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26.  Optoelectronic Devices Based on III-V Compound Semiconductors Which Have Made a Major Scientific and Technological Impact in the Past 20 Years
M. Razeghi
IEEE Journal of Selected Topics in Quantum Electronics 6 (6), pp.1344 - 1354 -- November 1, 2000 ...[Visit Journal]
This paper reviews some of our pioneering contributions to the field of III–V compound semiconductor materials and low-dimensional optoelectronic devices. These contributions span from the ultraviolet (200 nm) up to the far-infrared (25 μm) portion of the electromagnetic spectrum and have had a major scientific and technological impact on the semiconductor world in the past 20 years. [reprint (PDF)]
 
26.  Electro-thermal breakdown in p-NiO/n-Ga2O3 heterojunction power diodes: evidence for the role of heat extraction via sapphire
S. Kubsky, Z. Berger, M. Chevrot, D. J. Rogers, V. E. Sandana, F. Hosseini Teherani, N. De France, M. Lesecq, Z. Bougrioua, M. Razeghi
Proc. of SPIE Vol. PC13897, PC138970X · 2026 ...[Visit Journal]
Gallium oxide (Ga₂O₃) is attracting strong interest for next-generation power electronics due to its ultra-wide bandgap and large critical breakdown field; however, device performance is frequently constrained by self-heating arising from its relatively low and anisotropic thermal conductivity. In this work, the electrical and thermal behaviour of p-NiO/n-Ga₂O₃ heterojunction diodes grown by pulsed laser deposition on r-plane sapphire substrates is investigated under high-bias operation. Identical ring-mesa devices were mounted either on a thermally insulating support or on a metal heat sink, enabling a direct comparison of electro-thermal behaviour. While both configurations exhibit rectifying I–V characteristics, heat-sunk devices show reduced surface temperature rise, suppressed reverse leakage, and a significantly higher breakdown voltage (~ +2150 V) compared with devices measured without effective heat extraction (~ +1600 V). The results demonstrate that electro-thermal runaway, rather than intrinsic junction limitations, governs breakdown in these thin-film Ga₂O₃ heterojunctions, highlighting thermal management and thermal boundary conditions as key design parameters for high-voltage Ga₂O₃ power devices. [reprint (PDF)]
 
26.  Recent advances of terahertz quantum cascade lasers
Manijeh Razeghi
Proc. SPIE 8119, Terahertz Emitters, Receivers, and Applications II, 81190D (September 07, 2011)-- November 7, 2011 ...[Visit Journal]
In the past decade, tremendous development has been made in GaAs/AlGaAs based THz quantum cascade laser (QCLs), however, the maximum operating temperature is still limited below 200 K (without magnetic field). THz QCL based on difference frequency generation (DFG) represents a viable technology for room temperature operation. Recently, we have demonstrated room temperature THz emission (∼ 4 THz) up to 8.5 μW with a power conversion efficiency of 10 μW/W². A dual-period distributed feedback grating is used to filter the mid-infrared spectra in favor of an extremely narrow THz linewidth of 6.6 GHz. [reprint (PDF)]
 
26.  Modeling of Type-II InAs/GaSb Superlattices Using Empirical Tight-Binding Method and Interface Engineering
Y. Wei and M. Razeghi
Physical Review B, 69 (8)-- February 15, 2004 ...[Visit Journal]
We report the most recent work on the modeling of type-II InAs/GaSb superlattices using the empirical tight binding method in an sp3s* basis. After taking into account the antimony segregation in the InAs layers, the modeling accuracy of the band gap has been improved. Our calculations agree with our experimental results within a certain growth uncertainty. In addition, we introduce the concept of GaxIn1-x type interface engineering in order to reduce the lattice mismatch between the superlattice and the GaSb (001) substrate to improve the overall superlattice material quality. [reprint (PDF)]
 
26.  Pulse Autocorrelation Measurements Based on Two- and Three-Photon Conductivity in a GaN Photodiode
A. Streltsov, K.D. Moll, A. Gaeta, P. Kung, D. Walker, and M. Razeghi
Applied Physics Letters 75 (24)-- December 13, 1999 ...[Visit Journal]
We characterize the performance of a GaN p-i-n photodiode as a nonlinear sensor for second- and third-order femtosecond pulse autocorrelation measurements in the visible and near-infrared regimes, respectively. The two- and three-photon absorption coefficients for GaN are also determined. [reprint (PDF)]
 
