Ultra-fast germanium photodiode with 3-dB bandwidth of 265 GHz

Abstract

On a scalable silicon technology platform, we demonstrate photodetectors matching or even surpassing state-of-the-art III–V devices. As key components in high-speed optoelectronics, photodetectors with bandwidths greater than 100 GHz have been a topic of intense research for several decades. Solely InP-based detectors could satisfy the highest performance specifications. Devices based on other materials, such as germanium-on-silicon devices, used to lag behind in speed, but enabled complex photonic integrated circuits and co-integration with silicon electronics. Here we demonstrate waveguide-coupled germanium photodiodes with optoelectrical 3-dB bandwidths of 265 GHz and 240 GHz at a photocurrent of 1 mA. This outstanding performance is achieved by a novel device concept in which a germanium fin is sandwiched between complementary in situ-doped silicon layers. Our photodetectors show internal responsivities of 0.3 A W−1 (265 GHz) and 0.45 A W−1 (240 GHz) at a wavelength of 1,550 nm. The internal bandwidth–efficiency product of the latter device is 86 GHz. Low dark currents of 100–200 nA are obtained from these ultra-fast photodetectors.

Metamaterial-enabled arbitrary on-chip spatial mode manipulation

“…Moreover, once the multimode fiber-to-chip coupling techniques are improved in the future, the metamaterial-enabled arbitrary mode manipulation can play an important role in further combining the application scenarios of long-distance information transmission and on-chip data transmission together. It is worth mentioning that all necessary components for coherent communications have been demonstrated on integrated platforms, including narrow-linewidth laser sources 43 , high-speed in-phase/quadrature modulators (IQM) 44 , and high-speed photodetectors 45 . Besides, integrated coherent receiver 46 and transmitters 47 have also been experimentally reported.…”

Optical Interconnects Finally Seeing the Light in Silicon Photonics: Past the Hype

“…The efforts to build p-i-p photodetectors that utilized the avalanche effect to achieve a quantum efficiency larger than 100% were also surveyed. Recent interesting research stands out for being able to achieve an ultra-high bandwidth of 265 GHz with a low dark current (100 nA) and a high responsivity of 0.3 A/W, hence outperforming the most sophisticated InP photodetectors in terms of its high-speed performance, while being made from Ge and silicon, making it more suitable for the integration with electronics circuits [196]. A summary of the complete interconnect systems built by academia and the industry was presented and showed speeds ranging from 20 Gbps to 80 Gbps and energy consumption from 50 pJ/bit down to 1 pJ/bit.…”

“…A detailed review of the recent advances in photodetector research for the infrared spectrum was given by Chen et al [206]. Recent interesting research stands out for being able to achieve a ultra-high bandwidth of 265 GHz with a low dark current of 100 nA and a high responsivity of 0.3 A/W, hence outperforming most sophisticated InP photodetectors in terms of high-speed performance, while being made from Ge and silicon, making it more suitable for integration with electronics circuits [196].…”

Graphene on Silicon Photonics: Light Modulation and Detection for Cutting-Edge Communication Technologies

“…Ge-Si hybrid photodetectors have been widely studied and reached significant maturity thanks to their ability to absorb light in the telecommunications band near 1550 nm. High responsivity larger than 1 A/W has been achieved and an impressive bandwidth of 265 GHz has been demonstrated recently [53,55]. Compared to Ge/Si photodetectors, graphene/Si photodetectors hold great potential in reaching ultra large operation bandwidth thanks to the ultrahigh carrier mobility of graphene as well as its absorption ability in a broader wavelength range.…”

“…The PV effect relies on the separation of photoexcited electrons and holes by an applied electric field to generate photocurrent, which can be utilized by graphene/silicon photodetector structures with normal light incidence [53,54]. As the representative work of early endeavors in graphene-based photodetectors, Xia et al demonstrated that the graphene/Si photodetectors can reach 40 GHz [55]. Moreover, the intrinsic response time of graphene photodetectors is experimentally demonstrated to be 2.1 ps, indicating a high bandwidth of 262 GHz (Figure 3a) [56].…”