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18.  Type-II InAs/GaSb Superlattices and Detectors with Cutoff Wavelength Greater Than 18 μm
M. Razeghi, Y. Wei, A. Gin, G.J. Brown and D. Johnstone
Proceedings of the SPIE, San Jose, CA, Vol. 4650, 111 (2002)-- January 25, 2002 ...[Visit Journal]
The authors report the most recent advances in Type-II InAs/GaSb superlattice materials and photovoltaic detectors. Lattice mismatch between the substrate and the superlattice has been routinely achieved below 0.1%, and less than 0.0043% as the record. The FWHM of the zeroth order peak from x-ray diffraction has been decreased below 50 arcsec and a record of less than 44arcsec has been achieved. High performance detectors with 50% cutoff beyond 18 micrometers up to 26 micrometers have been successfully demonstrated. The detectors with a 50% cut-off wavelength of 18.8 micrometers showed a peak current responsivity of 4 A/W at 80K, and a peak detectivity of 4.510 cm·Hz½·W-1 was achieved at 80K at a reverse bias of 110 mV under 300 K 2(pi) FOV background. Some detectors showed a projected 0% cutoff wavelength up to 28~30 micrometers . The peak responsivity of 3Amp/Watt and detectivity of 4.2510 cm·Hz½·W-1 was achieved under -40mV reverse bias at 34K for these detectors. [reprint (PDF)]
 
18.  High performance monolithic, broadly tunable mid-infrared quantum cascade lasers
WENJIA Zhou, DONGHAI Wu, RYAN McCLINTOCK, STEVEN SLIVKEN, AND MANIJEH RAZEGH1
Optica 4(10), p. 1228-- October 10, 2017 ...[Visit Journal]
Mid-infrared lasers, emitting in the spectral region of 3-12 µm that contains strong characteristic vibrational tran­sitions of many important molecules, are highly desirable for spectroscopy sensing applications. High-efficiency quantum cascade lasers have been demonstrated with up to watt-level output power in the mid-infrared region. However, the wide wavelength tuning that is critical for spectroscopy applica­tions still largely relies on incorporating external gratings, which have stability issues. Here, we demonstrate a mono­lithic, broadly tunable quantum cascade laser source emitting between 6.1 and 9.2 µm through an on-chip integration of a sampled grating distributed feedback tunable laser array and a beam combiner. High peak power up to 65 mW has been obtained through a balanced high-gain active region design, efficient waveguide layout, and the development of a broad­band antireflection coating. Nearly fundamental transverse­mode operation is achieved for all emission wavelengths with a pointing stability better than 1.6 mrad (0.1 °). The demon­strated laser source opens new opportunities for mid-infrared spectroscopy. [reprint (PDF)]
 
18.  III-Nitride photon counting avalanche photodiodes
R. McClintock, J.L. Pau, K. Minder, C. Bayram and M. Razeghi
SPIE Conference, January 20-25, 2008, San Jose, CA Proceedings – Quantum Sensing and Nanophotonic Devices V, Vol. 6900, p. 69000N-1-11.-- February 1, 2008 ...[Visit Journal]
In order for solar and visible blind III-Nitride based photodetectors to effectively compete with the detective performance of PMT there is a need to develop photodetectors that take advantage of low noise avalanche gain. Furthermore, in certain applications, it is desirable to obtain UV photon counting performance. In this paper, we review the characteristics of III-nitride visible-blind avalanche photodetectors (APDs), and present the state-of-the-art results on photon counting based on the Geiger mode operation of GaN APDs. The devices are fabricated on transparent AlN templates specifically for back-illumination in order to enhance hole-initiated multiplication. The spectral response and Geiger-mode photon counting performance are analyzed under low photon fluxes, with single photon detection capabilities being demonstrated in smaller devices. Other major technical issues associated with the realization of high-quality visible-blind APDs and Geiger mode APDs are also discussed in detail and solutions to the major problems are described where available. Finally, future prospects for improving upon the performance of these devices are outlined. [reprint (PDF)]
 