26.  High performance bias-selectable three-color Short-wave/Mid-wave/Long-wave Infrared Photodetectors based on Type-II InAs/GaSb/AlSb superlattices
Anh Minh Hoang, Arash Dehzangi, Sourav Adhikary, & Manijeh Razeghi
Nature Scientific Reports 6, Article number: 24144-- April 7, 2016 ...[Visit Journal]
We propose a new approach in device architecture to realize bias-selectable three-color shortwave-midwave-longwave infrared photodetectors based on InAs/GaSb/AlSb type-II superlattices. The effect of conduction band off-set and different doping levels between two absorption layers are employed to control the turn-on voltage for individual channels. The optimization of these parameters leads to a successful separation of operation regimes; we demonstrate experimentally three-color photodiodes without using additional terminal contacts. As the applied bias voltage varies, the photodiodes exhibit sequentially the behavior of three different colors, corresponding to the bandgap of three absorbers. Well defined cut-offs and high quantum efficiency in each channel are achieved. Such all-in-one devices also provide the versatility of working as single or dual-band photodetectors at high operating temperature. With this design, by retaining the simplicity in device fabrication, this demonstration opens the prospect for three-color infrared imaging. [reprint (PDF)]
 
26.  GalnAs AND GaInAsP MATERIALS GROWN BY LOW PRESSURE MOCVD FOR MICROWAVE AND OPTOELECTRONIC APPLICATIONS
J.P. Duchemin, J.P. Hirtz, M. Razeghi, M. Bonnet , S.D. Hersee
J.P. Duchemin, J.P. Hirtz, M. Razeghi, GaInAs and GaInAsP materials grown by low pressure MOCVD for microwave and optoelectronic applications, Journal of Crystal Growth, 55, 1, 1981, Pages 64-73,-- August 1, 1981 ...[Visit Journal]
The low pressure MOCVD technique has been successfully used to grow GaInAsP, lattice-matched to InP, for the complete compositional range between InP (λ=0.91 μm) and the ternary compound Ga0.47In0.53As (λ=1.67 μm). By contrast to LPE growth it has been found that during the MOCVD growth of double heterostructures InP can be grown directly onto the ternary or quaternary with no disturbance of the active layer, i.e. there is no effect equivalent to “melt back”. The compositional grading on both sides of the active layer was measured by scanning Auger spectroscopy on bevelled samples. It was found that the graded regions were typically less than 100 Å wide for GaInAsP active layers and less than 50 Å wide for GaInAs active layers. Single layers of undoped GaInAs exhibited a typical mobility of 6700 cm2 V-1s-1 at 1.5×1017 cm-3. The compositional uniformity of the ternary layers was characterised by measurement of the photoluminescence wavelength at various points on a large sample. The wavelength varied by <3 nm over 95% of the area, which was approximately 8 cm2. Our early MOCVD grown GaInAsP/InP DH lasers exhibited high thresholds due to a poor interface between the p-InP and the active layer. However, recently fabricated broad area lasers emitting at 1.27 μm show an average threshold current density of 1.5 kA cm-2 with a T0 of between 70 to 80 K. Stripe geometry lasers have being fabricated from this material and CW operation has been obtained. [reprint (PDF)]
 
26.  

-- November 30, 1999
 
25.  Multi-band SWIR-MWIR-LWIR Type-II superlattice based infrared photodetector
Manijeh Razeghi, Arash Dehzangi, Jiakai Li
Results in Optics Volume 2, January 2021, 100054 https://doi.org/10.1016/j.rio.2021.100054 ...[Visit Journal]
Type-II InAs/GaSb superlattices (T2SLs) has drawn a lot of attention since it was introduced in 1970, especially for infrared detection as a system of multi-interacting quantum wells. In recent years, T2SL material system has experienced incredible improvements in material quality, device structure designs and device fabrication process, which elevated the performances of T2SL-based photo-detectors to a comparable level to the state-of-the-art material systems for infrared detection such as Mercury Cadmium Telluride (MCT). As a pioneer in the field, center for quantum devices (CQD) has been involved in growth, design, characterization, and introduction of T2SL material system for infrared photodetection. In this review paper, we will present the latest development of bias-selectable multi-band infrared photodetectors at the CQD, based on InAs/GaSb/AlSb and InAs/InAs1-xSbx type-II superlattice. [reprint (PDF)]
 
