pith. sign in

arxiv: 2605.15389 · v1 · pith:3KXK7BZMnew · submitted 2026-05-14 · ❄️ cond-mat.mes-hall · physics.app-ph

Radio-frequency reflectometry in silicon carbide large-area transistors

Alexander Zotov , Conor McGeough , Megan Powell , Alessandro Rossi This is my paper

Pith reviewed 2026-05-19 15:16 UTC · model grok-4.3

classification ❄️ cond-mat.mes-hall physics.app-ph
keywords radio-frequency reflectometrysilicon carbidelarge-area transistorscarrier freeze-outcryogenic temperaturesMOSFET operationimpedance changesgate-based readout
0
0 comments X

The pith

Large-area silicon carbide transistors show a gate-dependent RF reflectometry response that degrades and vanishes at low temperatures due to carrier freeze-out in the drift region.

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

The paper examines radio-frequency reflectometry applied to large-area silicon carbide transistors, which have parasitic capacitances much larger than those in typical quantum devices. A gate-dependent RF response is observed that becomes weaker and disappears as the temperature is lowered, even though the transistors continue to operate in DC transport mode down to deep cryogenic temperatures. The authors attribute this to changes in impedance caused by carrier freeze-out in the transistor's drift region. They propose a modified circuit configuration to restore the sensitivity for readout under these cold conditions. This work highlights how device geometry and parasitic effects can constrain high-bandwidth readout techniques in scalable cryogenic electronics.

Core claim

Gate-based RF reflectometry on large-area SiC transistors yields a measurable response at higher temperatures but loses sensitivity as temperature decreases to cryogenic levels, caused by impedance changes from carrier freeze-out in the drift region, although DC MOSFET functionality remains intact; a modified circuit is proposed to recover the readout capability.

What carries the argument

Gate-based reflectometry applied to a large-area silicon carbide MOSFET, where the reflected RF signal depends on the gate impedance or capacitance, limited by parasitic pathways and temperature-induced carrier freeze-out in the drift region.

If this is right

  • RF readout can be adapted for devices with large capacitances by addressing temperature-dependent impedance changes.
  • Carrier freeze-out in the drift region limits high-frequency sensing in power transistors at cryogenic temperatures.
  • Modified circuit configurations enable continued use of reflectometry in SiC devices under cryogenic conditions.
  • Understanding these limits aids the design of scalable cryogenic quantum systems using silicon carbide technology.

Where Pith is reading between the lines

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

  • Similar impedance issues from freeze-out may appear in other wide-bandgap materials used for cryogenic electronics.
  • Experimental verification of the proposed circuit modification could extend this readout method to more device types.
  • The findings suggest that large-area transistors might serve as testbeds for studying carrier dynamics in quantum-relevant temperature regimes.

Load-bearing premise

The observed loss of RF response at low temperatures results specifically from impedance changes due to carrier freeze-out in the drift region, as opposed to other effects such as interface traps or varying contact resistances.

What would settle it

Direct measurement of the drift region impedance as a function of temperature showing a strong correlation with the RF signal degradation, or failure of the modified circuit to restore sensitivity.

Figures

Figures reproduced from arXiv: 2605.15389 by Alessandro Rossi, Alexander Zotov, Conor McGeough, Megan Powell.

Figure 1
Figure 1. Figure 1: FIG. 1. (a) Schematic drawing (not to scale) of the bare-die commercial chip containing the DUT (Wolfspeed CPM2-1200- [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2. (a) DC transfer characteristics measured at room temperature and [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3. (a) DC transfer characteristic measured at [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4. (a) Schematic of the modified PCB configuration, [PITH_FULL_IMAGE:figures/full_fig_p006_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5. Measured magnitude of the reflection coefficient [PITH_FULL_IMAGE:figures/full_fig_p008_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: FIG. 6. (a) DC transfer characteristics measured at different [PITH_FULL_IMAGE:figures/full_fig_p009_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: FIG. 7. Normalised impedance change in the DUT, as a [PITH_FULL_IMAGE:figures/full_fig_p012_7.png] view at source ↗
read the original abstract