18.  Substrate emission quantum cascade ring lasers with room temperature continuous wave operation
Y. Bai, S. Tsao, N. Bandyopadhyay, S. Slivken, Q.Y. Lu, and M. Razeghi
SPIE Proceedings, Vol. 8268, p. 82680N-- January 22, 2012 ...[Visit Journal]
We demonstrate room temperature, continuous wave operation of quantum cascade ring lasers around 5 μm with single mode operation up to 0.51 W output power. Single mode operation persists up to 0.4 W. Light is coupled out of the ring cavity through the substrate with a second order distributed feedback grating. The substrate emission scheme allows for epilayer-down bonding, which leads to room temperature continuous wave operation. The far field analysis indicates that the device operates in a high order mode. [reprint (PDF)]
 
18.  Novel Sb-based Alloys for Uncooled Infrared Photodetector Applications
M. Razeghi
SPIE Conference, San Jose, CA, -- January 22, 2001 ...[Visit Journal]
We report on the growth and characterization of InSbBi, InTlSb, InTlP, and the quaternary alloys for uncooled long- wavelength infrared photodetector applications. The layers were grown on InSb and GaAs substrates by low-pressure metalorganic chemical vapor deposition. The incorporation of Bi and Tl in InSb was investigated with high-resolution x-ray diffraction, energy dispersive x-ray analysis, and optical photoresponse measurements. We also demonstrate the photodetectors fabricated from the grown InSbBi and InTlSb alloys. InSb0.96Bi0.04 photoconductive detectors exhibited a responsivity of 3.2 V/W at 77 K. The estimated Johnson noise limited detectivity at 7 micrometers was 1.7 X 108 cm·Hz½/W at 77 K. A room temperature operating InSb0.95Bi0.05 photodetector was also demonstrated. Photoresponse up to 12 micrometers was achieved at 300 K. The responsivity and Johnson noise-limited detectivity at 10.6 μm were 1.9 mV/W and 1.2 X 106 cm·Hz½/W, respectively. Photoresponse up to 15 μm was achieved at 300 K from quaternary InTlAsSb and InBiAsSb alloys. [reprint (PDF)]
 
18.  Dark current suppression in Type-II InAs/GaSb superlattice long wavelength infrared photodiodes with M-structure barrier
B.M. Nguyen, D. Hoffman, P.Y. Delaunay, and M. Razeghi
Applied Physics Letters, Vol. 91, No. 16, p. 163511-1-- October 15, 2007 ...[Visit Journal]
We presented an alternative design of Type-II superlattice photodiodes with the insertion of a mid-wavelength infrared M-structure AlSb/GaSb/InAs/GaSb/AlSb superlattice for the reduction of dark current. The M-structure superlattice has a larger carrier effective mass and a greater band discontinuity as compared to the standard Type-II superlattices at the valence band. It acts as an effective medium that weakens the diffusion and tunneling transport at the depletion region. As a result, a 10.5 µm cutoff Type-II superlattice with 500 nm M-superlattice barrier exhibited a R0A of 200 cm2 at 77 K, approximately one order of magnitude higher than the design without the barrier. The quantum efficiency of such structures does not show dependence on either barrier thickness or applied bias. [reprint (PDF)]
 
18.  Broadband, Tunable, and Monolithic Quantum Cascade Lasers
M. Razeghi, Q. Y. Lu, N. Bandyopadhyay, W. Zhou, D. Heydari, Y. Bai, and S. Slivken.
Semiconductor lasers; (140.3600) Lasers, tunable-- May 19, 2017 ...[Visit Journal]
This article describes the state of research and recent developments related to broadband quantum cascade lasers. Monolithic tuning and system development is also discussed. [reprint (PDF)]
 
18.  Advances in UV sensitive visible blind GaN-based APDs
M. Ulmer, R. McClintock and M. Razeghi
SPIE Proceedings, San Francisco, CA (January 22-27, 2011), Vol. 7945, p. 79451G-- January 23, 2011 ...[Visit Journal]
In this paper, we describe our current state-of-the-art process of making visible-blind APDs based on GaN. We have grown our material on both conventional sapphire and low dislocation density free-standing c- and m-plane GaN substrates. Leakage current, gain, and single photon detection efficiency (SPDE) of these APDs are compared. The spectral response and Geiger-mode photon counting performance of UV APDs are studied under low photon fluxes. Single photon detection capabilities with over 30% are demonstrated. We show how with pulse height discrimination the Geiger-mode operation conditions can be optimized for enhanced SPDE versus dark counts. [reprint (PDF)]
 
