Ge-on-Si SPADs vs. SNSPDs — the technical comparison
SNSPDs deliver the highest performance for SWIR single-photon detection today — but they require cryogenic infrastructure. Ge-on-Si SPADs target a different front: semiconductor manufacturing, room-temperature operation as a goal, and scalability. Here is a sober comparison of the trade-offs.
TL;DR
• SNSPDs: best detection efficiency and timing resolution in the SWIR — at the cost of cryogenics (≈ 0.8–4 K), helium infrastructure, and six-figure system cost.
• Ge-on-Si SPADs: semiconductor process on 200/300 mm wafers, CMOS-compatible, room temperature as a target, far lower per-unit cost at scale.
• The right choice depends on the use case: lab/research with top specs → SNSPD. Volume, field deployment, integration → Ge-on-Si.
Operating temperature Not yet demonstrated
Cryogenics dominates the footprint, power draw, and maintenance of SNSPD systems.
Fabrication & scalability
CMOS compatibility unlocks existing foundry capacity and array integration.
System cost
Compare total cost of ownership including He consumption and service.
Performance (SWIR, 1310–1550 nm) Target · model-based
Ge-on-Si is not aimed at SNSPD record specs — but at the best industrially deployable level.
Wavelength range
Ge intrinsically absorbs out to 1550 nm — no exotic material stacks needed.
Integration
Relevant for QKD receivers, LiDAR detector arrays, imaging SWIR sensors.
Which technology fits which use case?
Bottom line
SNSPDs set today's performance standard. Ge-on-Si SPADs pull a different lever: semiconductor manufacturing, room temperature as a target, and unit cost that opens up volume applications. The two technologies don't compete head-on so much as they serve different market segments.
More on GeQD technology
A deeper look at our detector architecture, prototypes, and roadmap.
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