25.  Future of AlxGa1-xN Materials and Device Technology for Ultraviolet Photodetectors
P. Kung, A. Yasan, R. McClintock, S. Darvish, K. Mi, and M. Razeghi
SPIE Conference, San Jose, CA, Vol. 4650, pp. 199-- May 1, 2002 ...[Visit Journal]
Design of the photodetector structure is one of the key issues in obtaining high performance devices; especially the thickness of the intrinsic region for p-i-n photodiodes is a crucial value and needs to be optimized. We compare the performance of the p-i-n photodiodes with different widths for the depletion region, which shows a trade-off between speed and responsivity of the devices. [reprint (PDF)]
 
25.  High Performance InAs/GaSb Superlattice Photodiodes for the Very Long Wavelength Infrared Range
H. Mohseni, M. Razeghi, G.J. Brown, Y.S. Park
Applied Physics Letters 78 (15)-- April 9, 2001 ...[Visit Journal]
We report on the demonstration of high-performance p-i-n photodiodes based on type-II InAs/GaSb superlattices with 50% cut-off wavelength λc = 16 μm operating 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 show a current responsivity of 3.5 A/W at 80 K leading to a detectivity of ∼ 1.51×1010 cm·Hz½/W. The quantum efficiency of these devices is about 35% which is comparable to HgCdTe detectors with a similar active layer thickness. [reprint (PDF)]
 
25.  Interface-induced Suppression of the Auger Recombination in Type-II InAs/GaSb Superlattices
H. Mohseni, V.I. Litvinov and M. Razeghi
Physical Review B 58 (23)-- December 15, 1998 ...[Visit Journal]
The temperature dependence of the nonequilibrium carriers lifetime has been deduced from the measurement of the photocurrent response in InAs/GaSb superlattices. Based on the temperature dependence of the responsivity and modeling of the transport parameters we have found that the carrier lifetime weakly depends on temperature in the high-temperature region. This indicates the temperature dependence of the Auger recombination rate with no threshold that differs it from that in the bulk material and can be attributed to the interface-induced suppression of the Auger recombination in thin quantum wells. [reprint (PDF)]
 
25.  High Optical Response in Forward Biased (In,Ga)N-GaN Multiquantum-Well Diodes Under Barrier Illumination
J.L. Pau, R. McClintock, C. Bayram, K. Minder, D. Silversmith and M. Razeghi
IEEE Journal of Quantum Electronics, Vol. 44, No. 4, p. 346-353.-- April 1, 2008 ...[Visit Journal]
The authors report on the current–voltage (I–V) characteristic under forward biases obtained in low leakage, small size p-(In,Ga)N–GaN-n multiquantum well diodes. Under barrier illumination, the devices present a high optical response with capabilities to detect optical powers in the pW range without further amplification. This response is attributed to the screening of the internal electric fields. Recombination times of a few seconds are found to be associated to this mechanism. Moreover, a step-like feature is found in the I– V characteristic before the diode turn-on voltage. Our model proposes tunneling current through the multi-quantum-well structure as responsible of this feature. Fast modulation of the tunneling effect under barrier illumination is used to evaluate the detection of low photon fluxes. [reprint (PDF)]
 
