High-Performance Self-Powered Photoelectrochemical Detection Using Scalable InGaN/GaN Nanowire Arrays

Christy Giji Jenson; Dipon Kumar Ghosh; Kishan Lal Kumawat; Md. Afjalur Rahman; Md. Moinul Islam; Md Zunaid Baten; Nirmal Anand; Samuel Olakunle Adigbo; Sharif Md. Sadaf; Sheik Munim Hussain

REVIEW 5 major objections 5 minor 15 references

High-Performance Self-Powered Photoelectrochemical Detection Using Scalable InGaN/GaN Nanowire Arrays

T0 review · 5 major / 5 minor · reviewed 2026-08-06 · deepseek-v4-flash

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Pith's one-line read This paper claims that green-emitting InGaN/GaN nanowire arrays, made by a scalable silica-nanosphere top-down etch, act as self-powered photoelectrochemical photodetectors with a record III-nitride responsivity of 330 mA/W at 365 nm.

desk verdict The reported record responsivity is numerically inconsistent with the paper's own photocurrent density and power-law fit, so the central claim doesn't hold as written. read the letter →

arxiv 2507.06501 v1 pith:CUYJB2EN submitted 2025-07-09 physics.app-ph

Kishan Lal Kumawat , Md. Afjalur Rahman , Nirmal Anand , Dipon Kumar Ghosh , Christy Giji Jenson , Md. Moinul Islam , Samuel Olakunle Adigbo , Sheik Munim Hussain

show 2 more authors

Md Zunaid Baten Sharif Md. Sadaf

This is my paper · ORCID

classification physics.app-ph

keywords III-nitridesnanowiresMQWheterostructuresself-poweredphotoelectrochemicalphotodetectorInGaN/GaNtop-downnanofabricationUVphotodetection

verification ladder T0 review T1 audit T2 compute T3 formal

The pith

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

The reading

The paper reports the first self-powered photoelectrochemical photodetector built from InGaN/GaN multiple-quantum-well nanowire arrays fabricated by a scalable top-down silica-nanosphere lithography rather than bottom-up growth. It claims a peak UV responsivity of 330 mA/W (0.33 A/W) at 365 nm and 0.7 mW/cm² illumination, which it identifies as the highest reported among III-nitride PEC photodetectors, plus a detectivity near 2.7×$10^{10}$ Jones and response/recovery times of 168/69 ms. The nanowire geometry is said to roughly double the photocurrent density (16 mA/cm² at 43.5 mW/cm²) relative to the same MQW stack in planar form by enlarging the solid-liquid interface and shortening carrier paths. If true, this makes scalable, self-powered UV-visible detection more accessible for IoT, environmental monitoring, and optical communication.

What carries the argument

The carrying object is the nanowire-array electrode: roughly 330-nm-diameter, 900-nm-tall InGaN/GaN multiple-quantum-well (MQW) nanowires fabricated by silica-nanosphere lithography plus dry and wet etching, immersed in 1 M NaOH in a three-electrode cell. The mechanism that carries the photoresponse is the built-in electric field and upward band bending at the nanowire/electrolyte interface, which separates photogenerated electron-hole pairs and sends holes to the surface for oxidation while electrons flow through the external circuit. The paper attributes the factor-of-two photocurrent gain over planar photoelectrodes to the nanowires' large solid-liquid interfacial area, reduced carrier diffusion path, and light-trapping anti-reflection effect. A coupled finite-difference time-domain optical simulation and drift-diffusion transport calculation reproduces the spectral trend of the responsivity.

What would settle it

Re-measure the same device with a calibrated aperture that defines the illuminated area and a calibrated reference photodiode, computing R = (I_light - I_dark)/(P·A) with A fixed by the aperture; if the true area is larger than the value implied here, the responsivity drops below the claimed III-nitride record.

