Responsivity enhancement in metal-semiconductor-metal photodetector with nanometer fingers

InGaAs metal-semiconductor-metal (MSM) photodetectors are one of the promising devices for 1.55 /spl mu/m lightwave communication systems because of their high-speed performance derived from the low capacitance per unit area. Since the MSM photodetector is illuminated through the top finger electrodes, electrodes block a fraction of the incident light. Due to shadowing by electrode, the responsivity of MSM photodetector is low and the low responsivity is an obstacle for real system implementation. Since the internal efficiency is determined by material and thickness of absorption layer, the responsivity is controllable by the electrode structure. The responsivity can be increased by reducing finger width.