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| 10. | Tunability of intersubband absorption from 4.5 to 5.3 µm in a GaN/Al0.2Ga0.8N superlattices grown by metalorganic chemical vapor deposition N. Péré-Laperne, C. Bayram, L. Nguyen-Thê, R. McClintock, and M. Razeghi Applied Physics Letters, Vol. 95, No. 13, p. 131109-- September 28, 2009 ...[Visit Journal] Intersubband (ISB) absorption at wavelengths as long as 5.3 µm is realized in GaN/Al0.2Ga0.8N superlattices grown by metalorganic chemical vapor deposition. By employing low aluminum content Al0.2Ga0.8N barriers and varying the well width from 2.6 to 5.1 nm, ISB absorption has been tuned from 4.5 to 5.3 µm. Theoretical ISB absorption and interband emission models are developed and compared to the experimental results. The effects of band offsets and the piezoelectric fields on these superlattices are investigated. [reprint (PDF)] |
| 10. | InTlSb alloys for infrared detection E. Bigan, Y.H. Choi, G. Labeyrie, and M. Razeghi Proceedings, SPIE Nonlinear Optics for High-Speed Electronics and Optical Frequency Conversion, Vol. 2145-- January 24, 1994 ...[Visit Journal] InTISb alloys have been grown by low-pressure metalorganic chemical vapor deposition, and characterized. Photoconductors exhibit a cutoff wavelength that can be tailored from 5.5 μm up to 9 μm by varying the thallium content. Experimental observations suggest that this can be further extended by increasing the thallium content. An InTISb photoconductor having a 9 μm cutoff wavelength exhibited a D* of 109 cm·Hz½·W-1 at 7 μm operating wavelength. [reprint (PDF)] |
| 10. | High‐purity GaAs layers grown by low‐pressure metalorganic chemical vapor deposition M. Razeghi; F. Omnes; J. Nagle; M. Defour; O. Acher; P. Bove Appl. Phys. Lett. 55, 1677–1679 (1989)-- October 16, 1989 ...[Visit Journal] We report electrical and optical properties of very high purity GaAs epilayers grown by low‐pressure metalorganic chemical vapor deposition using AsH3 and triethylgallium as As and Ga sources. An electron mobility of 335 000 cm2/V s at 38 K has been measured for a 12‐μ‐thick layer. [reprint (PDF)] |
| 10. | Electrically pumped photonic crystal distributed feedback quantum cascade lasers Y. Bai, S.R. Darvish, S. Slivken, P. Sung, J. Nguyen, A. Evans, W. Zhang, and M. Razeghi Applied Physics Letters, Vol. 91, No. 14, p. 141123-1-- October 1, 2007 ...[Visit Journal] We demonstrate electrically pumped, room temperature, single mode operation of photonic crystal distributed feedback (PCDFB) quantum cascade lasers emitting at ~4.75 µm. Ridge waveguides of 100 µm width were fabricated with both PCDFB and Fabry-Pérot feedback mechanisms. The Fabry-Pérot device has a broad emitting spectrum and a double lobed far-field character. The PCDFB device, as expected, has primarily a single spectral mode and a diffraction limited far field characteristic with a full angular width at half maximum of 2.4°. This accomplishment represents the first step in power scaling of single mode, midinfrared laser diodes operating at room temperature.
