Metal Nano-Grating Optimization for Higher Responsivity Plasmonic-Based GaAs Metal-Semiconductor-Metal Photodetector

To improve the responsivity of the metal semiconductor metal photodetector (MSM-PD), we propose and demonstrate the use of sub-wavelength slits in conjunction with nano-structured the metal fingers that enhance the light transmission through plasmonic effects. A 4-finger plasmonics-based GaAs MSM-PD structure is optimized geometrically using a 2-D Finite Difference Domain (FDTD) method and developed, leading to more than 7-times enhancement in photocurrent in comparison with the conventional MSM-PD of similar dimensions at a bias voltage as low as 0.3 V. This enhancement is attributed to the coupling of the surface plasmon polaritons (SPPs) with the incident light through the nano-structured metal fingers. This work paves the way for the development of high-responsivity, high-sensitivity, low bias-voltage high-speed MSM-PDs and CMOS-compatible GaAs-based optoelectronic devices.