18.  Recent advances in IR semiconductor laser diodes and future trends
M. Razeghi; Y. Bai; N. Bandyopadhyay; B. Gokden; Q.Y. Lu; S. Slivken
Photonics Society Summer Topical Meeting Series, IEEE [6000041], pp. 55-56 (2011)-- July 18, 2011 ...[Visit Journal]
The wall plug efficiency of the mid-infrared quantum cascade laser in room temperature continuous wave (cw) operation is brought to 21%, with a maximum output power of 5.1 W. Using a surface grating distributed feedback (DFB) approach, we demonstrated 2.4 W single mode output in room temperature cw operation. With a photonic crystal distributed feedback (PCDFB) design, we achieved single mode spectrum and close to diffraction limited far field with a room temperature high peak power of 34 W. [reprint (PDF)]
 
18.  Geiger-Mode Operation of AlGaN Avalanche Photodiodes at 255 nm
Lakshay Gautam, Alexandre Guillaume Jaud, Junhee Lee, Gail J. Brown, Manijeh Razeghi
Published in: IEEE Journal of Quantum Electronics ( Volume: 57, Issue: 2, April 2021) ...[Visit Journal]
We report the Geiger mode operation of back-illuminated AlGaN avalanche photodiodes. The devices were fabricated on transparent AlN templates specifically for back-illumination to leverage hole-initiated multiplication. The spectral response was analyzed with a peak detection wavelength of 255 nm with an external quantum efficiency of ~14% at zero bias. Low-photon detection capabilities were demonstrated in devices with areas 25 μm×25 μm. Single photon detection efficiencies of ~5% were achieved. [reprint (PDF)]
 
18.  Cubic Phase GaN on Nano-grooved Si (100) via Maskless Selective Area Epitaxy
Bayram, C., Ott, J. A., Shiu, K.-T., Cheng, C.-W., Zhu, Y., Kim, J., Razeghi, M. and Sadana, D. K.
Adv. Funct. Mater. 2014-- April 1, 2014 ...[Visit Journal]
A method of forming cubic phase (zinc blende) GaN (referred as c-GaN) on a CMOS-compatible on-axis Si (100) substrate is reported. Conventional GaN materials are hexagonal phase (wurtzite) (referred as h-GaN) and possess very high polarization fields (∼MV/cm) along the common growth direction of <0001>. Such large polarization fields lead to undesired shifts (e.g., wavelength and current) in the performance of photonic and vertical transport electronic devices. The cubic phase of GaN materials is polarization-free along the common growth direction of <001>, however, this phase is thermodynamically unstable, requiring low-temperature deposition conditions and unconventional substrates (e.g., GaAs). Here, novel nano-groove patterning and maskless selective area epitaxy processes are employed to integrate thermodynamically stable, stress-free, and low-defectivity c-GaN on CMOS-compatible on-axis Si. These results suggest that epitaxial growth conditions and nano-groove pattern parameters are critical to obtain such high quality c-GaN. InGaN/GaN multi-quantum-well structures grown on c-GaN/Si (100) show strong room temperature luminescence in the visible spectrum, promising visible emitter applications for this technology. [reprint (PDF)]
 
18.  Growth and characterization of InAs/GaSb photoconductors for long wavelength infrared range
H. Mohseni, E. Michel, J. Sandven, M. Razeghi, W. Mitchel, and G. Brown
Applied Physics Letters 71 (10)-- September 8, 1997 ...[Visit Journal]
In this letter we report the molecular beam epitaxial growth and characterization of InAs/GaSb superlattices grown on semi-insulating GaAs substrates for long wavelength infrared detectors. Photoconductive detectors fabricated from the superlattices showed photoresponse up to 12 µm and peak responsivity of 5.5 V/W with Johnson noise limited detectivity of 1.33 × 109 cm·Hz½/W at 10.3 µm at 78 K. [reprint (PDF)]
 
18.  Demonstration of a 256x256 Middle-Wavelength Infrared Focal Plane Array based on InGaAs/InGaP Quantum Dot Infrared Photodetectors (QDIPs)
J. Jiang, K. Mi, S. Tsao, W. Zhang, H. Lim, T.O'Sullivan, T. Sills, M. Razeghi, G.J. Brown, and M.Z. Tidrow
Virtual Journal of Nanoscale Science and Technology 9 (13)-- April 5, 2004 ...[Visit Journal][reprint (PDF)]
 
