Updated on 2022/11/01

写真a

 
UESUGI Tsutomu
 
Organization
Institute of Materials and Systems for Sustainability Designated professor
Title
Designated professor

Degree 1

  1. The degree of Doctor of Philosophy ( 2011.3   Hokkaido University ) 

 

Papers 20

  1. Identification of type of threading dislocation causing reverse leakage in GaN p-n junctions after continuous forward current stress Reviewed

    Narita Tetsuo, Kanechika Masakazu, Kojima Jun, Watanabe Hiroki, Kondo Takeshi, Uesugi Tsutomu, Yamaguchi Satoshi, Kimoto Yasuji, Tomita Kazuyoshi, Nagasato Yoshitaka, Ikeda Satoshi, Kosaki Masayoshi, Oka Tohru, Suda Jun

    SCIENTIFIC REPORTS   Vol. 12 ( 1 ) page: 1458   2022.1

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    Authorship:Last author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Scientific Reports  

    Power devices are operated under harsh conditions, such as high currents and voltages, and so degradation of these devices is an important issue. Our group previously found significant increases in reverse leakage current after applying continuous forward current stress to GaN p–n junctions. In the present study, we identified the type of threading dislocations that provide pathways for this reverse leakage current. GaN p–n diodes were grown by metalorganic vapor phase epitaxy on freestanding GaN(0001) substrates with threading dislocation densities of approximately 3 × 105 cm−2. These diodes exhibited a breakdown voltage on the order of 200 V and avalanche capability. The leakage current in some diodes in response to a reverse bias was found to rapidly increase with continuous forward current injection, and leakage sites were identified by optical emission microscopy. Closed-core threading screw dislocations (TSDs) were found at five emission spots based on cross-sectional transmission electron microscopy analyses using two-beam diffraction conditions. The Burgers vectors of these dislocations were identified as [0001] using large-angle convergent-beam electron diffraction. Thus, TSDs for which b = 1c are believed to provide current leakage paths in response to forward current stress.

    DOI: 10.1038/s41598-022-05416-3

    Web of Science

    Scopus

    PubMed

  2. Increase of reverse leakage current at homoepitaxial GaN p-n junctions induced by continuous forward current stress Reviewed

    Narita Tetsuo, Nagasato Yoshitaka, Kanechika Masakazu, Kondo Takeshi, Uesugi Tsutomu, Tomita Kazuyoshi, Ikeda Satoshi, Yamaguchi Satoshi, Kimoto Yasuji, Kosaki Masayoshi, Oka Tohru, Kojima Jun, Suda Jun

    APPLIED PHYSICS LETTERS   Vol. 118 ( 25 ) page: 253501   2021.6

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    Authorship:Last author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Letters  

    Reliability tests involving the application of high electrical stresses were employed to assess GaN-based vertical p-n junctions fabricated on freestanding GaN substrates with threading dislocation densities less than 104 cm−2. Electric field crowding at the device edges was eliminated by employing a shallow bevel mesa structure, thus allowing an evaluation of the reliability of the internal p-n junctions. The p-n diodes exhibited reproducible avalanche breakdown characteristics over the temperature range of 25-175 °C. No degradation was observed even during tests in which the devices were held under a reverse bias near the breakdown voltage. Despite this high degree of reliability in response to reverse bias stress, a small number of diodes were degraded during continuous forward current tests, although the majority of diodes remained unchanged. The reverse leakage current exhibited by degraded diodes was increased with an increase in the forward current density within the range of 50-500 A/cm2, while the breakdown voltages were unchanged in response to current stress. The leakage level increased exponentially with an increase in the total amount of injected carriers but eventually plateaued. In the degraded p-n diode, a luminous point in an emission microscope corresponded to one of the threading dislocations observed in the synchrotron x-ray topography, indicating that a specific dislocation played as a leakage path after injecting carriers.

