Technology: germanium single-photon detectors (Ge-on-Si SPAD) by GeQD
The Solution
Germanium-on-silicon SPADs, built for scale.
GeQD is developing a single-photon detector platform that uses germanium as the absorption material, extending sensitivity into the near-infrared and SWIR range — well beyond the reach of silicon. GeQD SPADs are built on a silicon-compatible semiconductor process, combining SWIR photon absorption with scalable manufacturing and integration with CMOS readout electronics.
Targeting visible-to-SWIR sensitivity
≈ 600 – 1550 nm
Germanium absorber for SWIR reach
One material platform across the band
Designed for room-temperature operation
No cryogenics in the target design
Avoids cryostat-bound deployment
Targeting compact, system-friendly modules
Enabling a path toward CMOS-scale integration
Silicon-compatible process
Compatible with CMOS readout
Foundation for future arrays
GeQD targets scalability, SWIR detection and system integration in one platform
Detector type
Wavelength
Cooling
Scalability
Cost
Key limitation
Silicon SPAD
Visible / NIR
Room temperature
High
Low
Weak beyond ~1 µm. Blind in SWIR.
InGaAs / InP SPAD
900–1700 nm
Often cooled / gated
Limited
Cost, integration, afterpulsing
SNSPD
Broadband
Cryogenic (~1–4 K)
Very high
Cooling & infrastructure overhead
GeQD Ge-on-Si SPAD
600–1550 nm
Room temperature Not yet demonstrated
CMOS-compatible
Low (competitive with Silicon SPADs at scale)
LabOne at TRL 4 today — TRL 5 targeted for 2027/2028
Wavelength range and CMOS compatibility are inherent properties of the Ge-on-Si platform. Cost parity with Silicon SPADs follows from CMOS processing at scale. Room-temperature operation at the targeted performance is the goal but has not yet been demonstrated; the TRL milestone is a roadmap target.
How a detection event happens
A single photon in the visible-to-SWIR range enters the detector.
Germanium absorbs the photon and converts it into an electron-hole pair.
The charge carrier is accelerated and triggers an avalanche of carriers.
Built on a silicon substrate compatible with semiconductor manufacturing flows.
Standard CMOS electronics convert the avalanche into a clean electrical pulse.
A timestamped digital event is delivered to the host system.
Simplified Ge-on-Si SPAD layer structure
Performance parameters
Characterisation of the current detector generation is ongoing. The table shows the status per parameter; measured data is shared under NDA.
Parameter
Status
Photon detection efficiency (PDE)
Characterisation in progress
Dark count rate (DCR)
Timing jitter
Afterpulsing probability
Dead time
Operating temperature
TEC-cooled demonstrators; room temperature as development target
Array scalability
Single pixels and test arrays; array scaling in development
Values will be published as characterization data is consolidated. GeQD reports parameters from internal lab measurements unless otherwise indicated.
From this platform, GeQD is developing detector modules and arrays for quantum, sensing and photonic test applications.
Germanium-on-silicon SPAD platform · room-temperature target · CMOS-compatible · 600–1550 nm
Detector flow
From photon to digital event.
Schematic of GeQD's Ge-on-Si single-photon detection.
01 Photon Incoming photon (NIR / SWIR)
02 Ge absorption Photon absorbed in germanium region
03 Charge generation Electron–hole pair created
04 Avalanche region Avalanche multiplication in Si
05 Silicon platform Multiplication on Si substrate
06 CMOS Readout circuit Quenching & front-end electronics
07 Detection pulse Digital single-photon event
In GeQD's, germanium extends photon absorption into longer wavelengths while the silicon-compatible platform supports a path toward scalable manufacturing and readout integration.
Schematic representation of a platform concept — not a finalized device geometry.
Why GeQD
How the Ge-on-Si platform compares
Feature
Ge (Ge-SPAD) Target · model-based
InGaAs SPAD
SNSPD
Si-SPAD
SWIR (>1100 nm)
✓ Target
Room temperature (target)
✓ Not yet demonstrated
partial
CMOS scalable
Industrial viable
limited
niche
limited SWIR
All GeQD entries are model-based target values from lab measurements and platform modeling. SWIR, CMOS scalability and industrial viability are achievable; room-temperature operation at sufficient performance is the goal but not yet demonstrated.
