A photodiode helps transfer data between servers in AI data centres at 400 Gbps while improving signal strength and reducing power use.
Imec has developed a germanium/silicon (Ge/Si) avalanche photodiode (APD) with a bandwidth of 100 GHz, a 5 V operating voltage and a responsivity of 1.8 A/W across both the O- and C-bands. The device improves receiver sensitivity by 3 dB and was used to demonstrate the first net 400 Gbps optical link with an APD receiver. The technology targets optical interconnects for AI data centres, where data must move quickly between servers while reducing energy consumption.
As AI workloads grow, data centres need optical links that transfer large volumes of data between racks and blade servers at low latency and higher data rates per lane. To support this demand, imec is developing silicon photonics components, including high-speed modulators and photodetectors, for next-generation optical interconnects.
Imec has also developed a germanium/silicon electro-absorption modulator (EAM) operating beyond 110 GHz in the C-band. This component supports the transmitter side of short-reach optical links used to connect computing resources. On the receiver side, photodetectors must provide high sensitivity while supporting increasing bandwidths.
Avalanche photodiodes address this challenge through internal signal amplification, which improves receiver sensitivity. However, conventional designs have often required a trade-off between bandwidth, operating voltage and amplification. Imec’s new device combines 100 GHz bandwidth with 5 V operation and high responsivity, addressing these limitations for high-speed optical communication.
“The team started from the well-established SACM (separate absorption, charge and multiplication) APD architecture, but re-engineered the device at its core,” said Joris Van Campenhout, VP R&D Optical Interconnects at imec. “By scaling the multiplication layer width to below 100 nm – leveraging a deeply recessed germanium-in-silicon structure – and eliminating the charge layer, we were able to simultaneously achieve 100 GHz bandwidth, 5 V operation and a responsivity of 1.8 A/W, corresponding to approximately a twofold internal gain.”
