imec demonstrates 100 GHz Ge/Si APD
New APD enables net 400 Gbps optical link on 300 mm silicon photonics platform.
imec has demonstrated a 100 GHz germanium-on-silicon (Ge/Si) avalanche photodiode (APD) designed for next-generation optical interconnects in AI data centres.
Presented at ECOC 2026, the device combines 100 GHz bandwidth, 5 V operation and a responsivity of 1.8 A/W across both the O- and C-bands. Imec said the APD provides approximately twofold internal gain and delivers a 3 dB improvement in receiver sensitivity compared with a conventional photodiode.
The device was manufactured on imec's 300 mm silicon photonics platform. Its performance was demonstrated at system level by combining the APD with imec's previously demonstrated beyond-110 GHz C-band Ge/Si electro-absorption modulator (EAM), enabling what imec describes as the first net 400 Gbps optical link employing an APD receiver.
The APD uses a modified separate absorption, charge and multiplication architecture. Imec reduced the multiplication layer to below 100 nm using a deeply recessed germanium-in-silicon structure and eliminated the charge layer, allowing the device to achieve high bandwidth while operating at a relatively low voltage.
The resulting receiver sensitivity improvement could either allow lower laser power or provide additional margin for optical losses, according to imec.
“The APD provides additional link margin compared with a conventional photodiode,” said Joris Van Campenhout, VP R&D Optical Interconnects at imec. “Combined with its high bandwidth and low operating voltage, this makes the device particularly attractive for future scale-up optical interconnects.”
imec will next focus on improving reliability across different temperatures and optical input power conditions, as well as integrating the APD with high-speed receiver electronics. The company will continue developing the technology on its 300 mm silicon photonics platform.