Watch

Extended reading notes

Core claim

On the paper's own terms, the central discovery is that a top-down-etched nanowire form of an InGaN/GaN multiple-quantum-well heterostructure converts the semiconductor-electrolyte junction into a high-performance self-powered photoelectrochemical photodetector, whereas the same heterostructure as a planar photoelectrode is markedly weaker. The authors report that at 365 nm, 43.5 mW/cm², and zero applied bias, the photocurrent density reaches about 16 mA/cm², twice the planar value. At the lower intensity of 0.7 mW/cm², the responsivity reaches about 330 mA/W with a detectivity of 2.67×$10^{10}$ Jones, both decreasing as light intensity rises. The spectral response peaks at 365 nm, extends into the visible, and shows a UV/visible rejection ratio of 388. These metrics are claimed to be the highest among III-nitride PEC photodetectors reported so far.

Load-bearing premise

The 330 mA/W record depends on knowing exactly which area of the sample produced the measured current, and the paper never states or calibrates that area.

Editorial extensions

If this is right

Top-down silica-nanosphere lithography becomes a viable route to III-nitride PEC photodetectors, avoiding the cost and uniformity limits of bottom-up nanowire growth.
A zero-bias UV detector peaked at 365 nm with response extending into the visible could serve in flame sensing, UV monitoring, and optical communication without a power supply.
The sensitivity of responsivity and detectivity to applied bias gives a simple electrical tuning knob for the detector's operating point.
Stable, repeatable on/off switching from 0.7 to 43.5 mW/cm² supports deployment under fluctuating light levels.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

An extension the authors do not make is that the same top-down MQW platform could shift the detection peak by changing quantum-well composition, for example toward AlGaN for solar-blind UV detection or In-richer InGaN for visible response.
Because the photocurrent depends on the solid-liquid interface, tuning nanowire diameter, pitch, and surface passivation beyond the reported 330 nm/900 nm geometry could further raise responsivity, and the paper's own simulation approach is well suited to screening those geometries before fabrication.
The device's response to redox-active species in the electrolyte suggests it could double as a chemical or biological sensor, a mode not tested in this paper.

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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Desk Editor's Note

read the letter

Here's the one-sentence version: the abstract's record responsivity number doesn't square with the maximum photocurrent density and the reported power-law fit. Let me be concrete. If R = J/P, then 16 mA/cm² at 43.5 mW/cm² gives 0.37 A/W at high intensity, while they report 0.33 A/W at 0.7 mW/cm². That already contradicts the claim that responsivity drops with increasing intensity. Throw in the power-law fit with θ = 0.74, and it gets worse: extrapolating from 0.33 A/W at 0.7 mW/cm² gives roughly 4.9 mA/cm² at 43.5 mW/cm², not 16. Conversely, starting from 16 mA/cm² gives R ≈ 1.08 A/W at 0.7 mW/cm². The full text also says maximum responsivity 0.33 A/W at both 5 mW/cm² and 0.7 mW/cm², which is strange if it's supposed to decrease with intensity. So the central 'record' claim cannot be evaluated as written.

What is genuinely new here is the fabrication route: silica nanosphere lithography with top-down etching to make InGaN/GaN MQW nanowire PEC photodetectors. That combination is absent from the cited prior work, which is mostly bottom-up nanowires or planar MQW structures. The fabrication section gives enough detail (sphere diameter, etching chemistry, passivation) to reproduce. The self-powered operation, response time around 168/69 ms, and the stability data look like real measurements, and the NW versus planar comparison shows a doubling in photocurrent density. Credit where it's due.

The soft spots, beyond the numerical inconsistency: Eq. (1) has a unit error—they call I_Light and I_Dark photocurrent densities, then multiply by A, which is dimensionally wrong. If they are currents, the text and numbers need to be clear. There are no error bars, no device statistics, no stated active area, and the planar reference gets only one number. The simulation is presented as qualitative, which is fine, but comparing an experimental responsivity to a simulated trend without a scale is weak. The 'record' claim would need a benchmarking table with matching wavelengths, intensities, and measurement conditions.