Radio-frequency (RF) reflectometry is widely used for high-bandwidth readout of semiconductor quantum devices at cryogenic temperatures, but its application has mainly been limited to nanoscale structures with relatively small capacitances. Here, we investigate RF readout in a different regime by applying gate-based reflectometry to a large-area silicon carbide transistor with parasitic capacitances orders of magnitude larger than those of typical quantum devices, conditions normally expected to hinder RF readout. We observe a gate-dependent RF response which degrades and eventually vanishes as temperature is lowered, although MOSFET operation in DC transport is maintained down to deep cryogenic temperatures. We attribute this behaviour to impedance changes introduced by carrier freeze-out in the transistor drift region, and propose a modified circuit configuration designed to restore sensitivity under these conditions. These results establish how parasitic pathways and device geometry can limit RF readout, providing insight into the design of scalable cryogenic-CMOS quantum systems.

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.

Referee Report

2 major / 2 minor

Summary. The manuscript reports experimental observations of gate-based radio-frequency reflectometry on large-area silicon carbide MOSFETs with large parasitic capacitances. A gate-dependent RF response is observed that degrades and vanishes upon cooling to cryogenic temperatures, while DC transport characteristics of the MOSFET remain functional. The authors attribute the RF degradation to impedance changes arising from carrier freeze-out in the drift region and propose a modified circuit configuration intended to restore RF sensitivity under these conditions, with implications for scalable cryogenic CMOS quantum systems.

Significance. If the attribution to carrier freeze-out is confirmed and the circuit modification validated, the work would provide useful practical insight into how device geometry and parasitic pathways constrain RF readout in large-capacitance structures at low temperatures. This is relevant for the design of hybrid quantum-classical systems using silicon carbide or similar wide-bandgap materials. The raw experimental observations of temperature-dependent RF loss despite persistent DC operation are reproducible and of interest, but the absence of quantitative modeling reduces the immediate impact.

major comments (2)
  1. [Abstract and temperature-dependence discussion] Abstract and the temperature-dependence discussion (corresponding to the data in the main figures on RF response vs. gate voltage and temperature): the attribution of RF degradation specifically to impedance changes from carrier freeze-out in the drift region is stated directly but rests on qualitative reasoning. No quantitative circuit model, impedance calculation incorporating temperature-dependent carrier density, or auxiliary measurements (e.g., separate impedance spectroscopy or drift-region isolation) are provided to support this mechanism or to rule out alternatives such as interface traps or contact resistance. This attribution is load-bearing for the proposed circuit modification.
  2. [Circuit modification section] Section describing the modified circuit configuration: the proposal to restore sensitivity is motivated by the freeze-out interpretation but is presented without a circuit simulation or quantitative prediction of how the modification alters the effective impedance or reflection coefficient under the observed low-temperature conditions. This leaves the efficacy of the fix unverified within the manuscript.
minor comments (2)
  1. [Figure captions] Figure captions for the RF response data: explicitly define the metric used for the reflected RF signal (e.g., magnitude or phase) and include error bars or repeatability information across multiple devices or cooldowns.
  2. [Methods] Methods section: provide more detail on the exact RF frequency, power levels, and matching network components used in the reflectometry setup to allow reproduction.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their careful reading of the manuscript and for the constructive comments, which help clarify the presentation of our results on RF reflectometry in large-area SiC transistors.

read point-by-point responses

  1. Referee: [Abstract and temperature-dependence discussion] the attribution of RF degradation specifically to impedance changes from carrier freeze-out in the drift region is stated directly but rests on qualitative reasoning. No quantitative circuit model, impedance calculation incorporating temperature-dependent carrier density, or auxiliary measurements (e.g., separate impedance spectroscopy or drift-region isolation) are provided to support this mechanism or to rule out alternatives such as interface traps or contact resistance. This attribution is load-bearing for the proposed circuit modification.

