High-power Ge photodetector for silicon photonics has a 35 GHz bandwidth

July 11, 2016
A new Ge photodetector achieves a bandwidth of greater than 35 GHz and a maximum current density of 1.152 mA/μm3.

Silicon (Si) photonic circuits are now widely used for optical interconnects and are being actively developed for many communications, instrumentation, and scientific applications. Active photonic circuit components that, like Si, are made of IV semiconductors—in particular, germanium (Ge)—are easier to integrate than are other semiconductors such as III-V semiconductors (gallium arsenide and so on). As a result, Ge photodetectors, and in particular Ge waveguide coupling detectors, are the subject of much research to improve their bandwidth and saturation power. Researchers from Huazhong University of Science and Technology and Wuhan Research Institute of Posts Telecommunications (both in Wuhan, China) have now demonstrated a Ge photodetector that achieves a bandwidth of greater than 35 GHz and a maximum current density of 1.152 mA/μm3.

The polarization-insensitive device is based on a lumped structure containing two parallel and two related Ge absorption regions sharing the same signal and ground electrodes, which halves the total junction resistance, allowing the absorption region to be doubled to achieve higher power while maintaining bandwidth. A four-port 2D grating guides light into both sides of the Ge regions to use them to the fullest. The bandwidth of 35.84 GHz was measured under a 3 V bias voltage and 0.42 mA photocurrent—the responsivity of the device was 1.06 A/W under these conditions. Reference: G. Chen et al., Opt. Express (May 2, 2016); doi:10.1364/oe.24.010030.

About the Author

John Wallace | Senior Technical Editor (1998-2022)

John Wallace was with Laser Focus World for nearly 25 years, retiring in late June 2022. He obtained a bachelor's degree in mechanical engineering and physics at Rutgers University and a master's in optical engineering at the University of Rochester. Before becoming an editor, John worked as an engineer at RCA, Exxon, Eastman Kodak, and GCA Corporation.

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