My take: the underlying experiment is plausible, and the main flaw is in reporting and analysis, not fabrication or concept. The numbers can be fixed—the authors surely have the raw data. But as written, the abstract and conclusions are not trustworthy because they don't add up. I'd send this to peer review rather than desk reject, because the fabrication route is new and the measurements look real; but I'd expect heavy revision, starting with reconciling the numbers and defining the area convention. A conditional accept at best, only after the data are presented consistently. Recommend a serious referee.

Referee Report

5 major / 5 minor

Summary. The manuscript reports self-powered photoelectrochemical photodetectors (PEC-PDs) based on InGaN/GaN multiple quantum well nanowire arrays fabricated by a scalable top-down silica nanosphere lithography process. The authors claim a record III-nitride PEC-PD responsivity of 330 mA/W at 0.7 mW/cm² under 365 nm illumination, a maximum photocurrent density of 16 mA/cm² at 43.5 mW/cm², a UV-visible rejection ratio of 388, fast response/recovery times, and support from FDTD and drift-diffusion simulations. The central claims are the record responsivity and the scalability of the fabrication route.

Significance. If the reported responsivity and the 'highest among III-nitride PEC-PDs' claim are correct, the work would demonstrate a practical top-down fabrication route for high-performance self-powered PEC photodetectors, with potential impact on UV-visible sensing and IoT applications. The paper clearly identifies a materials system and nanostructuring strategy, and the FDTD/drift-diffusion modeling is an independent exercise that does not appear to be fitted to the target result, which is a strength. However, the headline numbers are not internally consistent as reported, and the missing uncertainty quantification and active-area specification prevent a reliable assessment of the record claim.

major comments (5)

[Eq. (1) and text near it] Equation (1) is dimensionally inconsistent as written: the text defines ILight and IDark as 'photocurrent density' (units A/cm²), but the formula R = (ILight - IDark)/(P × A) divides by both an intensity P (W/cm²) and an area A (cm²), yielding units of A/(W·cm²) rather than A/W. If ILight and IDark are currents, the text should say so; if they are densities, the denominator should be P only. This ambiguity affects every responsivity and detectivity value in the paper, including the headline 0.33 A/W, so it must be resolved and the values recomputed consistently.
[Figure 3(a), Figure 3(b), and Results text] The reported data are internally inconsistent. The Results state a maximum photocurrent density of 16 mA/cm² at 43.5 mW/cm², while Figure 3(b) reports R = 0.33 A/W at 0.7 mW/cm². If R = J/P, then J(0.7) = 0.231 mA/cm²; using the stated power-law fit J ∝ P^0.74 extrapolates to J(43.5) ≈ 4.9 mA/cm², not 16 mA/cm². Conversely, starting from J(43.5) = 16 mA/cm² and the same power law gives J(0.7) ≈ 0.76 mA/cm² and R(0.7) ≈ 1.08 A/W. Even without the fit, the direct ratio 16/43.5 = 0.37 A/W at high intensity exceeds the claimed 0.33 A/W at low intensity, contradicting the statement that responsivity decreases with increasing intensity. This inconsistency must be resolved before the central 'record' claim can be evaluated.
[Figure 2(d) and Figure 3(b) discussions] The text reports the same responsivity value, 0.33 A/W, at two different illumination intensities: once 'under the irradiation of 365 nm wavelength with 5 mW/cm2 power intensity' (in the Figure 2(d) discussion) and once 'under the irradiation light intensity of 0.7 mW/cm2' (in the Figure 3(b) discussion). If the 5 mW/cm² value refers to a spectral measurement at a different operating point, this needs to be stated explicitly; as written, it is an unexplained numerical coincidence that further obscures the intensity dependence.
[Experimental Section / Results] No error bars, device-to-device statistics, or number of measured devices are reported for the photocurrent density, responsivity, or detectivity. The active device area A is never specified, and it is unclear whether A is the geometric footprint of the working electrode, the projected nanowire area, or the total nanowire sidewall area. This is essential for interpreting Eq. (1) and for comparing the 'highest as reported' claim against the literature.
[Figure 2(d) and Theoretical Analysis in SI] The comparison between simulated and experimental spectral responsivity is only qualitative ('similar trend'). No quantitative metrics (e.g., root-mean-square error, correlation coefficient, or a calibration procedure) are provided, and the simulation uses material parameters from literature without a sensitivity analysis. While the simulation is not the central claim, a more rigorous validation is needed to support the statement that the FDTD/drift-diffusion model reproduces the experimental behavior.