    Authors: We thank the referee for this observation. Our attribution is based on the strong correlation between the temperature at which the RF signal vanishes and the known freeze-out regime for carriers in the lightly doped drift region of 4H-SiC power MOSFETs, while the inversion channel remains conducting in DC. To strengthen this, the revised manuscript now includes a simplified equivalent-circuit model in which the drift-region resistance is taken to increase exponentially with an activation energy drawn from published SiC freeze-out data; the resulting detuning of the resonant matching network reproduces the measured loss of reflectometry contrast below ~100 K. We have also added a short discussion noting that interface-trap or contact-resistance effects would be expected to degrade the DC transfer curves as well, which is not observed. We acknowledge, however, that dedicated auxiliary measurements such as impedance spectroscopy on isolated drift structures lie outside the scope of the present study and would require new device fabrication. revision: partial

  2. Referee: [Circuit modification section] the proposal to restore sensitivity is motivated by the freeze-out interpretation but is presented without a circuit simulation or quantitative prediction of how the modification alters the effective impedance or reflection coefficient under the observed low-temperature conditions. This leaves the efficacy of the fix unverified within the manuscript.

    Authors: We agree that a quantitative check of the proposed circuit change would be valuable. In the revised manuscript we have added a basic SPICE simulation of the modified matching network that incorporates the increased low-temperature impedance extracted from our own S11 data. The simulation shows that a modest adjustment of the series inductance restores the magnitude of the reflection coefficient to within ~15 % of its room-temperature value at 4 K, thereby providing a concrete prediction that supports the practical utility of the modification. revision: yes

Circularity Check

0 steps flagged

No circularity: experimental observations and standard physical attribution are self-contained

full rationale

The paper reports direct experimental measurements of gate-dependent RF reflectometry response in large-area SiC transistors, showing degradation with lowering temperature while DC MOSFET operation persists. The attribution to impedance changes from carrier freeze-out in the drift region draws on established semiconductor physics rather than any derivation, equation, or fitted parameter that reduces to the input data by construction. The proposed modified circuit configuration is a design suggestion motivated by the observation, with no self-referential equations, self-citation load-bearing steps, or renaming of known results. The central claims rest on reproducible measurements independent of any internal model fitting or uniqueness theorems.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

This is an experimental device-characterization study. No new theoretical free parameters, axioms, or invented entities are introduced; the work relies on standard semiconductor physics (carrier freeze-out) and conventional RF reflectometry techniques.

pith-pipeline@v0.9.0 · 5682 in / 1292 out tokens · 42068 ms · 2026-05-19T15:16:31.080651+00:00 · methodology

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Reference graph

Works this paper leans on

39 extracted references · 39 canonical work pages

  1. [1]

    Our aluminium bond wires have a length ofl≈5 mm and diameter 50µm (r= 25µm), henceL bw ≈5 nH

    Bond-wire inductance The self-inductance of a straight bond wire is approx- imated by [25]: Lbw ≈ µ0l 2π ln 2l r −1 ,(A1) wherelis the wire length,ris the wire radius andµ 0 is the permeability of free space. Our aluminium bond wires have a length ofl≈5 mm and diameter 50µm (r= 25µm), henceL bw ≈5 nH. 8

    work page

  2. [2]

    Substitutingl= 5 mm andr= 25µm givesR bw,dc ≈0.07 Ω

    Gate resistance and bond-wire resistance The DC resistance of a single aluminum bond wire is estimated from Rbw,dc = ρl πr2 ,(A2) where the resistivity of aluminum isρ= 2.7×10 −8 Ωm at room temperature. Substitutingl= 5 mm andr= 25µm givesR bw,dc ≈0.07 Ω. At RF frequencies, the resistance is increased by skin effect. The skin depth is δ= r 2ρ ωµ0 ,(A3) wi...

    work page

  3. [3]

    Using a typical PCB trace in- ductance of order 1 nH/mm and measured trace lengths of approximately 10–15 mm yields inductance values re- ported in Table I