25.  Low Noise Short Wavelength Infrared Avalanche Photodetector Using SB-Based Strained Layer Superlattice
Arash Dehzangi, Jiakai Li, Manijeh Razeghi
Photonics 2021, 8(5), 148; https://doi.org/10.3390/photonics8050148 Received: 8 March 2021 / Revised: 12 April 2021 / Accepted: 25 April 2021 / Published: 30 April 2021 ...[Visit Journal]
We demonstrate low noise short wavelength infrared (SWIR) Sb-based type II superlattice (T2SL) avalanche photodiodes (APDs). The SWIR GaSb/(AlAsSb/GaSb) APD structure was designed based on impact ionization engineering and grown by molecular beam epitaxy on a GaSb substrate. At room temperature, the device exhibits a 50% cut-off wavelength of 1.74 µm. The device was revealed to have an electron-dominated avalanching mechanism with a gain value of 48 at room temperature. The electron and hole impact ionization coefficients were calculated and compared to give a better prospect of the performance of the device. Low excess noise, as characterized by a carrier ionization ratio of ~0.07, has been achieved. [reprint (PDF)]
 
25.  Room Temperature, Continuous Wave Quantum Cascade Laser Grown Directly on a Si Wafer
Steven Slivken and Manijeh Razeghi
S. Slivken and M. Razeghi,, Journal of Quantum Electronics, Vol. 59, No. 4, doi: 10.1109/JQE.2023.3282710 ...[Visit Journal]
We report the room temperature demonstration of a high power, continuous wave, LWIR quantum cascade laser grown directly on a Si substrate. A new wafer, based on a high efficiency, strain-balanced laser core was processed into a lateral injection buried heterostructure laser geometry. A pulsed efficiency of 11.1% was demonstrated at room temperature, with an emission wavelength of 8.35 μm. With low fidelity, epilayer-up packaging, CW emission up to 343 K was also demonstrated, with a maximum output power of >0.7 W near room temperature. [reprint (PDF)]
 
25.  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)]
 
25.  Aluminum free GaInP/GaAs Quantum Well Infrared Photodetectors for Long Wavelength Detection
C. Jelen, S. Slivken, J. Hoff, M. Razeghi, and G. Brown
Applied Physics Letters 70 (3)-- January 20, 1997 ...[Visit Journal]
We demonstrate quantum well infrared photodetectors based on a GaAs/Ga0.51In0.49P superlattice structure grown by gas-source molecular beam epitaxy. Wafers were grown with varying well widths. Wells of 40, 65, and 75 Å resulted in peak detection wavelengths of 10.4, 12.8, and 13.3 μm with a cutoff wavelength of 13.5, 15, and 15.5 μm, respectively. The measured peak and cutoff wavelengths match those predicted by eight band theoretical analysis. Measured dark currents were lower than equivalent GaAs/AlGaAs samples. [reprint (PDF)]
 
25.  Type-II InAs/GaSb superlattice photovoltaic detectors with cutoff wavelength approaching 32 μm
Y. Wei, A. Gin, M. Razeghi and G.J. Brown
Applied Physics Letters, 81 (19)-- November 4, 2002 ...[Visit Journal]
We report the most recent advance in the area of type-II InAs/GaSb superlattice photovoltaic detectors that have cutoff wavelengths beyond 25 μm, with some at nearly 32 μm. The photodiodes with a heterosuperlattice junction showed Johnson noise limited peak detectivity of 1.05 x 1010 cm Hz½/W at 15 μm under zero bias, and peak responsivity of 3 A/W under -40 mV reverse bias at 34 K illuminated by ~300 K background with a 2π field-of-view. The maximum operating temperature of these detectors ranges from 50 to 65 K. No detectable change in the blackbody response has been observed after 5-6 thermal cyclings, with temperature varying between 15 and 296 K in vacuum. [reprint (PDF)]
 
25.  Room Temperature Terahertz and Frequency Combs Based on Intersubband Quantum Cascade Laser Diodes: History and Future
Manijeh Razeghi , and Quanyong Lu
Photonics 2025, 12(1), 79; ...[Visit Journal]
: The year 2024 marks the 30-year anniversary of the quantum cascade laser (QCL), which is becoming the leading laser source in the mid-infrared (mid-IR) range. Since the first demonstration, QCL has undergone tremendous development in terms of the output power, wall plug efficiency, spectral coverage, wavelength tunability, and beam quality. Owing to its unique intersubband transition and fast gain features, QCL possesses strong nonlinearities that makes it an ideal platform for nonlinear photonics like terahertz (THz) difference frequency generation and direct frequency comb generation via fourwave mixing when group velocity dispersion is engineered. The feature of broadband, high-power, and low-phase noise of QCL combs is revolutionizing mid-IR spectroscopy and sensing by offering a new tool measuring multi-channel molecules simultaneously in the µs time scale. While THz QCL difference frequency generation is becoming the only semiconductor light source covering 1–5 THz at room temperature. In this paper, we will introduce the latest research from the Center for Quantum Devices at Northwestern University and briefly discuss the history of QCL, recent progress, and future perspective of QCL research, especially for QCL frequency combs, room temperature THz QCL difference frequency generation, and major challenges facing QCL in the future. [reprint (PDF)]
 
