arxiv: 2605.07343 · v1 · submitted 2026-05-08 · ⚛️ physics.ins-det

Recognition: no theorem link

Review of germanium-silicon single-photon avalanche diodes

Erik Chen, Gerald S. Bullerb, Neil Na, Richard A. Sorefd, Robert H. Hadfield

Authors on Pith no claims yet

Pith reviewed 2026-05-11 01:13 UTC · model grok-4.3

classification ⚛️ physics.ins-det

keywords germanium-siliconsingle-photon avalanche diodeshortwave infraredsingle-photon detectionSPADroom temperaturecryogenic demonstrationoptical sensing

0 comments

The pith

Germanium-silicon SPADs have advanced from cryogenic to room-temperature single-photon detection in the shortwave infrared.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper reviews the development of germanium-silicon single-photon avalanche diodes for detecting individual photons in the shortwave infrared. It follows the technology from its first demonstration at cryogenic temperatures in 2011 through to a room-temperature demonstration in 2024. A sympathetic reader would care because removing the need for cooling systems makes these detectors far more practical for everyday use. The review also points to potential new applications in active optical sensing and imaging that become possible with this capability.

Core claim

The authors establish that GeSi SPADs have reached the point where single-photon avalanche detection works at room temperature in the SWIR band after more than a decade of refinement from early cryogenic devices. This review lays out the sequence of demonstrations and material improvements that produced the shift. It positions the devices for broader use in sensing and imaging beyond their initial high-speed communication role.

What carries the argument

The germanium-silicon heterostructure single-photon avalanche diode, which absorbs SWIR photons in the germanium layer and triggers avalanche multiplication for detection.

If this is right

Room-temperature operation removes the requirement for cryogenic cooling hardware.
The devices become suitable for compact systems in active optical sensing and imaging.
New applications in shortwave infrared detection can be explored without specialized cooling infrastructure.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

Integration of these diodes with standard silicon circuits could produce compact, low-cost sensor arrays.
The technology might support applications such as eye-safe lidar or biomedical imaging where cooling is undesirable.
Further material refinements could extend the operating range or improve timing resolution for quantum-related uses.

Load-bearing premise

The performance numbers and dates reported in the cited prior experiments, including the 2024 room-temperature result, are accurate.

What would settle it

An independent measurement showing that the reported 2024 room-temperature GeSi SPAD fails to detect single photons at the claimed efficiency and noise levels would undermine the review's timeline of progress.

Figures

Figures reproduced from arXiv: 2605.07343 by Erik Chen, Gerald S. Bullerb, Neil Na, Richard A. Sorefd, Robert H. Hadfield.

**Figure 4.** Figure 4: (a) Top view and the cross-sectional schematics of the structure used for Ge LPE growth. The seeding region is expected to be defective due to the lattice mismatch between Ge and Si, but the dislocations grow along the crystallographic planes and terminate quickly. (b) SEM image of the LPE Ge on Si nitride with the seeding window on the Si substrate. Figures reproduced with permission from Ref. [11] AIP. I… view at source ↗

**Figure 5.** Figure 5: (a) The structure of the Ge PD. (b) Eye diagrams at 4.25 Gb/s and -12 dBm for receivers containing a GaAs PD (left) and Ge PD (right). The jitters of the two receivers are similar and well within the specification for commercial receivers. Figures reproduced with permission from Ref. [13] IEEE. Normal-incidence GeSi APD In the same year 2009, Intel [14] first demonstrated a Ge/Si (abbreviated as GeSi in th… view at source ↗

**Figure 6.** Figure 6: (a) The structure of the GeSi APD. (b) Back [PITH_FULL_IMAGE:figures/full_fig_p005_6.png] view at source ↗

**Figure 8.** Figure 8: (a) The structure of the GeSi SPAD in Ref. [16]. (b) SPDE and DCR at 78 K (left), 100 K (middle), and 125 K [PITH_FULL_IMAGE:figures/full_fig_p007_8.png] view at source ↗

**Figure 9.** Figure 9: (a) The structure of the GeSi SPAD in Ref. [17]. (b) DCR (left) and SPDP (right) at 300 K. Figures reproduced with [PITH_FULL_IMAGE:figures/full_fig_p008_9.png] view at source ↗

**Figure 10.** Figure 10: (a) Schematic plot of a room-temperature PQC paradigm with integrated SiPh using the path degree of freedom of single photons: single photons are generated through SFWM (green pulses converted to blue and red pulses) in SOI rings (orange circles), followed by active temporal multiplexers (orange boxes that block the blue pulses), and active spatial multiplexers (orange boxes that convert serial pulses to … view at source ↗

read the original abstract

While it took about a decade for a germanium (Ge) thin film grown on a silicon (Si) substrate to be successfully applied as a detector material for high-speed optical fiber communication application, it took about another decade to further expand its usage as a sensor material for active optical sensing and imaging applications. In this paper, we shall review the progress of a shortwave infrared (SWIR) single-photon detection (SPD) with germanium-silicon (GeSi) single-photon avalanche diode (SPAD), ranging from the first demonstration at cryogenic temperature (Z. Lu et al., 2011) to the recent demonstration at room temperature (N. Na et al, 2024). Potential new applications will also be discussed.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