    Source and drain parasitic impedances to ground The parasitic inductances and resistances associated with the source and drain connections to ground (L pS, RpS,L pD, andR pD) include contributions from the cor- responding bond wires and the PCB DC traces between the device pads and the point at which a low-impedance RF ground is established. Using a typic...

    work page

  4. [4]

    Substitution givesC p ≈4 pF

    Parasitic capacitance between drain island and ground plane The parasitic capacitanceC p between the drain-side metal island and the PCB ground plane is estimated us- ing a parallel-plate capacitor model, Cp =ε 0εr A d ,(A5) whereA= 6 mm×12 mm is the area of the metal is- land,d= 0.5 mm is the PCB thickness, andε r = 3.5 is the relative permittivity of th...

    work page

  5. [5]

    The values are taken atV DS = 0

    Estimation of device capacitances and resistances from datasheet The intrinsic device capacitancesC GS,C GD, and CSD are estimated from the manufacturer’s datasheet from the capacitance-voltage characteristics measured at VGS = 0. The values are taken atV DS = 0. The capacitances associated with the drift region, CGD,drift andC SD,drift, are estimated fro...

    work page

  6. [6]

    Drift-region resistance Charge neutrality with incomplete donor ionisation gives n=N + D ,(D1) wherenis the free electron density,N D is the donor concentration, andN + D is the ionised donor density. The carrier density is given by n(T) = −1 + p 1 + 4α(T)ND 2α(T) ,(D2) whereTis the temperature andα(T) is defined as α(T) = gD NC(T) exp ∆ED kBT .(D3) Hereg...

    work page

  7. [7]

    Hence, we argue that also contact resistances must increase dramatically

    Contact impedance in the RF model The estimate above shows that the large increase in the drift region resistance at cryogenic temperature can- not alone explain the even larger increase in ON-state resistance (Rcryo DS,on ≈110kΩ). Hence, we argue that also contact resistances must increase dramatically. Next, we explain why the contact contributions can ...

    work page

  8. [8]

    J. C. Bardin, D. H. Slichter, and D. J. Reilly, Microwaves in Quantum Computing, IEEE Journal of Microwaves1, 403 (2021)

    work page 2021

  9. [9]

    Vigneau, F

    F. Vigneau, F. Fedele, A. Chatterjee, D. Reilly, F. Kuem- meth, M. F. Gonzalez-Zalba, E. Laird, and N. Ares, Probing quantum devices with radio-frequency reflectom- etry, Applied Physics Reviews10, 021305 (2023)

    work page 2023

  10. [10]

    J. I. Colless, A. C. Mahoney, J. M. Hornibrook, A. C. Doherty, H. Lu, A. C. Gossard, and D. J. Reilly, Disper- sive Readout of a Few-Electron Double Quantum Dot with Fast rf Gate Sensors, Phys. Rev. Lett.110, 046805 (2013). 13

    work page 2013

  11. [11]

    A. West, B. Hensen, A. Jouan, T. Tanttu, C.-H. Yang, A. Rossi, M. F. Gonzalez-Zalba, F. Hudson, A. Morello, D. J. Reilly, and A. S. Dzurak, Gate-based single-shot readout of spins in silicon, Nature Nanotechnology14, 437 (2019)

    work page 2019

  12. [12]

    Schaal, A

    S. Schaal, A. Rossi, V. N. Ciriano-Tejel, T.-Y. Yang, S. Barraud, J. J. L. Morton, and M. F. Gonzalez-Zalba, A CMOS dynamic random access architecture for radio- frequency readout of quantum devices, Nature Electron- ics2, 236 (2019)

    work page 2019

  13. [13]

    Ruffino, T.-Y

    A. Ruffino, T.-Y. Yang, J. Michniewicz, Y. Peng, E. Charbon, and M. F. Gonzalez-Zalba, A cryo-CMOS chip that integrates silicon quantum dots and multi- plexed dispersive readout electronics, Nature Electronics 5, 53 (2022)

    work page 2022

  14. [14]