25.  Aluminum-free Quantum Well Intersubband Photodetectors with p-type GaAs Wells and lattice-matched ternary and quaternary barriers
J. Hoff, E. Bigan, G.J. Brown, and M. Razeghi
Optoelectronic Integrated Circuit Materials, Physics and Devices, SPIE Conference, San Jose, CA; Proceedings, Vol. 2397-- February 6, 1995 ...[Visit Journal]
Acceptor doped Quantum Well Intersubband Photodetectors with GaAs wells and lattice matched barriers of both ternary (In0.49Ga0.51P) and quaternary (In0.62Ga0.38As0.22P0.78) materials have been grown on semi-insulating GaAs substrates by Low Pressure Metal Organic Chemical Vapor Deposition. Mesa devices were fabricated and subjected to a series of tests to illuminate experimentally some of the detection capabilities of the lattice matched quaternary InxGa1-xAsyP1-y system with (0 ≤ x ≤ 0.52) and (0 ≤ y ≤ 1). The observed photoresponse cut-off wavelengths are in good agreement with the activation energies observed in the temperature dependence of the dark currents. Kronig-Penney calculations were used to model the intersubband transition energies. [reprint (PDF)]
 
24.  High-Average-Power, High-Duty-Cycle (~6 μm) Quantum Cascade Lasers
S. Slivken, A. Evans, J. David, and M. Razeghi
Virtual Journal of Nanoscience & Technology 9-- December 9, 2002 ...[Visit Journal][reprint (PDF)]
 
24.  Novel process for direct bonding of GaN onto glass substrates using sacrificial ZnO template layers to chemically lift-off GaN from c-sapphire
Rogers, D. J.; Ougazzaden, A.; Sandana, V. E.; Moudakir, T.; Ahaitouf, A.; Teherani, F. Hosseini; Gautier, S.; Goubert, L.; Davidson, I. A.; Prior, K. A.; McClintock, R. P.; Bove, P.; Drouhin, H.-J.; Razeghi, M.
Proc. SPIE 8263, Oxide-based Materials and Devices III, 82630R (February 9, 2012)-- February 9, 2012 ...[Visit Journal]
GaN was grown on ZnO-buffered c-sapphire (c-Al2O3) substrates by Metal Organic Vapor Phase Epitaxy. The ZnO then served as a sacrificial release layer, allowing chemical lift-off of the GaN from the c-Al2O3 substrate via selective wet etching of the ZnO. The GaN was subsequently direct-wafer-bonded onto a glass substrate. X-Ray Diffraction, Scanning Electron Microscopy, Energy Dispersive X-ray microanalysis, Room Temperature Photoluminescence & optical microscopy confirmed bonding of several mm2 of crack-free wurtzite GaN films onto a soda lime glass microscope slide with no obvious deterioration of the GaN morphology. Using such an approach, InGaN based devices can be lifted-off expensive single crystal substrates and bonded onto supports with a better cost-performance profile. Moreover, the approach offers the possibility of reclaiming and reusing the substrate. [reprint (PDF)]
 
