Robust Si/Ge heterostructure metasurfaces as building blocks for wavelength-selective photodetectors

We present a design for silicon-compatible vertical Germanium pin photodiodes structured into all-dielectric metasurfaces. Proof-of-principle metasurfaces are fabricated on silicon-on-insulator wafers in a top-down process. Simulations and measurements of the spectroscopic properties, specifically the absorption, show high spectral selectivity, and absorption efficiencies as large as those in bulk Germanium layers with about four times the Ge layer thicknesses. Our metasurface structures can be tuned to the target wavelength through tailoring of the lateral geometry. Possible applications include spectroscopy and hyperspectral imaging, with several metasurfaces for different wavelength ranges integrated with readout circuitry into a low-cost electronic-photonic integrated circuit.