18.  Free-space optical communication using mid-infrared or solar-blind ultraviolet sources and detectors
R. McClintock, A. Haddadi and M. Razeghi
SPIE Proceedings, Vol. 8268, p. 826810-- January 22, 2012 ...[Visit Journal]
Free-space optical communication is a promising solution to the “last mile” bottleneck of data networks. Conventional near infrared-based free-space optical communication systems suffer from atmospheric scattering losses and scintillation effects which limit the performance of the data links. Using mid-infrared, we reduce the scattering and thus can improve the quality of the data links and increase their range. Because of the low scattering, the data link cannot be intercepted without a complete or partial loss in power detected by the receiver. This type of communications provides ultra-high bandwidth and highly secure data transfer for both short and medium range data links. Quantum cascade lasers are one of the most promising sources for mid-wavelength infrared sources and Type-II superlattice photodetectors are strong candidates for detection in this regime. The same way that that low scattering makes mid-wavelength infrared ideal for secure free space communications,high scattering can be used for secure short-range free-space optical communications. In the solar-blind ultraviolet (< 280 nm) light is strongly scattered and absorbed. This scattering makes possible non-line-of-sight free-space optical communications. The scattering and absorption also prevent remote eavesdropping. III-Nitride based LEDs and photodetectors are ideal for non-line-of-sight free-space optical communication. [reprint (PDF)]
 
18.  High power, high wall-plug efficiency, high reliability, continuous-wave operation quantum cascade lasers at Center for Quantum Devices
Razeghi, Manijeh
SPIE Proceedings Volume 11296, Optical, Opto-Atomic, and Entanglement-Enhanced Precision Metrology II; 112961C-- February 25, 2020 ...[Visit Journal]
Since the demonstration of the first quantum cascade laser (QCL) in 1997, QCLs have undergone considerable developments in output power, wall plug efficiency (WPE), beam quality, wavelength coverage and tunability. Among them, many world-class breakthroughs were achieved at the Center for Quantum Device at Northwestern University. In this paper, we will discuss the recent progress of our research and present the main contributions of the Center for Quantum Devices to the QCL family on high power, high wall-plug efficiency (WPE), continuous-wave (CW) and room temperature operation lasers. [reprint (PDF)]
 
18.  Effect of contact doping on superlattice-based minority carrier unipolar detectors
B.M. Nguyen, G. Chen, A.M. Hoang, S. Abdollahi Pour, S. Bogdanov, and M. Razeghi
Applied Physics Letters, Vol. 99, No. 3, p. 033501-1-- July 18, 2011 ...[Visit Journal]
We report the influence of the contact doping profile on the performance of superlattice-based minority carrier unipolar devices for mid-wave infrared detection. Unlike in a photodiode, the space charge in the p-contact of a pMp unipolar device is formed with accumulated mobile carriers, resulting in higher dark current in the device with highly doped p-contact. By reducing the doping concentration in the contact layer, the dark current is decreased by one order of magnitude. At 150 K, 4.9 μm cut-off devices exhibit a dark current of 2 × 10−5A/cm² and a quantum efficiency of 44%. The resulting specific detectivity is 6.2 × 1011 cm·Hz1/2/W at 150 K and exceeds 1.9 × 1014 cm·Hz1/2/W at 77 K. [reprint (PDF)]
 
18.  AlxGa1-xN (0 ≤ x ≤ 1) Ultraviolet Photodetectors Grown on Sapphire by Metal-organic Chemical-vapor Deposition
D. Walker, X. Zhang, A. Saxler, P. Kung, J. Xu, and M. Razeghi
Applied Physics Letters 70 (8)-- February 24, 1997 ...[Visit Journal]
AlxGa1–xN (0 ≤ x ≤ 1) ultraviolet photoconductors with cutoff wavelengths from 365 to 200 nm have been fabricated and characterized. The maximum detectivity reached 5.5 × 108 cm·Hz1/2/W at a modulating frequency of 14 Hz. The effective majority carrier lifetime in AlxGa1–xN materials, derived from frequency-dependent photoconductivity measurements, has been estimated to be from 6 to 35 ms. The frequency-dependent noise spectrum shows that it is dominated by Johnson noise at high frequencies for low-Al-composition samples. [reprint (PDF)]
 