Product Roadmap
From Lab Modules to Industrial Arrays
A phased approach from first research modules to scalable industrial products.
GeQD LabOne
4-Channel SWIR SPAD Module
In development — TRL 4 · 2027 (target)
A compact single-photon detection module for quantum research and industrial prototyping.
Easy handling (Plug-and-Play)
Weight & size efficient
Integration into customer-specific applications
4-channel SWIR SPAD
Fiber-coupled, room-temperature target
VisionOne
SPAD Array Platform
In development — TRL 3
A scalable SPAD array platform for automotive LiDAR and industrial sensing applications.
High performance and scalability
Weight & size efficient for versatile system integration
Room-temperature operation (target)
Core Use Case: LiDAR
VisionOne is designed as the core detector for next-generation 1550 nm LiDAR systems. Ge-SPADs enable eye-safe operation with significantly higher range than conventional silicon detectors — at a fraction of InGaAs cost. This makes GeQD the missing piece for scalable, automotive-grade LiDAR.
Semiconductor materials for LiDAR detectors
Ge-on-Si combines SWIR sensitivity with CMOS-compatible fabrication — well suited to scalable, industrial LiDAR detectors.
Daylight
Range
GeQD range ≈ 4× of Si (model-based target — not yet demonstrated)
Rain & Fog
GeQD range ≈ 3× of Si (model-based target — not yet demonstrated)
Cost
(lower = better)
GeQD ~10× cheaper than InGaAs and close to Si (model-based projection at scale — not yet validated)
* Model-based target values derived from laboratory measurement data; not yet demonstrated in field tests.
Wavelength Advantage
Same scene, two detectors. 1550 nm Ge-SPADs return a denser point cloud and reach further than 905 nm silicon — across day, night, and adverse weather.
* Based on calculations from the laboratory demonstrator.
Eye-Safe
1550 nm is inherently eye-safe
Higher Range
Reaches further at eye-safe power
All-Weather
Better fog & rain penetration
BioSeries
Exploratory
SWIR imaging modules for medical diagnostic applications.
SWIR imaging for medical
Deep tissue detection
Time-resolved imaging
Research
Scientific Foundation
Our technology is built on peer-reviewed research in Ge-on-Si single-photon avalanche diodes.
Backside illuminated Ge-on-Si NIR camera
M. Oehme, M. Kaschel, S. Epple, M. Wanitzek, Z. Yu, D. Schwarz, A.C. Köllner et al.
IEEE Sensors Journal 21 (17), 18696–18705, 2021
Low-temperature performance of GeSn-on-Si avalanche photodiodes toward single-photon detection
M. Wanitzek, M. Hack, D. Schwarz, J. Schulze, M. Oehme
Materials Science in Semiconductor Processing 176, 108303, 2024
Ge-on-Si single-photon avalanche diode using a double mesa structure
M. Wanitzek, J. Schulze, M. Oehme
Optics Letters 49 (22), 6345–6348, 2024
GeSn-on-Si avalanche photodiodes for short-wave infrared detection
M. Wanitzek, M. Oehme, C. Spieth, D. Schwarz, L. Seidel, J. Schulze
ESSCIRC 2022 – IEEE 48th European Solid State Circuits Conference, 2022
Ge-on-Si avalanche photodiodes for LIDAR applications
M. Wanitzek, M. Oehme, D. Schwarz, K. Guguieva, J. Schulze
43rd International Convention on Information, Communication and Electronic Technology (MIPRO), 2020
GeSn‐on‐Si avalanche photodiodes with high responsivity and low dark current
M. Wanitzek, H. Ramachandra, C. Spieth, A. Daus, J. Schulze, M. Oehme
Advanced Electronic Materials 11 (21), e00495, 2025
Universität Stuttgart – Institut für Halbleitertechnik
Contact
Pfaffenwaldring 47
70569 Stuttgart, Deutschland
Tel: +49 711 68560896
info@geqd.de
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