This is a basic review that lines up the GeSi SPAD timeline from 2011 cryogenic work to the 2024 room-temp result, with no new data or analysis.

read the letter

The main point is that this paper is a review summarizing the history of germanium-silicon single-photon avalanche diodes for shortwave infrared single-photon detection. It walks through the demonstrations from the first cryogenic result in 2011 up to the authors' own room-temperature work in 2024 and mentions some possible applications. That chronological summary is what it offers, and it does pull the scattered references into one document, which can be convenient for someone starting in this narrow area of SWIR detectors. The citations appear to be handled straightforwardly without obvious invention of new claims. Nothing original is added in terms of measurements, models, or first-principles work, so the contribution stays at the level of consolidation. The soft spots are the usual ones for a review: its accuracy depends entirely on how faithfully the cited papers are represented, including the authors' recent demonstration. The abstract gives no sign of major gaps or overemphasis, but a referee would still need to verify completeness and balance. There are no equations, derivations, or fitted results to check, which removes the usual concerns about hidden assumptions or circularity. This is aimed at specialists already working on single-photon detectors or SWIR sensing who want a quick reference to the development sequence. A broader audience in optics or instrumentation would likely find it too narrow. It is the sort of review that belongs in a specialized journal and deserves peer review to confirm the coverage of the literature. I would send it out rather than desk reject, with the expectation that referees focus on whether the timeline and citations are complete and even-handed.

Referee Report

0 major / 2 minor

Summary. The manuscript is a review that summarizes the development of germanium-silicon single-photon avalanche diodes (GeSi SPADs) for shortwave infrared single-photon detection. It covers the timeline from the first cryogenic-temperature demonstration (Z. Lu et al., 2011) to the recent room-temperature demonstration (N. Na et al., 2024) and discusses potential applications in active optical sensing and imaging.

Significance. If the cited literature is represented accurately, the review provides a consolidated chronological account of progress in GeSi SPAD technology for SWIR applications. This could be a convenient reference for the detector community by highlighting the shift toward practical room-temperature devices, though the paper introduces no new data, derivations, or quantitative synthesis.

minor comments (2)

Abstract: the citation format 'N. Na et al, 2024' is inconsistent with standard bibliographic style; ensure all in-text citations match the reference list exactly.
The review would benefit from a concise table (perhaps in a new section after the timeline) that tabulates key metrics such as detection efficiency, dark-count rate, and operating temperature for each cited demonstration; this would improve clarity without altering the narrative structure.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for their review of our manuscript. The referee's summary accurately reflects the content of our review, which provides a chronological overview of GeSi SPAD development for SWIR single-photon detection from the 2011 cryogenic demonstration to the 2024 room-temperature results, along with discussion of applications. We note the recommendation for minor revision but observe that no specific major comments were raised.

Circularity Check

0 steps flagged

No significant circularity in review summary

full rationale

This is a pure review paper that chronologically summarizes prior publications on GeSi SPAD development without advancing any original derivations, equations, fitted parameters, predictions, or theoretical claims. The narrative simply reproduces reported timelines, temperatures, and metrics from cited works (including the authors' own 2024 result) under the standard assumption that those citations are accurate. No self-definitional loops, fitted-input predictions, or load-bearing self-citations that reduce the central claim to its own inputs exist; the structure is narrative citation summary rather than synthesis that could introduce circularity.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

This is a review paper. It introduces no free parameters, axioms, or invented entities; all technical content is drawn from previously published work.

pith-pipeline@v0.9.0 · 5427 in / 1063 out tokens · 34592 ms · 2026-05-11T01:13:22.696432+00:00 · methodology

discussion (0)

Reference graph

Works this paper leans on

21 extracted references · 21 canonical work pages

[1]

High-performance Ge-on-Si photodetectors

J. Michel, J. Liu, and L. C. Kimerling, "High-performance Ge-on-Si photodetectors", Nat. Photon 4, 527 (2010)

work page 2010
[2]

Demonstration of a High Speed 4 -Channel Integrated Silicon Photonics WDM Link with Hybrid Silicon Lasers,

A. Alduino et al., "Demonstration of a High Speed 4 -Channel Integrated Silicon Photonics WDM Link with Hybrid Silicon Lasers, " in Integrated Photonics Research, Silicon and Nanophotonics and Photonics in Switching , OSA Technical Digest (CD) (Optica Publishing Group, 2010), paper PDIWI5

work page 2010
[3]

A 4×12.5 Gb/s CWDM Si photonics link using integrated hybrid silicon lasers ,

B. Koch et al., "A 4×12.5 Gb/s CWDM Si photonics link using integrated hybrid silicon lasers ," in CLEO:2011 - Laser Applications to Photonic Applications , OSA Technical Digest (CD) (Optica Publishing Group, 2011), paper CThP5

work page 2011
[4]

A Grating-Coupler-Enabled CMOS Photonics Platform,

A. Mekis et al., "A Grating-Coupler-Enabled CMOS Photonics Platform," IEEE J. Sel. Top. Quant. Electron. 17, 597 (2011)

work page 2011
[5]

