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

Abstract

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.

Waveguide-Integrated Ge/Si Avalanche Photodiode with Vertical Multiplication Region for 1310 nm Detection

“…This method can directly achieve ultra-high-quality, single-crystalline optical layers on diverse arbitrary optical templates for photodetection and beyond. The other is subwavelength photonic structure-enhanced photodetectors [38,39]. Table 1 provides a summary of the reported Ge/Si APDs, including the structure and process complexity and the overall performance of the APD proposed in this work by comparing the key parameters with the other reported waveguide-integrated Ge/Si APDs.…”

Strong Optical Coupling of Lattice Resonances in a Top-down Fabricated Hybrid Metal–Dielectric Al/Si/Ge Metasurface

“…We note that the presence of a microscope objective in the FT-IR setup leads to a distribution of incidence angles for the incident light. The absorptance was obtained using a deembedding approach that takes into account multiple reflections in the underlying substrate layers …”

“…Field confinement in Ge is affected not only by the presence of the Si spacer layer between the Al disk and the Ge nanocylinder, but also by the continuous Si layer below the Ge nanocylinders. This can lead to an impact of the etching depth on optical properties of the metasurface . Indeed, the spectral position of the MQ-CLR is strongly influenced by the etching depth: The presence of a continuous Si layer underneath the Ge disks mediates coupling between the disks as indicated by the presence of a nonvanishing electric field amplitude within the bottom Si layer at resonance (Figure ).…”

“…Device integration typically requires the use of continuous contacting layers that connect all individual elements of the metasurface, however, the presence of these continuous layers can be detrimental to the optical properties of metasurfaces by making those highly susceptible to variations in the fabrication process . In our structures, the dependence of the optical properties of the metasurface on the structure of a continuous connecting layer can be exploited for tunable metasurfaces.…”