[reprint (PDF)] |
| 10. | Room temperature quantum cascade lasers with 27% wall plug efficiency Y. Bai, N. Bandyopadhyay, S. Tsao, S. Slivken and M. Razeghi Applied Physics Letters, Vol. 98, No. 18, p. 181102-1-- May 3, 2011 ...[Visit Journal] Using the recently proposed shallow-well design, we demonstrate InP based quantum cascade lasers (QCLs) emitting around 4.9 μm with 27% and 21% wall plug efficiencies in room temperature (298 K) pulsed and continuous wave (CW) operations, respectively. The laser core consists of 40 QCL-stages. The highest cw efficiency is obtained from a buried-ridge device with a ridge width of 8 μm and a cavity length of 5 mm. The front and back facets are antireflection and high-reflection coated, respectively. The maximum single facet cw power at room temperature amounts to 5.1 W. [reprint (PDF)] |
| 10. | InAsSb/InAsP strained-layer superlattice injection lasers operating at 4.0 μm grown by metal-organic chemical vapor deposition B. Lane, Z. Wu, A. Stein, J. Diaz, and M. Razeghi Applied Physics Letters 74 (23)-- June 7, 1999 ...[Visit Journal] We report high power mid-infrared electrical injection operation of laser diodes based on InAsSb/InAsP strained-layer superlattices grown on InAs substrate by metal-organic chemical vapor deposition. The broad-area laser diodes with 100 μm aperture and 1800 μm cavity length demonstrate peak output powers of 546 and 94 mW in pulsed and cw operation respectively at 100 K with a threshold current density as low as 100 A/cm². [reprint (PDF)] |
| 10. | Type-II superlattice-based heterojunction phototransistors for high speed applications Jiakai Li, Arash Dehzangi, Donghai Wu, Ryan McClintock, Manijeh Razeghi Infrared Physics and Technology 108, 1033502-- May 2, 2020 ...[Visit Journal] In this study, high speed performance of heterojunction phototransistors (HPTs) based on InAs/GaSb/AlSb type-II superlattice with 30 nm base thickness and 50% cut-off wavelength of 2.0 μm at room temperature are demonstrated. We studied the relationship between -3 dB cut-off frequency of these HPT versus mesa size, applied bias, and collector layer thickness. For 8 μm diameter circular mesas HPT devices with a 0.5 μm collector layer, under 20 V applied bias voltage, we achieved a -3 dB cut-off frequency of 2.8 GHz.
[reprint (PDF)] |
| 10. | GaN-based nanostructured photodetectors J.L. Pau, C. Bayram, P. Giedraitis, R. McClintock, and M. Razeghi SPIE Proceedings, San Jose, CA Volume 7222-14-- January 26, 2009 ...[Visit Journal] The use of nanostructures in semiconductor technology leads to the observation of new phenomena in device physics. Further quantum and non-quantum effects arise from the reduction of device dimension to a nanometric scale. In nanopillars, quantum confinement regime is only revealed when the lateral dimensions are lower than 50 nm. For larger mesoscopic systems, quantum effects are not observable but surface states play a key role and make the properties of nanostructured devices depart from those found in conventional devices. In this work, we present the fabrication of GaN nanostructured metal-semiconductor-metal (MSM) and p-i-n photodiodes (PIN PDs) by e-beam lithography, as well as the investigation of their photoelectrical properties at room temperature. The nanopillar height and diameter are about 520 nm and 200 nm, respectively. MSMs present dark currents densities of 0.4 A/cm2 at ±100 V. A strong increase of the optical response with bias is observed, resulting in responsivities higher than 1 A/W. The relationship between this gain mechanism and surface states is discussed. PIN PDs yield peak responsivities (Rpeak) of 35 mA/W at -4 V and show an abnormal increase of the response (Rpeak > 100 A/W) under forward biases. [reprint (PDF)] |
| 10. | High‐quality GaAs/Ga0.49In0.51P superlattices grown on GaAs and silicon substrates by low‐pressure metalorganic chemical vapor deposition Available M. Razeghi; Ph. Maurel; F. Omnes; M. Defour; C. Boothroyd; W. M. Stobbs; M. Kelly J. Appl. Phys. 63, 4511–4514 (1988) -- May 1, 1988 ...[Visit Journal] We report the successful growth of Ga0.49 Iuo.5 ! P-GaAs superlattices on GaAs and Si
substrates by low-pressure metalorganic chemical vapor deposition. The high quality of the
structure grown on GaAs and silicon substrates has been evidenced by transmission electron
microscopy photographs, that show very sharp interfaces between GaAs wells and
Gao.49InO.51 P barriers, with perfect control of thicknesses and compositions. Classical Hall
measurements performed on the sample further demonstrated the presence of a twodimensional electron ga.<; with a mobility at T = 4 K , fL (4 K) = 50000 cm2
1V Is, and a carrier
concentration n _ (4 K) = 2,9 X 1011 em -2. GaAs/Gao.49 InO.