    DOI: 10.1063/5.0053139

    Web of Science

    Scopus

  3. Mg-implanted bevel edge termination structure for GaN power device applications Reviewed International coauthorship

    Matys Maciej, Ishida Takashi, Nam Kyung Pil, Sakurai Hideki, Narita Tetsuo, Uesugi Tsutomu, Bockowski Michal, Suda Jun, Kachi Tetsu

    APPLIED PHYSICS LETTERS   Vol. 118 ( 9 ) page: 093502   2021.3

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    Authorship:Last author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Letters  

    Herein, we propose and demonstrate the edge termination for GaN-based one-sided abrupt p-n junctions. The structure is comprised of a combination of a shallow negative bevel mesa and selective-area p-type doping under the mesa. Based on the Technology Computer Aided Design (TCAD) simulation, the maximum electric field at the junction edge is markedly reduced to approximately 1.3 times that of the parallel-plane electric field in the proposed structure, which is almost half of the unimplanted diode. The TCAD simulation also shows that the shallow mesa angle of 6 ° effectively reduces the optimum acceptor concentration (Na) in the implanted region and enhances the breakdown voltage. The optimum Na value can be covered by the proposed technology based on the Mg-ion implantation and subsequent ultra-high-pressure annealing (UHPA). Using the formation of the shallow bevel mesa, the Mg-ion implantation, and the UHPA process, we experimentally demonstrate the p-n diodes with a breakdown voltage over 600 V, which is in good agreement with the TCAD simulation. The proposed method can be applied to a vertical trench-gate metal-oxide-semiconductor field-effect transistor with a high figure-of-merit.

    DOI: 10.1063/5.0039183

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  4. Analysis of intrinsic reverse leakage current resulting from band-to-band tunneling in dislocation-free GaN p-n junctions Reviewed

    Shoji Tomoyuki, Narita Tetsuo, Nagasato Yoshitaka, Kanechika Masakazu, Kondo Takeshi, Uesugi Tsutomu, Tomita Kazuyoshi, Ikeda Satoshi, Mori Tomohiko, Yamaguchi Satoshi, Kimoto Yasuji, Kojima Jun, Suda Jun

    APPLIED PHYSICS EXPRESS   Vol. 14 ( 11 ) page: 114001   2021.11

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    Authorship:Last author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Express  

    This work examined reverse leakage currents in GaN p-n junctions nearly free of dislocations. Diodes with shallow bevel mesas and breakdown voltages (BVs) in the range of 130-1000 V exhibited avalanche breakdown at the designed voltages. Significant leakage currents were observed in response to reverse bias values far below the BVs and a weak effect of temperature was also evident. The data were explained based on direct band-to-band tunneling (BTBT). The BTBT current was dominant in those devices having BVs of several hundred volts but was far below the detection limit in the case of a 1000 V class diode.

    DOI: 10.35848/1882-0786/ac2a03

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  5. Design and demonstration of nearly-ideal edge termination for GaN p-n junction using Mg-implanted field limiting rings Reviewed International coauthorship

    Matys Maciej, Ishida Takashi, Nam Kyung Pil, Sakurai Hideki, Kataoka Keita, Narita Tetsuo, Uesugi Tsutomu, Bockowski Michal, Nishimura Tomoaki, Suda Jun, Kachi Tetsu

    APPLIED PHYSICS EXPRESS   Vol. 14 ( 7 ) page: 074002   2021.7

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    Authorship:Last author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Applied Physics Express  

    A nearly-ideal edge termination for GaN p-n junctions was designed and demonstrated using Mg-ions implanted field limiting rings (FLRs). The FLRs were fabricated via the ultra-high-pressure annealing process after implanting Mg-ions into the etched n-type region outside the main p-n junction. The results of the technology computer-aided design simulation indicate that by optimizing the space and width of the rings, the breakdown voltage (BV) can be increased by over 90% of the ideal parallel plane BV (973 V). Accordingly, the fabricated diodes exhibited low leakage current and a BV of 897 V (92% of the ideal BV).

    DOI: 10.35848/1882-0786/ac0b09

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  6. Effect of Nitrogen Plasma Treatment on Characteristics of GaN Trench MOSFETs

    NAM KyungPil, Ishida Takashi, Matys Maciej, Uesugi Tsutomu, Kachi Tetsu, Suda Jun

    JSAP Annual Meetings Extended Abstracts   Vol. 2021.1 ( 0 ) page: 2403 - 2403   2021.2

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    Authorship:Last author   Language:Japanese   Publishing type:Research paper (other academic)   Publisher:The Japan Society of Applied Physics  

    DOI: 10.11470/jsapmeeting.2021.1.0_2403

    CiNii Research

  7. Improvement of channel property of GaN vertical trench MOSFET by compensating nitrogen vacancies with nitrogen plasma treatment

    Ishida Takashi, Nam Kyung Pil, Matys Maciej, Uesugi Tsutomu, Suda Jun, Kachi Tetsu

    APPLIED PHYSICS EXPRESS   Vol. 13 ( 12 )   2020.12

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  8. Improvement of channel property of GaN vertical trench MOSFET by compensating nitrogen vacancies with nitrogen plasma treatment

    Ishida T., Pil Nam K., Matys M., Uesugi T., Suda J., Kachi T.

