Metasurfaces constructed from metallic nanostructures can be designed to operate efficiently as coupling structures for
incident optical beams to surface plasmon polaritons (SPPs) propagating thereon. On a semiconductor, metallic
metasurfaces can act simultaneously as a device electrode while ensuring strong optical field overlap with the active
region. Additionally, SPP fields thereon can be confined to sub-wavelength dimensions and significantly enhanced
relative to the exciting field. These features are very attractive for nanoscale optoelectronic device applications, such as
photodetectors and modulators. We discuss recent progress on optoelectronic metasurfaces, particularly recent device
demonstrations for high-speed reflection modulators based on a metal-oxide-semiconductor capacitor structure
exploiting the carrier refraction effect in Si, and for Schottky contact photodetectors on III-Vs and Si.