Abstract
Abstract High-efficiency and high-speed photodetectors with broadband responses are playing pivotal roles for wavelength-division multiplexing optical communications. Germanium photodetectors on silicon platforms exhibit potential cost advantage due to the compatibility for monolithic integration with silicon-based electronic circuits for signal amplification and processing. In this article, we report a normal incidence, germanium photodetector enabled by guided-mode resonances in photonic crystal, which successfully resolved the compromise between quantum efficiency, wavelength coverage and bandwidth requirement, a drawback usually faced by conventional photodetectors operating at normal incidence. The resonant photonic crystal structure is designed to support multiple resonances in the target wavelength range. With an intrinsic absorption layer thickness of 350 nm, the device achieved a high external quantum efficiency of 50% at 1550 nm, along with an enhancement around 300% for the entire C-band. Using a mesa diameter of 14 μm, the fabricated device exhibited a 3-dB bandwidth of 33 GHz and obtained clear eye diagrams at bit rate up to 56 Gbps. This work provides a promising method to design high-efficiency, high-speed, normal incidence germanium photodetectors for optical interconnect systems.
Highlights
Silicon photonics is a very promising platform which can produce compact, low power, multifunctional photonic circuits and allow such photonic circuits to be built on the same chip as the microelectronics [1,2,3]
We report a normal incidence, germanium photodetector enabled by guided-mode resonances in photonic crystal, which successfully resolved the compromise between quantum efficiency, wavelength coverage and bandwidth requirement, a drawback usually faced by conventional photodetectors operating at normal incidence
Another important characteristic of guidedmode resonance (GMR) is that strong optical resonances can be achieved in photonic crystal (PhC) with only a few periods [37], which enables the use of GMRs in small-size photodetectors for high-speed applications
Summary
Silicon photonics is a very promising platform which can produce compact, low power, multifunctional photonic circuits and allow such photonic circuits to be built on the same chip as the microelectronics [1,2,3]. To overcome the trade-off between quantum efficiency and bandwidth in normal incidence Ge photodetectors, different methods have been adopted to enhance the photon responsivity. Two previous works have simulated enhanced light absorption enabled by guidedmode resonance (GMR) in Ge photodetectors [16, 17]. In these works, photonic crystal (PhC) is introduced to bring with single GMR at the target wavelength range, leading to a narrow-band light absorption enhancement. We present a normal incidence Ge-on-Si PIN photodetector with a 350 nm intrinsic layer, which employs GMRs to enhance the light absorption. These characteristics compare favorably with previous reports, as shown in Supplementary Section V
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