minor comments (5)

[Introduction] In the Introduction, the text says 'a high responsivity of 330 mA/cm2' and later '330 mA/cm2' in the abstract context; the unit should be mA/W (or A/W), not mA/cm².
[Figure 1 caption] The caption reads '(b) UV-visible absorption spectra...' but the subfigure labels in the text and the figure should be consistent; the schematic appears to be panel (a), and the SEM/optical spectra panels need clear matching labels.
[Experimental Section] There are several typographical errors, including 'three three-electrode set up' and 'elcterochemical cell'; these should be corrected.
[References] Reference [10] is a duplicate of Reference [5]; the citation numbering should be adjusted.
[Figure 3(b) caption] The caption says 'Light intensity of 43.5 mW/cm2' for panel (c), but the text describes panel (c) as bias-dependent measurements at 43.5 mW/cm²; it would be clearer to say 'at a fixed light intensity of 43.5 mW/cm²' to avoid confusion with the intensity-dependent panel (b).

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the reported responsivity is a direct measurement and the FDTD/drift-diffusion simulation uses independent literature parameters, so no prediction reduces to its own inputs.

full rationale

The paper's central figures of merit—photoresponsivity, detectivity, and EQE—are obtained directly from measured photocurrent and calibrated illumination data rather than from any fitted model. Equation (1) contains a dimensional inconsistency (photocurrent density divided by P×A), but that is a units/correctness issue, not a circularity: the reported responsivity is not defined in terms of a quantity that already assumes the result. The power-law fit (I ∝ P^0.74) is descriptive and is not used to generate the headline responsivity value. The FDTD and drift-diffusion simulations are presented as an independent modeling exercise: the absorption profile is computed from Maxwell's equations and carrier transport from Poisson and continuity equations, with material parameters taken from external cited literature (Table S1). There is no indication that any simulation parameter was adjusted to force agreement with the measured 0.33 A/W or 16 mA/cm² values; the text only claims a similar trend in spectral response. Self-citations (e.g., prior Sadaf nanowire LED/solar work, and a GaN hole mobility reference in the SI) are not load-bearing for the paper's novel claim of a scalable top-down InGaN/GaN MQW PEC photodetector. The 'highest reported' claim is a comparison against external literature, not a conclusion derived from a self-citation chain. The apparent numerical inconsistency between 16 mA/cm² at 43.5 mW/cm² and 0.33 A/W at 0.7 mW/cm² is a data-consistency concern that belongs to correctness review, not circularity analysis. Overall, the derivation chain is self-contained and no circular step is exhibited.

Assumptions & free parameters 1 free parameters · 4 assumptions · 0 invented entities

The central claim (330 mA/W responsivity) does not rely on any fitted free parameter; the only fitted value is the power-law exponent, which is a description of the intensity dependence. The simulation is built on standard physics and literature material parameters. No new physical entities are introduced.

free parameters (1)

power-law exponent theta = 0.74
Fitted to the photocurrent versus light intensity data in Figure 3a to characterize the intensity dependence. It is descriptive and does not determine the central responsivity claim.

assumptions (4)

standard math Maxwell's equations in three dimensions
Used in the FDTD simulation of optical absorption in the nanowire arrays (SI, Theoretical Analysis).
standard math Poisson and drift-diffusion equations
Used to model carrier transport and recombination (Eqs. 3-5 in the main text and SI).
domain assumption InGaN/GaN material parameters from cited literature
Table S1 lists values for mobility, recombination coefficients, effective masses, and work functions. The simulation results depend on these values, and some (e.g., InGaN with 25% In) are not precisely established.
domain assumption PEC water redox mechanism: 2H2O + 4h+ -> O2 + 4H+ and 2H+ + 2e- -> H2
The self-powered photocurrent is attributed to these reactions at the semiconductor-electrolyte interface, but no direct measurement of evolved gases is provided.