Bulk-Si photonics technology for DRAM interface,

H. Byun et al., "Bulk-Si photonics technology for DRAM interface," Photon. Res. 2, A25 (2014)

work page 2014
[6]

High-Performance Germanium -an-Silicon Lock-in Pixels for Indirect Time -of-Flight Applications,

N. Na et al., "High-Performance Germanium -an-Silicon Lock-in Pixels for Indirect Time -of-Flight Applications, " 2018 IEEE International Electron Devices Meeting (IEDM), San Francisco, CA, USA, 2018, pp. 32.4.1-32.4.4

work page 2018
[7]

An Up-to-1400nm 500MHz Demodulated Time-of-Flight Image Sensor on a Ge-on-Si Platform,

C.-L. Chen et al., "An Up-to-1400nm 500MHz Demodulated Time-of-Flight Image Sensor on a Ge-on-Si Platform," 2020 IEEE International Solid-State Circuits Conference (ISSCC), San Francisco, CA, USA, 2020, pp. 98-100

work page 2020
[8]

Single-photon detection for long range imaging and sensing,

R. H. Hadfield et al., "Single-photon detection for long range imaging and sensing," Optica 10, 1124 (2023)

work page 2023
[9]

High-quality Ge epilayers on Si with low threading -dislocation densities,

H.-C. Luan et al. , "High-quality Ge epilayers on Si with low threading -dislocation densities," Appl. Phs. Lett. 75, 2909 (1999). Proc. of SPIE Vol. 13448 1344808-9

work page 1999
[10]

High quality Ge on Si by epitaxial necking,

T. A. Langdo et al., "High quality Ge on Si by epitaxial necking," Appl. Phys. Lett. 76, 3700 (2000)

work page 2000
[11]

High -quality single-crystal Ge on insulator by liquid -phase epitaxy on Si substrates,

Y. Liu, M. D. Deal, and J . D. Plummer, "High -quality single-crystal Ge on insulator by liquid -phase epitaxy on Si substrates," Appl. Phys. Lett. 84, 2563 (2004)

work page 2004
[12]

Defects reduction of Ge epitaxial film in a germanium -on-insulator wafer by annealing in oxygen ambient,

K. H. Lee et al. "Defects reduction of Ge epitaxial film in a germanium -on-insulator wafer by annealing in oxygen ambient," APL Mater. 3, 016102 (2015)

work page 2015
[13]

Performance of Ge -on-Si p -i-n Photodetectors for Standard Receiver Modules,

M. Morse et al. "Performance of Ge -on-Si p -i-n Photodetectors for Standard Receiver Modules," IEEE Photon. Technol. Lett. 18, 2442 (2006)

work page 2006
[14]

Monolithic germanium/silicon avalanche photodiodes with 340 GHz gain –bandwidth product,

Y. Kang et al. "Monolithic germanium/silicon avalanche photodiodes with 340 GHz gain –bandwidth product," Nat. Photon. 3, 59 (2009)

work page 2009
[15]

Geiger-Mode Operation of Ge-on-Si Avalanche Photodiodes,

Z. Lu et al., "Geiger-Mode Operation of Ge-on-Si Avalanche Photodiodes," J. Sel. Quant. Electron. 47, 731 (2011)

work page 2011
[16]

High performance planar germanium -on-silicon single -photon avalanche diode detectors,

P. Vines et al., "High performance planar germanium -on-silicon single -photon avalanche diode detectors," Nat. Commun. 10, 1086 (2019)

work page 2019
[17]

Room temperature operation of germanium –silicon single-photon avalanche diode,

N. Na e t al., "Room temperature operation of germanium –silicon single-photon avalanche diode," Nature 627, 295 (2024)

work page 2024
[18]

Nature641(8064), 876–883 (2025) https:// doi.org/10.1038/s41586-025-08820-7

PsiQuantum Team , "A manufacturable platform for photonic quantum computing ," Nature (2025). https://doi.org/10.1038/s41586-025-08820-7

work page doi:10.1038/s41586-025-08820-7 2025
[19]

Room-temperature photonic quantum computing in integrated silicon photonics with germanium–silicon single-photon avalanche diodes,

N. N et al., "Room-temperature photonic quantum computing in integrated silicon photonics with germanium–silicon single-photon avalanche diodes," APL Quant. 1, 036123-1 (2024)

work page 2024
[20]

High-speed and high -efficiency travelling wave single -photon detectors embedded in nanophotonic circuits,

W. H. P. Pernice et al., "High-speed and high -efficiency travelling wave single -photon detectors embedded in nanophotonic circuits," Nat. Commun. 3, 1325 (2012)

work page 2012
[21]

Low-temperature performance of GeSn -on-Si avalanche photodiodes toward single -photon detection,

M. Wanitzek et al., "Low-temperature performance of GeSn -on-Si avalanche photodiodes toward single -photon detection," Mat. Sci. Semicon. Proc. 176, 108303 (2024). Proc. of SPIE Vol. 13448 1344808-10

work page 2024