1-xN; Nanostructure; Optical absorption; Quantum efficiency; UV photocathode; Nanostructure; Quantum efficiency; Gradient Al component AlxGa1-xN; UV photocathode; Optical absorption; COMSOL multiphysics
• ISSN: 0030-4018; 1873-0310
• DOI: 10.1016/j.optcom.2021.126799

In this paper, we numerically studied the influence of the geometry of gradient Al component AlxGa1-xN nanowires on their optical response. Based on the finite element simulation software COMSOL Multiphysics, we systematically studied the influence of geometric parameters of base radius (R), nanowires spacing and angle of incident light (AOI) on the optical response. To this end, we designed various gradient Al component AlxGa1-xN nano-trapped structure in the wavelength range of lambda (300–400 nm). The simulation results show that the optimal optical absorption spectra of hexagonal pyramid nanostructure arrays range from 300 to 400 nm and the average optical absorption efficiency is 97.87%, achieving omnidirectionality and unified broadband light absorption for AlxGa1-xN ultraviolet photocathode. In addition, we adjust the distribution and thickness of the Al component in the nanowires to achieve the optimization of the quantum efficiency and collection efficiency of the gradient Al component AlxGa1-xN. Using Spicer’s three-step emission theoretical model, the photoemission efficiency of variable Al component AlxGa1-xN nanowires array was calculated. As a result, when the Al component range is 0–0.19, the external electric field is 2.5 (V/μm) and the sublayer thickness is 60 nm, 120 nm, 180 nm, 240 nm, respectively, the optimal quantum efficiency of the AlGaN photocathode is 38.16% and the optimal collection efficiency is 31.12%. All these findings not only indicate that the gradient Al component AlxGa1-xN material has great potential advantages for UV band detection, but also provide theoretical support for the experiment and preparation of AlGaN photocathodes. •In this paper, a non-uniform AlxGa1-xN nanostructure with graded Al component arrangement is proposed as light-trappers for the UV photocathode.•For gradient Al component AlxGa1-xN material data, we divide different Al component into 8 components in a top-down order to the nanowire cells.•Optical absorption, external electric field, quantum efficiency and collection efficiency of various AlxGa1-xN nanostructures are discussed.•When the Al composition range is 0-0.19, the external electric field is 2.5 (V/μm) and the thickness of the sublayer (60 nm, 120 nm, 180 nm, 240 nm), the optimal quantum efficiency of the AlxGa1-xN nanowire can be obtained.•For non-uniform nanoarrays, the optimal light absorption of the non-uniform hexagonal pyramid AlxGa1-xN nanoarray can reach 97.87%.