51 P superlattices have been used,
as well as buffer layer in order to grow GaAs on silicon substrates. Mirrorlike single-crystal
GaAs has thus been obtained. A GaInP IGaAs heterostructure with electron HaH mobility as
high as 6000 cm2
/V Is at 300 K and 80000 cm2
/V Is at 4 K has been grown, which is the
highest mobility that has yet been reported for these materials, [reprint (PDF)] |
| 10. | Metalorganic chemical vapor deposition of monocrystalline GaN thin films on β-LiGaO2substrates P. Kung, A. Saxler, X. Zhang, D. Walker, R. Lavado, and M. Razeghi Applied Physics Letters 69 (14)-- September 30, 1996 ...[Visit Journal] We report the metalorganic chemical vapor deposition growth and characterization of monocrystalline GaN thin films on β-LiGaO2 substrates. The influence of the growth temperature on the crystal quality was studied. The structural, electrical, and optical properties of the films were assessed through scanning electron microscopy, x-ray diffraction, Hall measurements, optical transmission, photoluminescence. [reprint (PDF)] |
| 10. | Schottky MSM Photodetectors on GaN Films Grown on Sapphire by Lateral Epitaxial Overgrowth P. Kung, D. Walker, P. Sandvik, M. Hamilton, J. Diaz, I.H. Lee and M. Razeghi SPIE Conference, San Jose, CA, -- January 27, 1999 ...[Visit Journal] We report the growth and characterization of Schottky based metal-semiconductor-metal ultraviolet photodetectors fabricated on lateral epitaxially overgrown GaN films. The lateral epitaxial overgrowth of GaN was carried out on basal plane sapphire substrates by low pressure metalorganic chemical vapor deposition and exhibited lateral growth rates more than 5 times as high as vertical growth rates. The spectral responsivity, the dependence on bias voltage, on incident optical power, and the time response of these photodetectors have been characterized. Two detector orientations were investigated: one with the interdigitated finger pattern parallel and the other perpendicular to the underlying SiOx mask stripes. [reprint (PDF)] |
| 10. | Persistent photoconductivity in Ga0.49In0.51P/GaAs heterojunctions S. Ben Amor; L. Dmowski; J. C. Portal; N. J. Pulsford; R. J. Nicholas; J. Singleton; M. Razeghi J. Appl. Phys. 65, 2756–2760 (1989-- November 18, 1988 ...[Visit Journal] We have studied the persistent photoconductivity (PPC) effect in Ga0.49 Ino.
sl P IGaAs
heterostructures. Through time- and temperature-dependent Hall effect, we observe very small
relaxation rates and the PPC remains observable at room temperature. Optical experiments
show an optical energy threshold of 1.15 e V and an infrared quenching of the ppc. Thermal
cycling of the samples strongly affects the PPC and the quenching temperature. The center
responsible for the observed PPC, therefore, appears related to defects, Most of our
observations are qualitatively understood in a large lattice relaxation DX-like center approach.
However, the origin of the high quenching temperature remains to be explained. [reprint (PDF)] |
| 10. | Electrically pumped photonic crystal distributed feedback quantum cascade lasers Y. Bai, P. Sung, S.R. Darvish, W. Zhang, A. Evans, S. Slivken, and M. Razeghi SPIE Conference, January 20-25, 2008, San Jose, CA Proceedings – Quantum Sensing and Nanophotonic Devices V, Vol. 6900, p. 69000A-1-8.-- February 1, 2008 ...[Visit Journal] We demonstrate electrically pumped, room temperature, single mode operation of photonic crystal distributed feedback (PCDFB) quantum cascade lasers emitting at ~ 4.75 µm. Ridge waveguides of 50 µm and 100 µm width were fabricated with both PCDFB and Fabry-Perot feedback mechanisms. The Fabry-Perot device has a broad emitting spectrum and a broad far-field character. The PCDFB devices have primarily a single spectral mode and a diffraction limited far field characteristic with a full angular width at half-maximum of 4.8 degrees and 2.4 degrees for the 50 µm and 100 µm ridge widths, respectively.