24.  Use of Yttria-Stabilised Zirconia Substrates for Zinc Oxide Mediated Epitaxial Lift-off of Superior Yttria-Stabilised Zirconia Thin Films
D. J. Rogers, T. Maroutian, V. E. Sandana, P. Lecoeur, F. H. Teherani, P. Bove and M. Razeghi
Proc. of SPIE Vol. 12887, Oxide-based Materials and Devices XV, 128870P 2024, San Francisco),doi: 10.1117/12.3023431 ...[Visit Journal]
ZnO layers were grown on (100) and (111) oriented YSZ substrates by pulsed laser deposition (PLD). X-ray diffraction studies revealed growth of wurtzite ZnO with strong preferential (0002) orientation. The ZnO layer on YSZ (111) showed distinct Pendellosung fringes and a more pronounced c-axis orientation (rocking curve of 0.08°). Atomic force microscopy revealed RMS roughnesses of 0.7 and 2.2nm for the ZnO on the YSZ (111) and YSZ (100), respectively. YSZ was then grown on the ZnO buffered YSZ (111) substrate by PLD. XRD revealed that the YSZ overlayer grew with a strong preferential (111) orientation. The YSZ/ZnO/YSZ (111) top surface was temporary bonded to an Apiezon wax carrier and the sample was immersed in 0.1M HCl so as to preferentially etch/dissolve away the ZnO underlayer and release the YSZ from the substrate. XRD revealed only the characteristic (111) peak of YSZ after lift-off and thus confirmed both the dissolution of the ZnO and the preservation of the crystallographic integrity of the YSZ on the wax carrier. Optical and Atomic Force Microscopy revealed some buckling, roughening and cracking of the lifted YSZ, however. XRD suggested that this may have been due to compressive epitaxial strain release. [reprint (PDF)]
 
24.  Imprinting of Nanoporosity in Lithium-Doped Nickel Oxide through the use of Sacrificial Zinc Oxide Nanotemplates
Vinod E. Sandana, David J. Rogers, Ferechteh H. Teheran1, Philippe Bove, Ryan McClintock and Manijeh Razeghi
Proc. SPIE 10105, Oxide-based Materials and Devices VIII, 101052C-- April 3, 2017 ...[Visit Journal]
Methods for simultaneously increasing the conductivity and the porosity of NiO layers grown by pulsed laser deposition (PLD) were investigated in order to develop improved photocathodes for p-DSSC applications. NiO:Li (20at%) layers grown on c-Al2O3 by PLD showed a sharp drop in conductivity with increasing substrate temperature. Layers grown at room temperature were more than two orders of magnitude more conductive than undoped NiO layers but did not show evidence of any porosity in Scanning Electron Microscope (SEM) images. A new method for imposing a nanoporosity in NiO was developed based on a sacrificial template of nanostructured ZnO. SEM images and EDX spectroscopy showed that a nanoporous morphology had been imprinted in the NiO overlayer after preferential chemical etching away of the nanostructured ZnO underlayer. Beyond p-DSSC applications, this new process could represent a new paradigm for imprinting porosity in a whole range of materials. [reprint (PDF)]
 
24.  Gas Source Molecular Beam Epitaxy Growth and Characterization of Ga0.51In0.49P/InxGa1-xAs/GaAs Modulation-doped Field-effect Transistor Structures
C. Besikci, Y. Civan, S. Ozder, O. Sen, C. Jelen, S. Slivken, and M. Razeghi
Semiconductor Science Technology 12-- January 1, 1997 ...[Visit Journal]
Lattice-matched Ga0.51In0.49P/GaAs and strained Ga0.51In0.49P/InxGa1−xAs/GaAs (0.1 ≤ x ≤ 0.25) modulation-doped field-effect transistor structures were grown by gas source molecular beam epitaxy by using Si as dopant. Detailed electrical characterization results are presented. The Ga0.5In0.49P/In0.25Ga0.75As/GaAs sample yielded dark two-dimensional electron gas densities of 3.75 x 1012 cm-2 (300 K) and 2.3 x 1012 cm-2 (77 K) which are comparable to the highest sheet electron densities reported in AlGaAs/InGaAs/GaAs and InAlAs/InGaAs/InP modulation-doped heterostructures. Persistent photoconductivity was observed in the strained samples only. A 0.797 eV deep level has been detected in the undoped GaInP layers of the structures. Another level, with DLTS peak height dependent on the filling pulse width, has been detected at the interface of the strained samples. Based on the DLTS and Hall effect measurement results, this level, which seems to be the origin of persistent photoconductivity, can be attributed to the strain relaxation related defects. [reprint (PDF)]
 

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