18.  Investigation of surface leakage reduction for small pitch shortwave infrared photodetectors
Arash Dehzangi, Quentin Durlin, Donghai Wu, Ryan McClintock, Manijeh Razeghi
Semiconductor Science and Technology, 34(6), 06LT01-- May 25, 2019 ...[Visit Journal]
Different passivation techniques are investigated for reducing leakage current in small pixel (down to 9 μm) heterostructure photodetectors designed for the short-wavelength infrared range. Process evaluation test chips were fabricated using the same process as for focal plane arrays. Arrays of small photodetectors were electrically characterized under dark conditions from 150 K to room temperature. In order to evaluate the leakage current, we studied the relation between the inverse of dynamic resistance at −20 mV and zero bias and perimeter over area P/A ratio as the pixel size is scaled down. At 150 K, leakage current arising from the perimeter dominates while bulk leakage dominates at room temperature. We find that in shortwave devices directly underfilling hybridized devices with a thermoset epoxy resin without first doing any additional passivation/protection after etching gives the lowest leakage with a surface resistance of 4.2 × 109 and 8.9 × 103 Ω· cm−1 at 150 and 300 K, for −20 mV of bias voltage, respectively. [reprint (PDF)]
 
18.  High power, room temperature, Terahertz sources and frequency comb based on Difference frequency generation at CQD
Manijeh Razeghi
Proc. of SPIE 12230, 1223006, September 2022 ...[Visit Journal]
Quantum cascade laser (QCL) is becoming the leading laser source in the mid-infrared and terahertz range due to its rapid development in power, efficiency, and spectral covering range. Owing to its unique intersubband transition and fast carrier lifetime, QCL possesses strong nonlinear susceptibilities that makes it the ideal platform for a variety of nonlinear optical generations. Among this, terahertz (THz) source based on difference-frequency generation (DFG)and frequency comb based on four wave mixing effect are the most exciting phenomena which could potentially revolutionize spectroscopy in mid-infrared (mid-IR) and THz spectral range. In this paper, we will briefly discuss the recent progress of our research. This includes high power high efficiency QCLs, high power room temperature THz sources based on DFG-QCL, room temperature THz frequency comb, and injection locking of high-power QCL frequency combs. The developed QCLs are great candidates as next generation mid-infrared source for spectroscopy and sensing. [reprint (PDF)]
 
18.  Comparison of Trimethylgallium and Triethylgallium for the Growth of GaN
A. Saxler, D. Walker, P. Kung, X. Zhang, M. Razeghi, J. Solomon, W. Mitchel, and H.R. Vydyanath
Applied Physics Letters 71 (22)-- December 1, 1997 ...[Visit Journal]
GaN films grown by low-pressure metalorganic chemical vapor deposition using trimethylgallium and triethylgallium as gallium precursors are compared. The films were characterized by x-ray diffraction, Hall effect, photoluminescence, secondary ion mass spectroscopy, and etch pit density measurements. GaN layers grown using triethylgallium exhibited superior electrical and optical properties and a lower carbon impurity concentration. [reprint (PDF)]
 
18.  Continuous-wave operation of λ ~ 4.8 µm quantum-cascade lasers at room temperature
A. Evans, J.S. Yu, S. Slivken, and M. Razeghi
Applied Physics Letters, 85 (12)-- September 20, 2004 ...[Visit Journal]
Continuous-wave (cw) operation of quantum-cascade lasers emitting at λ~4.8 µm is reported up to a temperature of 323 K. Accurate control of layer thickness and strain-balanced material composition is demonstrated using x-ray diffraction. cw output power is reported to be in excess of 370 mW per facet at 293 K, and 38 mW per facet at 323 K. Room-temperature average power measurements are demonstrated with over 600 mW per facet at 50% duty cycle with over 300 mW still observed at 100% (cw) duty cycle. [reprint (PDF)]
 