    Applied Physics Express   Vol. 13 ( 12 )   2020.12

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    Language:Japanese   Publisher:Applied Physics Express  

    The electrical properties of vertical GaN trench MOSFETs without drift layers were evaluated to investigate the effect of nitrogen plasma treatment on the trench sidewalls. It is demonstrated that nitrogen plasma treatment improves the channel property of the vertical GaN trench MOSFET. The possible mechanism of this improvement is the supply of nitrogen atoms from nitrogen plasma treatment to the trench surfaces, and the compensation of the nitrogen vacancies near the trench surfaces by the nitrogen atoms during gate oxide annealing. The temperature dependence and the limiting factors of the channel property are also discussed.

    DOI: 10.35848/1882-0786/abcdbb

    Scopus

  9. Measurement of avalanche multiplication utilizing Franz-Keldysh effect in GaN p-n junction diodes with double-side-depleted shallow bevel termination

    Maeda Takuya, Narita Tetsuo, Ueda Hiroyuki, Kanechika Masakazu, Uesugi Tsutomu, Kachi Tetsu, Kimoto Tsunenobu, Horita Masahiro, Suda Jun

    APPLIED PHYSICS LETTERS   Vol. 115 ( 14 )   2019.9

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    Language:Japanese   Publisher:Applied Physics Letters  

    Avalanche multiplication characteristics of GaN p-n junction diodes (PNDs) with double-side-depleted shallow bevel termination, which exhibit nearly ideal avalanche breakdown, were investigated by photomultiplication measurements using sub-bandgap light. In GaN PNDs under reverse bias conditions, optical absorption induced by the Franz-Keldysh (FK) effect is observed, resulting in a predictable photocurrent. The avalanche multiplication factors were extracted as a ratio of the measured values to the calculated FK-induced photocurrent. In addition, the temperature dependences of the avalanche multiplications were also investigated.

    DOI: 10.1063/1.5114844

    Web of Science

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  10. Shockley-Read-Hall lifetime in homoepitaxial p-GaN extracted from recombination current in GaN p-n(+) junction diodes

    Maeda Takuya, Narita Tetsuo, Ueda Hiroyuki, Kanechika Masakazu, Uesugi Tsutomu, Kachi Tetsu, Kimoto Tsunenobu, Horita Masahiro, Suda Jun

    JAPANESE JOURNAL OF APPLIED PHYSICS   Vol. 58 ( SC )   2019.6

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    Language:Japanese   Publisher:Japanese Journal of Applied Physics  

    The Shockley-Read-Hall (SRH) lifetime in homoepitaxial p-GaN (N a = 1 × 1017 cm-3) is investigated by analyzing forward current-voltage (I-V) characteristics in GaN-on-GaN p-n+ junction diodes with mesa-isolation structure. The ideality factor around 2 due to recombination current was obtained in the 1.8-2.7 V window, which is different from the characteristic of a p+-n- junction involving considerable diffusion current. The recombination current was proportional to the junction area, indicating that the recombination current is a bulk component, not a mesa-surface component. Analyzing the recombination current with consideration of the SRH recombination rate in the depletion layer, we obtained an SRH lifetime of 46 ps at 298 K. The temperature dependence of the I-V characteristics was also investigated and the SRH lifetimes were extracted in the range of 223-573 K. The SRH lifetime in homoepitaxial p-GaN followed the empirical power law of = 1.2 × 10-16 × T 2.25 (s).

    DOI: 10.7567/1347-4065/ab07ad

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  11. Design and Fabrication of GaN p-n Junction Diodes With Negative Beveled-Mesa Termination

    Maeda Takuya, Narita Tetsuo, Ueda Hiroyuki, Kanechika Masakazu, Uesugi Tsutomu, Kachi Tetsu, Kimoto Tsunenobu, Horita Masahiro, Suda Jun

    IEEE ELECTRON DEVICE LETTERS   Vol. 40 ( 6 ) page: 941 - 944   2019.6

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    Language:Japanese   Publisher:IEEE Electron Device Letters  

    We report on homoepitaxial GaN p-n junction diodes with a negative beveled-mesa termination. The electric field distribution in a beveled-mesa was investigated using TCAD simulation, and the devices were designed using currently available GaN growth techniques. Shallow-angle (ca. 10°) negative bevel GaN p-n junction diodes were fabricated with various Mg acceptor concentrations in the p-layers. The suppression of electric field crowding and improvement of the breakdown voltage were observed, as the Mg concentration was decreased. The parallel-plane breakdown field of 2.86 MV/cm was obtained for a device with the breakdown voltage of 425 V.