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Cite this review

Pith. "Pith review of High-Performance Self-Powered Photoelectrochemical Detection Using Scalable InGaN/GaN Nanowire Arrays." pith.science (2026). https://pith.science/paper/CUYJB2EN

@misc{pith2026250706501,
  author       = {Pith},
  title        = {Pith review of: High-Performance Self-Powered Photoelectrochemical Detection Using Scalable InGaN/GaN Nanowire Arrays},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/CUYJB2EN}},
  note         = {Machine review of arXiv:2507.06501}
}

read the original abstract

Photoelectrochemical photodetectors (PEC-PDs) are promising owing to their simple, low-cost fabrication, self-powered operation, high photoresponse, and environmental sensitivity. In this work, we report for the first time the self-powered PEC photodetection characteristics of nanowire (NW) based green-emitting InGaN/GaN multiple quantum well (MQW) PEC-PDs, fabricated via a scalable top-down approach.The device exhibits strong UV sensitivity with a peak at 365 nm and an extended response into the visible region.Notably, a high photoresponsivity of 330 mA/W was achieved at a lower illumination intensity of 0.7 mW/cm2. Furthermore, the photodetector demonstrates fast, stable, and reproducible performance across varying biases and illumination conditions. These results suggest that InGaN/GaN MQW nanowire-based PEC photodetectors hold strong promise for scalable, efficient, and stable self-powered optoelectronic applications

Discussion (0). Continue with ORCID to comment.

Reference graph

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Pith tools

Reviewed August 6, 2026 · model on record in the stance chip above.

[1] [1]

R., & Tang, C

Park, Y ., Choong, V ., Gao, Y ., Hsieh, B. R., & Tang, C. W. (1996). Work function of indium tin oxide transparent conductor measured by photoelectron spectroscopy. Applied Physics Letters, 68(19), 2699–2701. doi:10.1063/1.116313

work page doi:10.1063/1.116313 1996

[2] [2]

Erin C. H. Kyle, Stephen W. Kaun, Peter G. Burke, Feng Wu, Yuh -Renn Wu, James S. Speck; High-electron-mobility GaN grown on free-standing GaN templates by ammonia- based molecular beam epitaxy. J. Appl. Phys., 115 (19): 193702 (2014)

work page 2014

[3] [3]

M., & Tang, H

Sadaf, S. M., & Tang, H. Mapping the growth of p -type GaN layer under Ga -rich and N- rich conditions at low to high temperatures by plasma-assisted molecular beam epitaxy. Ap- plied Physics Letters, 2020, 117(25), 254104

work page 2020

[4] [4]

Podlipskas, Ž., Jurkevičius, J., Kadys, A. et al. The detrimental effect of AlGaN barrier quality on carrier dynamics in AlGaN/GaN interface. Sci Rep 9, 17346 (2019)

work page 2019

[5] [5]

Development of wide-band gap indium gallium nitride solar cells for high- efficiency photovoltaics

Jani, Omkar K. Development of wide-band gap indium gallium nitride solar cells for high- efficiency photovoltaics. Georgia Institute of Technology, 2008

work page 2008

[6] [6]

Electron mobilities in gallium, indium, and aluminum nitrides

Chin, V . W. L., T. L. Tansley, and T. Osotchan. "Electron mobilities in gallium, indium, and aluminum nitrides." Journal of Applied Physics 75.11 (1994): 7365-7372

work page 1994

[7] [7]

Adjusted surface work function of InN films annealed at vacuum and at high-pressure N2 conditions

Liu, W. F., et al. "Adjusted surface work function of InN films annealed at vacuum and at high-pressure N2 conditions." Materials Letters 95 (2013): 135-138

work page 2013

[8] [8]

E., Li, S

Hsu, L., Jones, R. E., Li, S. X., Yu, K. M., & Walukiewicz, W. (2007). Electron mobility in InN and III-N alloys. Journal of Applied Physics, 102(7), 073705. doi:10.1063/1.2785005

work page doi:10.1063/1.2785005 2007