We propose an InP-based nanoscale metal-semiconductor-metal photodiode with a surface plasmon antenna composed of gold slit arrays for optical communication systems. Resonant modes of the surface plasmon antenna are numerically simulated by the finite-difference time-domain method. The calculation results suggest the advantage of the hybrid mode, which is produced by a Wood-Rayleigh anomaly mode and a vertical cavity mode. The hybrid mode enables a quantum efficiency of more than 50% when using a 250-nm-thick InGaAs absorption layer. A higher efficiency of about 95% can be achieved by combining a surface plasmon antenna with a distributed Bragg reflector consisting of 20 periods of quarter-wave InP/InGaAsP layers.
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