[reprint (PDF)] |
| 10. | High-Performance Type-II InAs/GaSb Superlattice Photodiodes with Cutoff Wavelength Around 7 µm Y. Wei, A. Hood, H. Yau, V. Yazdanpanah, M. Razeghi, M.Z. Tidrow and V. Nathan Applied Physics Letters, 86 (9)-- February 28, 2005 ...[Visit Journal] We report the most recent result in the area of type-II InAs/GaSb superlattice photodiodes that have a cutoff wavelength around 7 µm at 77 K. Superlattice with a period of 40 Å lattice matched to GaSb was realized using GaxIn1–x type interface engineering technique. Compared with significantly longer period superlattices, we have reduced the dark current density under reverse bias dramatically. For a 3 µm thick structure, using sulfide-based passivation, the dark current density reached 2.6×10–5 A/cm2 at –3 V reverse bias at 77 K. At this temperature the photodiodes have R0A of 9300 Ω·cm2 and a thermally limited zero bias detectivity of 1×1012 cm·Hz½/W. The 90%–10% cutoff energy width was only 16.5 meV. The devices did not show significant dark current change at 77 K after three months storage in the atmosphere. [reprint (PDF)] |
| 10. | Molecular Beam Epitaxial Growth of High Quality InSb for p-i-n Photodetectors G. Singh, E. Michel, C. Jelen, S. Slivken, J. Xu, P. Bove, I. Ferguson, and M. Razeghi Journal of Vacuum Science and Technology B, 13 (2)-- March 1, 1995 ...[Visit Journal] The InSb infrared photodetectors grown heteroepitaxially on Si substrates by molecular beam epitaxy (MBE) are reported. Excellent InSb material quality is obtained on 3-inch Si substrates (with a GaAs predeposition) as confirmed by structural, optical, and electrical analysis. InSb infrared photodetectors on Si substrates that can operate from 77 K to room temperature have been demonstrated. The peak voltage-responsitivity at 4 μm is about 1.0×103 V/W and the corresponding Johnson-noise-limited detectivity is calculated to be 2.8×1010 cm·Hz½/W. This is the first important stage in developing InSb detector arrays or monolithic focal plane arrays (FPAs) on silicon. The development of this technology could provide a challenge to traditional hybrid FPA's in the future. [reprint (PDF)] |
| 10. | Radiometric characterization of long-wavelength infrared type II strained layer superlattice focal plane array under low-photon irradiance conditions J. Hubbs, V. Nathan, M. Tidrow, and M. Razeghi Optical Engineering, Vol. 51, No. 6, p. 064002-1-- June 15, 2012 ...[Visit Journal] We present the results of the radiometric characterization of an “M” structure long wavelength infrared Type-II strained layer superlattice(SLS) infrared focal plane array (IRFPA) developed by Northwestern University (NWU). The performance of the M-structure SLS IRFPA was
radiometrically characterized as a function of photon irradiance, integration time, operating temperature, and detector bias. Its performance is
described using standard figures of merit: responsivity, noise, and noise equivalent irradiance. Assuming background limited performance operation at higher irradiances, the detector quantum efficiency for the SLS detector array is approximately 57%. The detector dark density at 80 K
is 142 μA∕cm², which represents a factor of seven reduction from previously measured devices. [reprint (PDF)] |
| 10. | Improved performance of quantum cascade lasers via manufacturable quality epitaxial side down mounting process utilizing aluminum nitride heatsinks A. Tsekoun, R. Go, M. Pushkarsky, M. Razeghi, C.K.N. Patel SPIE Conference, San Jose, CA, Vol. 6127, pp. 612702-- January 23, 2006 ...[Visit Journal] We report substantially improved performance of high power quantum cascade lasers by utilizing epi-side down mounting that provides superior heat dissipation properties. We have obtained CW power output of 450 mW at 20°C from mid-IR QCLs. The improved thermal management achieved with epi-side down mounting has also permitted us to carry out initial lifetime tests on the mid-IR QCLs. No degradation of power output is seen even after over 300 hours of CW operation at 25°C with power output in excess of 300 mW. We believe these improvements should permit incorporation of mid-IR QCLs in reliable instrumentation. [reprint (PDF)] |
