Efficient optical coupling in AlGaN/GaN quantum well infrared photodetector via quasi-one-dimensional gold grating.

Abstract

In this letter, a new kind of grating, quasi-one-dimensional gold grating, has been proposed to enhance the optical coupling in AlGaN/GaN quantum well infrared photodetector (QWIP). The electric field distribution, current density and energy flow are analyzed by an algorithm of finite element method (FEM). Significantly enhanced electric field component E(z) perpendicular to multiple quantum wells (MQWs) is explained by introducing the resonant coupling of surface plasmon polariton (SPP) and localized surface plasmon (LSP). The |E(z)|(2) in MQWs reaches 0.85 (V/m(2) when the electric field intensity (|E(0)|(2)) of normal incidence is 1 (V/m(2) at 4.65 μm, showing 2 times and 1.3 times increase compared with that obtained via a one-dimensional gold grating and a two-dimensional gold grating, respectively. The results confirm that the quasi-one-dimensional gold grating provides more plasma excitation source and higher charge density with structure optimization, resulting in a high optical coupling efficiency of 85% in quantum well region.