Key Takeaways & Executive Findings
- •• A novel asymmetric PIN structure in a Ge photodetector improves electric field distribution and reduces depletion width, enhancing speed. • The device achieves high responsivity of 1.49 A/W at 1550 nm and 1.16 A/W at 1600 nm under weak avalanche at -7 V. • Bandwidths of 47.1 GHz and 44.5 GHz are obtained at 1550 nm and 1600 nm, respectively, enabling high-speed operation. • The fabrication process is simplified using a commercial 140 nm SiPH platform, making it CMOS-compatible and cost-effective.
Abstract
A silicon-based germanium (Ge) photodetector operating in the C and L bands is proposed. The device features a novel asymmetric PIN structure that optimizes the electric field distribution in Ge and reduces the effective width of the depleted region. The optical structure is carefully designed to enhance responsivity over a broad wavelength range. Under a bias of -7 V, where a weak avalanche process occurs, the device achieves responsivities of 1.49 A/W at 1550 nm and 1.16 A/W at 1600 nm, with corresponding bandwidths of 47.1 GHz and 44.5 GHz, respectively. These results demonstrate significant potential for applications in high-speed optical communication systems.
1. Introduction
The rapid advancement of data-driven technologies, such as 5G networks, artificial intelligence (AI), and the internet of things (IoT), has dramatically increased the demand for high-speed, high-capacity optical communication systems. Traditional single-wavelength transmission methods are increasingly constrained by bandwidth limitations, signal-to-noise ratio degradation, and rising power consumption. To address these challenges, wavelength-division multiplexing (WDM) technology has emerged as a cornerstone of modern optical networks. By enabling the simultaneous transmission of multiple wavelengths through a single optical fiber, WDM significantly enhances spectral efficiency and supports high-speed, long-distance communication.
Among the conventional communication bands, the C-band (1530–1565 nm) has been the industry standard due to its low transmission loss and compatibility with erbium-doped fiber amplifier (EDFA) technology. However, the exponential growth in global data traffic has necessitated exploration beyond the C-band. The L-band (1565–1625 nm) offers an attractive solution for expanding network capacity while maintaining low-loss transmission characteristics. The combined use of the C and L bands further optimizes spectral efficiency, paving the way for scalable, future-proof optical communication systems.
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Yiling Hu, Zhipeng Liu, Zhi Liu, Yupeng Zhu, Tao Men, Guangze Zhang, Jun Zheng, Yuhua Zuo, Buwen Cheng (2025). High-Responsivity and High-Speed Germanium Photodetector for C + L Band Applications. Journal of Semiconductors (半导体学报 - 中国科学院半导体研究所). https://doi.org/10.1088/1674-4926/25030017
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Frequently Asked Questions
What is the operating wavelength range of the proposed germanium photodetector?
The photodetector is designed for the C and L bands, covering 1530–1625 nm, with specific performance demonstrated at 1550 nm and 1600 nm.
How does the asymmetric PIN structure improve device performance?
The asymmetric PIN structure optimizes the electric field distribution in the germanium absorption region and reduces the effective width of the depleted region, thereby decreasing carrier transit time and enhancing speed.
What are the key performance metrics at -7 V bias?
At -7 V, the device achieves responsivities of 1.49 A/W at 1550 nm and 1.16 A/W at 1600 nm, with bandwidths of 47.1 GHz and 44.5 GHz, respectively.
What is the significance of the weak avalanche effect in this device?
The weak avalanche effect provides moderate internal gain to enhance responsivity while maintaining low excess noise, making the device suitable for high-sensitivity optical receivers.
Is the fabrication process CMOS-compatible?
Yes, the device is fabricated on a SOI substrate using a commercial 140 nm SiPH platform with a simple CMOS-compatible process, ensuring cost-effectiveness and scalability.
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