Resonant-cavity-enhanced subwavelength metal–semiconductor–metal photodetector

We propose a resonant-cavity-enhanced subwavelength metal–semiconductor–metal structure for efficient and ultrafast photodetection. A Fabry–Pérot cavity is composed by a bottom multilayer Bragg reflector and a top subwavelength metallic grating. The structure was fabricated on a GaAs substrate with 75 nm finger width and finger spacing, and theoretical results were validated experimentally by reflection spectra and photocurrent measurements. 75% efficiency is predicted theoretically in a 40-nm-thick GaAs layer, leading to potential cutoff frequencies between 300 and 500 GHz in TE polarization.