−1 V bias 67 GHz bandwidth Si-contacted germanium waveguide p-i-n photodetector for optical links at 56 Gbps and beyond

Abstract

Abstract:We demonstrate a 67 GHz bandwidth silicon-contacted germanium waveguide p-i-n photodetector operating at -1 V with 6.8 fF capacitance. The dark current is below 4 nA. The responsivity is 0.74 A/W at 1550 nm and 0.93 A/W at 1310 nm wavelength. 56 Gbps on-off-keying data reception is demonstrated with clear open eye diagrams in both the Cband and O-band.

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

“…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.…”

100-Gbps RZ Data Reception in 67-GHz Si-Contacted Germanium Waveguide p-i-n Photodetectors

“…the RF power delivered by the photodetector to a 50 Ω load drops by a factor of 2 at 60 GHz and above) at 1550 nm as seen in Fig. 3 (reproduced from [16]). Such a high bandwidth should allow 100 Gbps on-off keying data reception as will be discussed in the subsequent sections.…”

“…The conclusion that the opto-electrical bandwidth of the 14 µm long Si-LPIN GePD is limited by the transit-time and that the responsivity in the C-band (0.74 A/W at 1550 nm) is partly limited by the short device length was drawn in [16]. This indicates that the responsivity of the 14 µm Si-LPIN GePD in the C-band can be improved by increasing the length of the device without compromising on the opto-electrical bandwidth.…”

“…The measured responsivity at -1 V bias was 0.74 A/W at 1550 nm. The dark current was as low as 4 nA at -1 V. 56 Gbps on-off keying non-return-to-zero data reception was demonstrated with clear open eye diagrams at 1550 nm at -1 V bias [16].…”

“…In [15], [16] we demonstrated that by adopting a 160 nm thick Ge layer to reduce the transit time, the opto-electrical 3-dB bandwidth at -1 V bias was enhanced to 67 GHz at 1550 nm for a 14 µm long Si-LPIN GePD. The junction capacitance was 6.8 fF at -1 V. Light coupling from the silicon-oninsulator (SOI) waveguide to the Ge waveguide was optimized by adding a poly-Si taper on top of the fully etched Si taper as shown in Fig.…”