Key Takeaways & Executive Findings
- •• A novel asymmetric PIN structure optimizes electric field distribution and reduces effective depletion width, enhancing speed. • The photodetector achieves high responsivity of 1.49 A/W at 1550 nm and 1.16 A/W at 1600 nm under -7 V bias. • Bandwidths of 47.1 GHz at 1550 nm and 44.5 GHz at 1600 nm are demonstrated, suitable for high-speed C+L band operation. • The device shows significant potential for next-generation optical communication systems requiring broad bandwidth and high sensitivity.
Abstract
A silicon-based germanium (Ge) photodetector working for C and L bands is proposed in this paper. The device features a novel asymmetric PIN structure, which contributes to a more optimized electric field distribution in Ge and a shorter effective width of depleted region. Meanwhile, the optical structure is designed carefully to enhance responsivity for broadband. Under −7 V, where the weak avalanche process happens, the responsivity of our device is 1.49 and 1.16 A/W at 1550 and 1600 nm, with bandwidth of 47.1 and 44.5 GHz, respectively. These performances demonstrate the significant application potential of the device in 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.
In parallel, silicon photonics has revolutionized optical communication by leveraging CMOS-compatible fabrication techniques to produce compact, cost-effective photonic devices. Among these devices, silicon-based germanium (Ge) photodetectors have emerged as key components due to their superior optical absorption in the near-infrared region and seamless integration with silicon platforms.
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HU Yiling, LIU Zhipeng, LIU Zhi, ZHU Yupeng, MEN Tao, ZHANG Guangze, ZHENG Jun, ZUO Yuhua, CHENG Buwen (2025). High-responsivity and high-speed germanium photodetector for C + L application. SinoTechIntel Verified Research. 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 C and L bands, covering 1530–1625 nm, with specific performance demonstrated at 1550 nm and 1600 nm.
What are the key performance metrics of the photodetector?
Under -7 V bias, 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.
How does the asymmetric PIN structure improve device performance?
The asymmetric PIN structure optimizes the electric field distribution in germanium and shortens the effective width of the depleted region, leading to faster carrier transit and higher bandwidth.
What is the significance of this photodetector for optical communication?
It offers high responsivity and high speed across C and L bands, making it suitable for wavelength-division multiplexing systems to expand capacity and support high-speed data transmission.
Is the photodetector compatible with CMOS fabrication?
Yes, it is silicon-based and leverages CMOS-compatible fabrication techniques, enabling cost-effective integration with silicon photonics platforms.
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