    DOI: 10.1109/LED.2019.2912395

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  12. Estimation of Impact Ionization Coefficient in GaN by Photomulitiplication Measurement Utilizing Franz-Keldysh Effect

    Maeda T., Narita T., Ueda H., Kanechika M., Uesugi T., Kachi T., Kimoto T., Horita M., Suda J.

    Proceedings of the International Symposium on Power Semiconductor Devices and ICs   Vol. 2019-May   page: 59 - 62   2019.5

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    Language:Japanese   Publisher:Proceedings of the International Symposium on Power Semiconductor Devices and ICs  

    A valanche multiplication characteristics in GaN p-n junction diodes (PNDs) under high reverse bias conditions were investigated. The GaN-on-GaN PNDs with double-side-depleted shallow bevel termination, which showed low reverse leakage current and excellent avalanche capability, were used for the measurements. Under sub-bandgap light illumination, the photocurrents induced by Franz-Keldysh (FK) effect, which can be well reproduced by the theoretical calculations of the optical absorption, and their avalanche multiplications were observed. The multiplication factors were extracted as the ratios of the experimental photocurrents to the calculated FK-induced photocurrent. Under an assumption of equal impact ionization coefficients of electrons and holes, the electric-field dependence of an impact ionization coefficient in GaN were estimated.

    DOI: 10.1109/ISPSD.2019.8757676

    Scopus

  13. Estimation of Impact Ionization Coefficient in GaN by Photomulitiplication Measurement Utilizing Franz-Keldysh Effect

    Maeda Takuya, Narita Tetsuo, Ueda Hiroyuki, Kanechika Masakazu, Uesugi Tsutomu, Kachi Tetsu, Kimoto Tsunenobu, Horita Masahiro, Suda Jun

    2019 31ST INTERNATIONAL SYMPOSIUM ON POWER SEMICONDUCTOR DEVICES AND ICS (ISPSD)     page: 59 - 62   2019

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  14. Franz-Keldysh effect in GaN p-n junction diode under high reverse bias voltage

    Maeda Takuya, Narita Tetsuo, Kanechika Masakazu, Uesugi Tsutomu, Kachi Tetsu, Kimoto Tsunenobu, Horita Masahiro, Suda Jun

    APPLIED PHYSICS LETTERS   Vol. 112 ( 25 )   2018.6

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    Language:Japanese   Publisher:Applied Physics Letters  

    Photocurrent induced by sub-bandgap light absorption due to the Franz-Keldysh effect was observed in GaN p-n junction diodes under a high reverse bias voltage. The photocurrent increased with the reverse bias voltage and the increase was found to be more significant as the wavelength approached the absorption edge of GaN. The photocurrent was calculated with consideration of light absorption induced by the Franz-Keldysh effect in the depletion layer. The calculated curves showed excellent agreement with the experimental curves. The photocurrent also increased with an increase in temperature and this could be quantitatively explained by the red-shift of the GaN absorption edge with the increase in temperature.

    DOI: 10.1063/1.5031215

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  15. Cathodoluminescence Study on Thermal Recovery Process of Mg-Ion Implanted N-Polar GaN

    Kataoka Keita, Narita Tetsuo, Iguchi Hiroko, Uesugi Tsutomu, Kachi Tetsu

    PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS   Vol. 255 ( 5 )   2018.5

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    Language:Japanese   Publisher:Physica Status Solidi (B) Basic Research  

    Thermal recovery of N-polar GaN(000 (0001) samples implanted with magnesium and hydrogen ions was investigated by cathodoluminescence (CL) spectroscopy. The high thermal stability of N-polar GaN allowed annealing process over 1200 °C without protective overlayer. The CL emissions from acceptor-bound excitons and donor-bound excitons were observed in the near-band-edge (NBE) after annealing over 1000 °C of the ion implanted samples, which indicates the formation of Mg acceptors. The emission intensities both in the NBE and in the green luminescence (GL) band increased with the annealing temperature, resulting from reducing the non-radiative recombination centers. On the other hand, the enhancement of the GL band (nitrogen vacancy complexes) by prolonging the annealing duration above 1200 °C was not significant as compared to the band-edge emission, probably resulting from the enhancement of activating the implanted Mg ions. These results give clear directions to improve the quality of Mg-ion implanted GaN.

