Graphene photodetectors with a bandwidth  >76 GHz fabricated in a 6″ wafer process line

Abstract

In recent years, the data traffic has grown exponentially and the forecasts indicate a huge market that could be addressed by communication infrastructure and service providers. However, the processing capacity, space, and energy consumption of the available technology is a serious bottleneck for the exploitation of these markets. Chip-integrated optical communication systems hold the promise of significantly improving these issues related to the current technology. At the moment, the answer to the question which material is best suited for ultrafast chip integrated communication systems is still open. In this manuscript we report on ultrafast graphene photodetectors with a bandwidth of more than 76 GHz well suitable for communication links faster than 100 GBit/s per channel. We extract an upper value of 7.2 ps for the timescale in which the bolometric photoresponse in graphene is generated. The photodetectors were fabricated on 6" silicon-on-insulator wafers in a semiconductor pilot line, demonstrating the scalable fabrication of high-performance graphene based devices.Optical communication in general and especially chip integration of optic and electronic components has been considered as a promising way to significantly increase the performance of datalinks in terms of capacity, energy consumption, and costs [1][2][3]. The current bottleneck that hinders the mass production of chip integrated electro-optic components like modulators and photodetectors is the lack of a material that is compatible to established processing technology of chips while giving high performance devices. The electronic and optic properties of graphene [4], the two dimensional allotrope of carbon, were studied extensively in the last years [5][6][7][8][9]. Moreover, competitive chipintegrated electro-optical devices like electro-optical modulators [10,11], efficient waveguide heaters [12] and ultrafast photodetectors [13][14][15][16] were fabricated using graphene as active material. The performance of graphene photodetectors on integrated silicon waveguides in terms of speed and sensitivity has improved significantly in the last years and the gap between the performance of graphene and competing technologies is vanishing [17][18][19][20][21]. The possible monolithic integration on various substrates that are not necessarily crystalline is a key merit that distinguishes graphene from Ge or III/V materials. The bandwidth reported for graphene photodetectors of up to 65 GHz [16] and sensitivity around 0.4 A/W without bias and 1 A/W with bias [22] underline the potential of graphene for chip integrated photodetectors. Besides an excellent device performance the integration in a large scale production environment is essential. However, the introduction of new materials into an existing fabrication process flow and the required adoption as well as development of entirely new process steps are among the most challenging tasks in the fabrication of integrated circuits. So far, graphene photodetectors on silicon waveguides were fabrica...

Ultra-compact integrated graphene plasmonic photodetector with bandwidth above 110 GHz

“…EQE Bandwidth Type of graphene [12] 100 mA/W 7.9% 20 GHz Exfoliation [15] 7 mA/W 0.56% 41 GHz CVD [39] 57 mA/W 4.56% 3 GHz CVD [28] 360 mA/W 29% 42 GHz Exfoliation [17] 76 mA/W 6.4% 65 GHz Exfoliation [18] 370 mA/W 29.5% --CVD [29] 1 mA/W 0.08% 76 GHz CVD (*) [35] 500 mA/W 40% 100 GHz --This work 360 mA/W 29% >110 GHz CVD plasmonic slot waveguide hybrid structure. The narrow plasmonic slot waveguide not only enhances light-graphene interactions, but also enables to separate the photo-generated carriers effectively, leading to high responsivity and large bandwidth.…”

High-performance silicon−graphene hybrid plasmonic waveguide photodetectors beyond 1.55 μm

“…For example, silicon-graphene waveguide photodetectors operating at 1.55 μm were realized with a bandwidth of >76 GHz successfully in a 6-inch wafer process line 20 . More recently silicon-graphene waveguide photodetectors working at 1.55 μm were reported with a bandwidth even as high as 100…”

Spatially controlled electrostatic doping in graphene p-i-n junction for hybrid silicon photodiode

“…Compared to other G photodetectors, the PTI effect in vertical junction, in combination with low noise carrier transportation along the lateral p-i-n junction, lead to the highest SNR (Table 1) with zero bias operation. Higher responsivity and operation speed can be easily achieved in other structures, as the photothermal or bolometric effect leads to light intensity dependent resistance change in G. However, the on-off ratio stays poor without effective separation of carriers [28,36]. In the visible wavelength, the G-Si p-i-n heterojunction demonstrated a much higher efficiency comparing with the G-WSe2 heterojunction (70%) [27] and G-Si heterojunction (65%) [60].…”