18.  Type II superlattice infrared detectors and focal plane arrays
Vaidya Nathan; Manijeh Razeghi
Proc. SPIE 6542, Infrared Technology and Applications XXXIII, 654209 (May 14, 2007)-- May 14, 2007 ...[Visit Journal]
Type II superlattce photodetectors have recently experienced significant improvements in both theoretical structure design and experimental realization. Empirical Tight Binding Method is initiated and developed for Type II superlattice. Growth characteristics such as group V segregation and incorporation phenomena are taken into account in the model and shown higher precision. A new Type II structure, called M-structure, is introduced and theoretically demonstrated high R0A, high quantum efficiency. Device design is optimized to improve the performance. As a result, 55% quantum efficiency and 10 Ohm·cm² R0A are achieved for an 11.7 μm cut-off photodetector at 77K. FPA imaging at longwavelength is demonstrated with a capability of imaging up to 171K. At 81K, the noise equivalent temperature difference presented a peak at 0.33K. [reprint (PDF)]
 
17.  High-performance short-wavelength infrared photodetectors based on type-II InAs/InAs1-xSbx/AlAs1-xSbx superlattices
A. Haddadi, X.V. Suo, S. Adhikary, P. Dianat, R. Chevallier, A.M. Hoang, and M. Razeghi
Applied Physics Letters 107 , 141104-- October 5, 2015 ...[Visit Journal]
A high-performance short-wavelength infrared n-i-p photodiode based on InAs/InAs1-xSbx/AlAs1-xSbx type-II superlattices on GaSb substrate has been demonstrated. The device is designed to have a 50% cut-off wavelength of ~1.8μm at 300K. The photodetector exhibited a room-temperature (300 K) peak responsivity of 0.47 A/W at 1.6μm, corresponding to a quantum efficiency of 37% at zero bias under front-side illumination, without any anti-reflection coating. With an R×A of 285 Ω·cm² and a dark current density of 9.6×10-5 A/cm² under −50mV applied bias at 300 K, the photodiode exhibited a specific detectivity of 6.45×1010 cm·Hz½/W. At 200 K, the photodiode exhibited a dark current density of 1.3×10-8 A/cm² and a quantum efficiency of 36%, resulting in a detectivity of 5.66×1012 cm·Hz½/W. [reprint (PDF)]
 
17.  Quantum cascade lasers that emit more light than heat
Y. Bai, S. Slivken, S. Kuboya, S.R. Darvish and M. Razeghi
Nature Photonics, February 2010, Vol. 4, p. 99-102-- February 1, 2010 ...[Visit Journal]
For any semiconductor lasers, the wall plug efficiency, that is, the portion of the injected electrical energy that can be converted into output optical energy, is one of the most important figures of merit. A device with a higher wall plug efficiency has a lower power demand and prolonged device lifetime due to its reduced self-heating. Since its invention, the power performance of the quantum cascade laser has improved tremendously. However, although the internal quantum efficiency can be engineered to be greater than 80% at low temperatures, the wall plug efficiency of a quantum cascade laser has never been demonstrated above 50% at any temperature. The best wall plug efficiency reported to date is 36% at 120 K. Here, we overcome the limiting factors using a single-well injector design and demonstrate 53% wall plug efficiency at 40 K with an emitting wavelength of 5 µm. In other words, we demonstrate a quantum cascade laser that produces more light than heat. [reprint (PDF)]
 
17.  Highly selective two-color mid-wave and long-wave infrared detector hybrid based on Type-II superlattices
E.K. Huang, M.A. Hoang, G. Chen, S.R. Darvish, A. Haddadi, and M. Razeghi
Optics Letters, Vol. 37, No. 22, p. 4744-4746-- November 15, 2012 ...[Visit Journal]
We report a two-color mid-wave infrared (MWIR) and long-wave infrared (LWIR) co-located detector with 3 μm active region thickness per channel that is highly selective and can perform under high operating temperatures for the MWIR band. Under back-side illumination, a temperature evolution study of the MWIR detector’s electro-optical performance found the 300 K background-limit with 2π field-of-view to be achieved below operating temperatures of 160 K, at which the temperature’s 50% cutoff wavelength was 5.2 μm. The measured current reached the system limit of 0.1 pA at 110 K for 30 μm pixel-sized diodes. At 77 K, where the LWIR channel operated with a 50% cutoff wavelength at 11.2 μm, an LWIR selectivity of ∼17% was achieved in the MWIR wave band between 3 and 4.7 μm, making the detector highly selective. [reprint (PDF)]
 

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