| 10. | High Performance Type-II InAs/GaSb Superlattice Photodiodes H. Mohseni, Y. Wei, and M. Razeghi SPIE Conference, San Jose, CA, -- January 22, 2001 ...[Visit Journal] We report on the demonstration of high performance p-i-n photodiodes based on Type-II InAs/GaSb superlattices operating in the very long wavelength infrared (VLWIR) range at 80 K. Material is grown by molecular beam epitaxy on GaSb substrates with excellent crystal quality as evidenced by x-ray diffraction and atomic force microscopy. The processed devices with a 50% cutoff wavelength of λc equals 22 μm show a peak current responsivity about 5.5 A/W at 80 K. The use of binary layers in the superlattice has significantly enhanced the uniformity and reproducibility of the energy gap. The 90% to 10% cut-off energy width of these devices is on the order of 2 kT which is about four times smaller compared to the devices based on InAs/Ga1-xInxSb superlattices. Similar photovoltaic devices with cut-off wavelengths up to 25 μm have been measured at 80 K. Our experimental results shows excellent uniformity over a three inch wafer area, indicating the possibility of VLWIR focal plane arrays based on Type-II superlattices. [reprint (PDF)] |
| 10. | Ultraviolet Detector Materials and Devices Studied by Femtosecond Nonlinear Optical Techniques M. Wraback, H. Shen, P. Kung, M. Razeghi, J.C. Carrano, T. Li, and J.C. Campbell SPIE Conference, San Jose, CA, -- January 26, 2000 ...[Visit Journal] Femtosecond nonlinear optical techniques have been employed in the study of carrier dynamics and transport in UV detector materials. Visible femtosecond pulses derived from the signal beam of a 250 kHz regenerative amplifier-pumped optical parametric amplifier were frequency doubled to obtain pulses tunable from 250 nm to 375 nm. Time-resolved reflectivity experiments indicate that the room-temperature carrier lifetime in GaN grown by double lateral epitaxial overgrowth is about 3 times longer than that of GaN grown on sapphire without benefit of this technique. The electron velocity-field characteristics and saturation velocity in GaN have been obtained form time-resolved studies of electroabsorption in a GaN p-i-n diode. The peak steady- state velocity of 1.9x107 cm/s in this device occurs at 225 kV/cm. Time-resolved transmission measurements have been used to monitor ultrafast carrier relaxation phenomena in a thin AlGaN layer with bandgap in the solar blind region of the spectrum. Excitation intensity and wavelength dependent studies of the photoinduced bleaching decays suggest that they are primarily governed by trapping in a high density of sub-bandgap defect levels. [reprint (PDF)] |
| 10. | Quantum oscillations at a Ga0.47In0.53AsInP heterojunction interface R.J Nicholas a, M.A Brummell a , J.C Portal b, M Razeghi c, M.A Poisson R.J Nicholas, M.A Brummell, J.C Portal, M Razeghi, M.A Poisson, Quantum oscillations at a Ga0.47In0.53AsInP heterojunction interface, Solid State Communications, Volume 43, Issue 11, 1982, Pages 825-828,-- September 1, 1982 ...[Visit Journal] We report the observation of a two dimensional gas of high mobility electrons at the interface of a Ga0.47In0.53AsInP heterojunction grown by MOCVD. The two dimensional electron concentrations and effective mass are determined by Shubnikov-de Haas studies, and compared with theoretical predictions. Evidence of an enhancement of the g-factor is observed. We also report observations of very pronounced quantum Hall steps as seen in GaAs-GaAlAs heterojunctions.
[reprint (PDF)] |
| 10. | Room temperature continuous wave, monolithic tunable THz sources based on highly efficient mid-infrared quantum cascade lasers Quanyong Lu, Donghai Wu, Saumya Sengupta, Steven Slivken, Manijeh Razeghi Nature Scientific Reports 6, Article number: 23595-- March 24, 2016 ...[Visit Journal] A compact, high power, room temperature continuous wave terahertz source emitting in a wide frequency range (ν ~ 1–5 THz) is of great importance to terahertz system development for applications in spectroscopy, communication, sensing, and imaging. Here, we present a strong-coupled strain-balanced quantum cascade laser design for efficient THz generation based on intracavity difference frequency generation. Room temperature continuous wave emission at 3.41 THz with a side-mode suppression ratio of 30 dB and output power up to 14 μW is achieved with a wall-plug efficiency about one order of magnitude higher than previous demonstrations. With this highly efficient design, continuous wave, single mode THz emissions with a wide frequency tuning range of 2.06–4.35 THz and an output power up to 4.2 μW are demonstrated at room temperature from two monolithic three-section sampled grating distributed feedback-distributed Bragg reflector lasers. [reprint (PDF)] |
