Optimization of Optical Absorber in Plasmonic Detector Structures Using Gratings in NIR

The improvement of light absorption is a major change for optical detectors. In this research, a metal-semiconductor-metal photodetector with a patterned metal grating was investigated and the gating was optimized for better light absorption in the near-infrared region. The designed structure consists of a gallium arsenide semiconductor as substrate, a SiO2 layer as insulator and a patterned gold (Au) as metal lattice. The main phenomena for the enhancement of light absorption in this structure are the resonance of the lattice and the propagation of plasmonic waves along the metal contacts and the insulator boundary, as well as the coupling of more light into the semiconductor, which leads to higher carrier generation. The structure with a different number of gratings with fixed grating periodicity (300 nm) was simulated using the finite-difference time-domain method in the Lumerical software. The simulation results show that the maximum absorption occurs in wavelength 840 nm with 8 gratings on each side of the surface of the device.