Germanium-on-silicon nitride waveguides for mid-infrared integrated photonics

TLDR

The study simulates a germanium‑on‑silicon nitride waveguide to verify its feasibility for mid‑infrared photonics. The waveguide is fabricated by bonding a silicon‑nitride‑deposited germanium‑on‑silicon donor wafer onto a silicon substrate, then performing a layer‑transfer process and chemical‑mechanical polishing to remove misfit dislocations, yielding a scalable, high‑quality germanium‑on‑silicon nitride structure. The germanium‑on‑silicon nitride waveguide exhibits a propagation loss of 3.35 ± 0.5 dB/cm and a bend loss of 0.14 ± 0.01 dB per 5 µm radius bend at 3.8 µm, demonstrating a low‑loss, high‑contrast platform for mid‑infrared integrated photonics.

Abstract

A germanium-based platform with a large core-clad index contrast, germanium-on-silicon nitride waveguide, is demonstrated at mid-infrared wavelength. Simulations are performed to verify the feasibility of this structure. This structure is realized by first bonding a silicon-nitride-deposited germanium-on-silicon donor wafer onto a silicon substrate wafer, followed by the layer transfer approach to obtain germanium-on-silicon nitride structure, which is scalable to all wafer sizes. The misfit dislocations which initially form along the interface between germanium/silicon can be removed by chemical mechanical polishing after layer transfer process resulting in a high-quality germanium layer. At the mid-infrared wavelength of 3.8 μm, the germanium-on-silicon nitride waveguide has a propagation loss of 3.35 ± 0.5 dB/cm and a bend loss of 0.14 ± 0.01 dB/bend for a radius of 5 μm for the transverse-electric mode.