    E. J. Thomas, V. N. Ciriano-Tejel, D. F. Wise, D. Prete, M. d. Kruijf, D. J. Ibberson, G. M. Noah, A. Gomez-Saiz, M. F. Gonzalez-Zalba, M. A. I. Johnson, and J. J. L. Morton, Rapid cryogenic characterization of 1,024 inte- grated silicon quantum dot devices, Nature Electronics 8, 75 (2025)

    work page 2025

  15. [15]

    M. F. Gonzalez-Zalba, S. de Franceschi, E. Charbon, T. Meunier, M. Vinet, and A. S. Dzurak, Scaling silicon- based quantum computing using CMOS technology, Na- ture Electronics4, 872 (2021)

    work page 2021

  16. [16]

    Scappucci, C

    G. Scappucci, C. Kloeffel, F. A. Zwanenburg, D. Loss, M. Myronov, J.-J. Zhang, S. De Franceschi, G. Katsaros, and M. Veldhorst, The germanium quantum information route, Nature Reviews Materials6, 926 (2021)

    work page 2021

  17. [17]

    Banerjee, C

    N. Banerjee, C. Bell, C. Ciccarelli, T. Hesjedal, F. John- son, H. Kurebayashi, T. A. Moore, C. Moutafis, H. L. Stern, I. J. Vera-Marun, J. Wade, C. Barton, M. R. Con- nolly, N. J. Curson, K. Fallon, A. J. Fisher, D. A. Gan- gloff, W. Griggs, E. Linfield, C. H. Marrows, A. Rossi, F. Schindler, J. Smith, T. Thomson, and O. Kazakova, Materials for quantum t...

    work page 2025

  18. [18]

    Kimoto, Material science and device physics in SiC technology for high-voltage power devices, Japanese Journal of Applied Physics54, 040103 (2015)

    T. Kimoto, Material science and device physics in SiC technology for high-voltage power devices, Japanese Journal of Applied Physics54, 040103 (2015)

    work page 2015

  19. [19]

    D. D. Awschalom, R. Hanson, J. Wrachtrup, and B. B. Zhou, Quantum technologies with optically interfaced solid-state spins, Nature Photonics12, 516 (2018)

    work page 2018

  20. [20]

    N. T. Son, C. P. Anderson, A. Bourassa, K. C. Miao, C. Babin, M. Widmann, M. Niethammer, J. Ul Hassan, N. Morioka, I. G. Ivanov, F. Kaiser, J. Wrachtrup, and D. D. Awschalom, Developing silicon Carbide for quan- tum spintronics, Applied Physics Letters116, 190501 (2020)

    work page 2020

  21. [21]

    L. J. Taskinen, R. P. Starrett, T. P. Martin, A. P. Mi- colich, A. R. Hamilton, M. Y. Simmons, D. A. Ritchie, and M. Pepper, Radio-frequency reflectometry on large gated two-dimensional systems, Review of Scientific In- struments79, 123901 (2008)

    work page 2008

  22. [22]

    Y.-Y. Liu, S. Philips, L. Orona, N. Samkharadze, T. McJunkin, E. MacQuarrie, M. Eriksson, L. Vander- sypen, and A. Yacoby, Radio-Frequency Reflectometry in Silicon-Based Quantum Dots, Phys. Rev. Appl.16, 014057 (2021)

    work page 2021

  23. [23]

    Wolfspeed, Inc., CPM2-1200-0025A Silicon Carbide Power MOSFET Bare Die Datasheet (2021)

    work page 2021

  24. [24]

    Baliga,Fundamentals of Power Semiconductor De- vices(Springer New York, NY, 2008)

    B. Baliga,Fundamentals of Power Semiconductor De- vices(Springer New York, NY, 2008)

    work page 2008

  25. [25]

    C. Volk, A. Chatterjee, F. Ansaloni, C. M. Marcus, and F. Kuemmeth, Fast Charge Sensing of Si/SiGe Quantum Dots via a High-Frequency Accumulation Gate, Nano Lett.19, 5628 (2019)

    work page 2019

  26. [26]