    DOI: 10.1002/pssb.201700379

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  16. Sources of carrier compensation in metalorganic vapor phase epitaxy-grown homoepitaxial n-type GaN layers with various doping concentrations

    Sawada Naoki, Narita Tetsuo, Kanechika Masakazu, Uesugi Tsutomu, Kachi Tetsu, Horita Masahiro, Kimoto Tsunenobu, Suda Jun

    APPLIED PHYSICS EXPRESS   Vol. 11 ( 4 )   2018.4

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    Language:Japanese   Publisher:Applied Physics Express  

    The source of carrier compensation in metalorganic vapor phase epitaxy (MOVPE)-grown n-type GaN was quantitatively investigated by Halleffect measurement, deep-level transient spectroscopy, and secondary ion mass spectrometry. These analysis techniques revealed that there were at least three different compensation sources. The carrier compensation for samples with donor concentrations below 5 1016 cm3 can be explained by residual carbon and electron trap E3 (EC % 0.6 eV). For samples with higher donor concentrations, we found a proportional relationship between donor concentration and compensating acceptor concentration, which resulted from a third source of compensation. This is possibly due to the self-compensation effect.

    DOI: 10.7567/APEX.11.041001

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  17. Parallel-Plane Breakdown Fields of 2.8-3.5 MV/cm in GaN-on-GaN p-n Junction Diodes with Double-Side-Depleted Shallow Bevel Termination

    Maeda T., Narita T., Ueda H., Kanechika M., Uesugi T., Kachi T., Kimoto T., Horita M., Suda J.

    2018 IEEE INTERNATIONAL ELECTRON DEVICES MEETING (IEDM)     2018

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  18. Ion implantation technique for conductivity control of GaN

    Narita T., Kataoka K., Kanechika M., Kachi T., Uesugi T.

    17th International Workshop on Junction Technology, IWJT 2017     page: 87 - 90   2017.6

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    Language:Japanese   Publisher:17th International Workshop on Junction Technology, IWJT 2017  

    Ion implantation technique for controlling n- or p-type conduction has been a significant challenge for GaN-based high-power devices to achieve levels approaching their theoretical limits of performance. Previous studies on n-type conduction of GaN through Si ion implantation achieved 86% [1] and approximately 100% [2] of activation rate after annealing at 1250 and 1400 °C, respectively. Such high-temperature annealing results in serious surface degradation of GaN(0001) due to decomposition [1], thereby needing a protective layer. However, it is difficult to make a proper choice of a protective layer which remains unaltered and is removable after annealing above 1200°C. Therefore achieving the high-activation rate at lower temperature is a very important practice. On the other hand, the Mg-ion implantation for p-type conductivity is more challenging due to the higher-temperature annealing required for electrical activation, resulting in a major difficulty protecting the surface. The formation energy of Mg on the Ga site (MgGa) at the position of Fermi level near the valence band is about 1 eV higher than that of SiGa at the Fermi level near the conduction band [4, 5], which may explain the difference of required annealing temperature for different conduction types.

    DOI: 10.23919/IWJT.2017.7966524

    Scopus

  19. P-type doping of GaN(000(1)over-bar) by magnesium ion implantation

    Narita Tetsuo, Kachi Tetsu, Kataoka Keita, Uesugi Tsutomu

    APPLIED PHYSICS EXPRESS   Vol. 10 ( 1 )   2017.1

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    Language:Japanese   Publisher:Applied Physics Express  

    Magnesium ion implantation has been performed on a GaN(0001) substrate, whose surface has a high thermal stability, thus allowing postimplantation annealing without the use of a protective layer. The current-voltage characteristics of p-n diodes fabricated on GaN(0001) showed distinct rectification at a turn-on voltage of about 3V, although the leakage current varied widely among the diodes. Coimplantation with magnesium and hydrogen ions effectively suppressed the leakage currents and device-to-device variations. In addition, an electroluminescence band was observed at wavelengths shorter than 450nm for these diodes. These results provide strong evidence that implanted magnesium ions create acceptors in GaN(0001).

    DOI: 10.7567/APEX.10.016501

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  20. Ion implantation technique for conductivity control of GaN

    Narita Tetsuo, Kataoka Keita, Kanechika Masakazu, Kachi Tetsu, Uesugi Tsutomu

    2017 17TH INTERNATIONAL WORKSHOP ON JUNCTION TECHNOLOGY (IWJT)     page: 87 - 90   2017

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