| 10. | Sharp/Tuneable UVC Selectivity and Extreme Solar Blindness in Nominally Undoped Ga2O3 MSM Photodetectors Grown by Pulsed Laser Deposition D. J. Rogers, A. Courtois, F. H. Teherani, V. E. Sandana, P. Bove, X. Arrateig, L. Damé, P. Maso, M. Meftah, W. El Huni, Y. Sama, H. Bouhnane, S. Gautier, A. Ougazzaden & M. Razeghi Proc. SPIE 11687 (2021) 116872D-1 ...[Visit Journal] Ga2O3layers were grown on c-sapphire substrates by pulsed laser deposition. Optical transmission spectra were coherent with a bandgap engineering from 4.9 to 6.2 eV controlled via the growth conditions. X-ray diffraction revealed that the films were mainly β-Ga2O3(monoclinic) with strong (-201) orientation. Metal-Semiconductor-Metal photodetectors based on gold/nickel Inter- Digitated-Transducer structures were fabricated by single-step negative photolithography. 240 nm peak response sensors gave over 2 orders-of-magnitude of separation between dark and light signal with state-of-the-art solar and visible rejection ratios ((I240 : I290) of > 3 x 105 and (I240 : I400) of > 2 x 106) and dark signals of <50 pA (at a bias of -5V). Spectral responsivities showed an exceptionally narrow linewidth (16.5 nm) and peak values exhibited a slightly superlinear increase with applied bias up to a value of 6.5 A/W (i.e. a quantum efficiency of > 3000%) at 20V bias. [reprint (PDF)] |
| 10. | Single-mode, high-power, midinfrared, quantum cascade laser phased arrays Wenjia Zhou , Donghai Wu , Quan-Yong Lu, Steven Slivken & Manijeh Razeghi Scientific Reports 8:14866-- October 5, 2018 ...[Visit Journal] We demonstrate single-mode, 16-channel, optical phased arrays based on quantum cascade laser
technology, with emission wavelengths around 4.8 μm. The integrated device consists of a distributed feedback seed section, a highly-efficient tree array multi-mode interferometer power splitter, and a 16-channel amplifier array with a 4° angled facet termination. With a single layer Y2O3 coating, the
angled facet reflectivity is estimated to be less than 0.1% for suppressing amplifier self-lasing. A peak output power of 30 W is achieved with an emission spectrum narrower than 11 nm and a side mode suppression ratio over 25 dB. Far field distribution measurement result indicates a uniform phase distribution across the array output. Using the same phased array architecture, we also demonstrate single-mode 3.8 μm QCL amplifier arrays with up to 20 W output power. [reprint (PDF)] |
| 10. | Metalorganic chemical vapor deposition of undoped In1−xAlxAs on InP M. A. di Forte‐Poisson; M. Razeghi; J. P. Duchemin M. A. di Forte‐Poisson, M. Razeghi, J. P. Duchemin; Metalorganic chemical vapor deposition of undoped In1−xAlxAs on InP. J. Appl. Phys. 1 December 1983; 54 (12): 7187–7189. https://doi.org/10.1063/1.331956-- December 1, 1983 ...[Visit Journal] In1−x Alx As epitaxial layers were grown on (100) InP substrates by the organometallic vapor phase epitaxy method. Undoped layers with mirror smooth surfaces were obtained for substrate temperatures of 600–650 °C. By adjusting the relative ratio of In and Al, lattice matched In0.52 Al0.48 As epilayers were reproducibly grown on InP substrates. X‐ray measurements, scanning Auger analyses, and electron mobilities are presented. These results show that the quality of the epilayers obtained here was comparable to the best reported layers grown by other methods. [reprint (PDF)] |
| 10. | Intersubband hole absorption in GaAs-GaInP Quantum Wells grown by Gas Source Molecular Beam Epitaxy J. Hoff, C. Jelen, S. Slivken, E. Michel, O. Duchemin, E. Bigan, and M. Razeghi with G. Brown and S.M. Hegde (Wright Laboratory) Applied Physics Letters 65 (9)-- August 29, 1994 ...[Visit Journal] P-doped GaAs‐GaInP quantum wells have been grown on GaAs substrate by gas source molecular beam epitaxy. Structural quality has been evidenced by x-ray diffraction. A narrow low-temperature photoluminescence full width at half‐maximum has been measured. Strong hole intersubband absorption has been observed at 9 μm, and its dependence on light polarization has been investigated. [reprint (PDF)] |
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