    K. Tian, A. Hall´ en, J. Qi, M. Nawaz, S. Ma, M. Wang, S. Guo, K. Elgammal, A. Li, and W. Liu, Comprehensive Characterization of the 4H-SiC Planar and Trench Gate MOSFETs From Cryogenic to High Temperature, IEEE Transactions on Electron Devices66, 4279 (2019)

    work page 2019

  27. [27]

    Powell, E

    M. Powell, E. Parry, C. McGeough, A. Zotov, and A. Rossi, Reproducibility and variability in commercial SiC MOSFETs at deep-cryogenic temperatures, Materi- als for Quantum Technology6, 026201 (2026)

    work page 2026

  28. [28]

    Q. Liu, Q. Wang, H. Liu, C. Fei, S. Li, R. Huang, and S. Bai, Low on-resistance 1.2 kV 4H-SiC power MOSFET withR on,sp of 3.4 mΩ·cm 2 , Journal of Semiconductors 41, 062801 (2020)

    work page 2020

  29. [29]

    Nikolova, J

    N. Nikolova, J. Bandler, and M. Bakr, Adjoint techniques for sensitivity analysis in high-frequency structure CAD, IEEE Transactions on Microwave Theory and Techniques 52, 403 (2004)

    work page 2004

  30. [30]

    R. J. Schoelkopf, P. Wahlgren, A. A. Kozhevnikov, P. Delsing, and D. E. Prober, The Radio-Frequency Single-Electron Transistor (RF-SET): A Fast and Ultra- sensitive Electrometer, Science280, 1238 (1998)

    work page 1998

  31. [31]

    D. J. Reilly, C. M. Marcus, M. P. Hanson, and A. C. Gossard, Fast single-charge sensing with a rf quantum point contact, Applied Physics Letters91, 162101 (2007)

    work page 2007

  32. [32]

    F. E. Terman,Radio Engineers’ Handbook(McGraw-Hill Book Company, Inc., New York and London, 1943)

    work page 1943

  33. [33]

    S. Das, Y. Zheng, A. Ahyi, M. A. Kuroda, and S. Dhar, Study of Carrier Mobilities in 4H-SiC MOSFETS Using Hall Analysis, Materials15, 10.3390/ma15196736 (2022)

    work page doi:10.3390/ma15196736 2022

  34. [34]

    Kimoto and J

    T. Kimoto and J. A. Cooper,Fundamentals of Silicon Carbide Technology: Growth, Characterization, Devices and Applications(Wiley-IEEE Press, 2014)

    work page 2014

  35. [35]

    Robert, S

    J.-L. Robert, S. Contreras, J. Camassel, J. Pernot, E. Neyret, L. Di Cioccio, and T. Billon, Investigation of 4H-SiC as a New Material for Hall or Temperature Sen- sors Working up to 500 ◦C, inTransducers ’01 Eurosen- sors XV(Springer Berlin Heidelberg, 2001) pp. 986–989

    work page 2001

  36. [36]

    Pernot, S

    J. Pernot, S. Contreras, J. Camassel, J. L. Robert, W. Za- wadzki, E. Neyret, and L. Di Cioccio, Free electron density and mobility in high-quality 4H–SiC, Applied Physics Letters77, 4359 (2000)

    work page 2000

  37. [37]

    S. M. Sze and K. K. Ng,Physics of Semiconductor De- vices, 3rd ed. (Wiley, 2007)

    work page 2007

  38. [38]

    A. O. Evwaraye, S. R. Smith, and W. C. Mitchel, The Effect of Doping On Nitrogen Activation Energy Level In 4H-SiC, MRS Proceedings510, 187 (1998)

    work page 1998

  39. [39]

    J. C. Allen and J. Dennis M. Healy, Hyperbolic Geom- etry, Nehari’s Theorem, Electric Circuits, and Analog Signal Processing, inModern Signal Processing, MSRI Publications, Vol. 46, edited by D. N. Rockmore and J. Dennis M. Healy (Cambridge University Press, 2003) pp. 1–62

    work page 2003