Light Absorption and Reflection in Nanostructured GaAs Metal-Semiconductor-Metal Photodetectors

Nanostructured metal-semiconductor-metal photodetectors (MSM-PDs) can assist in future high-speed communication devices for achieving high responsivity-bandwidth characteristics. We numerically evaluate the periodic nanotextured structures that provide for the confinement of light and concentration of energy near the designed wavelength, a feature attributed to surface plasmon polaritons. This plasmonic-based miniaturization provides a new approach to investigate remarkable optical properties of nanoscale device structuring. A finite-difference time-domain method is used to calculate the maximum light absorption and reflection of nanograting-assisted MSM-PDs by varying detector's physical parameters in comparison with a conventional device. The horizontal and vertical surface resonances are identified as the key mechanisms to excite the surface waves with the aid of normally incident TM-polarized light. The extraordinary optical transmission is notably enhanced by optimizing the grating parameters and light incident angles. The simulation results are presented for light absorption and reflection in the subwavelength region of nanograting-assisted MSM-PDs compared with the conventional MSM-PDs.