A Comprehensive Study on the Impact of Various Nano-gratings on MSM-PDs for Enhancement in the Light Absorption

Abstract

In this paper, we have analyzed metal-semiconductor-metal photodetectors (MSM-PDs) with different nano-grating structures or shapes to improve the light absorption capacity into the device in details for high-speed communication systems and networks. The plasmonic-based MSM-PD structure demonstrates a significant improvement in light absorption capacity for the developed device compared to conventional MSM-PDs i.e., devices that have not employed the nano-gratings. The light absorption capacity of the device is varied with the variation of geometrical shapes and parameters of the nano-gratings, such as the nano-grating height, slit width and so on. These nano-grating structures are assisting in light transmission through the central slit (i.e., subwavelength apertures) efficiently, resulting in the excitation of surface plasmon polaritons (SPPs) as the incident photons interact with the nano-gratings/ nano-corrugations. This improved light transmission in the central slit along with excited SPPs results in resonant light absorption in the device. This means the light trapped inside the central slit is triggered by the SPPs to a higher order magnitude. This causes the light absorption enhancement for the device, i.e., more light is transmitted through the device instead of reflecting back to the surface. The simulation results demonstrated that the light absorption enhancement factor (LAEF) for these devices have improved dramatically due to the nano-gratings. For modeling and simulation of these devices, Opti-FDTD tool is used which is based on finite difference time domain (FDTD) method. The application of these simulated devices is in the range of 800-850-nm. The simulation results are suitable for the design of nano-structured MSM-PDs that can be used in high-speed communication systems and sensor network systems.