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19 May 1997

Volume 70, Issue 20, pp. 2641-2767

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Improved mobility of amorphous silicon thin-film transistors deposited by hot-wire chemical vapor deposition on glass substrates

V. Chu, J. Jarego, H. Silva, T. Silva, M. Reissner, P. Brogueira, and J. P. Conde

Appl. Phys. Lett. 70, 2714 (1997); http://dx.doi.org/10.1063/1.119001 (3 pages) | Cited 12 times

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High quality thin-film transistors (TFTs) with hydrogenated amorphous silicon, a-Si:H, deposited by hot-wire chemical vapor deposition as the active layer at growth rates above 20 Å/s, have been prepared using a standard, low-temperature process on glass substrates. These TFTs show a switching ratio above 3×106, a threshold voltage of 6 V, a subthreshold slope of 1.7 V/decade, and a field effect mobility of 0.1 cm2 V−1 s1. © 1997 American Institute of Physics.
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85.30.Tv Field effect devices
81.05.Gc Amorphous semiconductors
85.40.Sz Deposition technology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Observation of biexcitonic effect in single ZnCdSe quantum well under very low excitation density

G. Kuang, W. Gebhardt, E. Griebl, K. Sube, M. Kastner, M. Wörz, and T. Reisinger

Appl. Phys. Lett. 70, 2717 (1997); http://dx.doi.org/10.1063/1.119002 (3 pages) | Cited 9 times

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Under an excitation density of 0.4 W/cm2, a strong biexcitonic peak was observed in the photoluminescence (PL) spectrum of a single quantum well which was grown in submonolayer deposition mode. Its intensity was found to increase superlinearly with excitation density. The shape of the biexcitonic peak was found to be similar to that of biexcitons in CuCl and CdS crystal and a binding energy of 9.8 meV was obtained. When the temperature increased from 10 to 31 K, the biexcitonic peak decreased considerably whereas the excitonic peak increased slightly. © 1997 American Institute of Physics.
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71.35.Gg Exciton-mediated interactions
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors

Metalorganic vapor-phase epitaxy of cubic AlxGa1−xN alloy on a GaAs (100) substrate

Atsushi Nakadaira and Hidenao Tanaka

Appl. Phys. Lett. 70, 2720 (1997); http://dx.doi.org/10.1063/1.119003 (3 pages) | Cited 20 times

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Cubic AlxGa1−xN was grown on a GaAs (100) substrate by using low-pressure metalorganic vapor-phase epitaxy with a GaN buffer layer grown at low and high temperatures. The high-growth–temperature GaN layer improved the quality of the cubic AlxGa1−xN. Also, the AlN molar fraction could be controlled by changing the carrier gas flow of trimethylaluminum. The AlxGa1−xN epitaxial layers in the range of 0 ⩽ x ⩽ 0.23 exhibited strong near-band-edge photoluminescence at room temperature. Their photoluminescence peak energies show a linear dependence on the molar fraction. © 1997 American Institute of Physics.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.05.Dz II-VI semiconductors
78.55.Cr III-V semiconductors

Positron annihilation in ZnSe layers grown on GaAs: Zinc vacancies and drift in the electric field at the ZnSe/GaAs interface

L. Liszkay, C. Corbel, P. Hautojärvi, R. Aulombard, T. Cloître, J. Griesche, and F. Kiessling

Appl. Phys. Lett. 70, 2723 (1997); http://dx.doi.org/10.1063/1.119004 (3 pages) | Cited 4 times

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We used a slow positron beam to investigate the depth dependence of the positron–electron pair momentum distribution in ZnSe layers grown on a GaAs substrate. We report evidence that positrons annihilate in lattice in undoped ZnSe and at vacancies in heavily n-type ZnSe. It is also demonstrated that positrons in semi-insulating ZnSe are drifted to GaAs by fields of 1–3 kV/cm. © 1997 American Institute of Physics.
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78.70.Bj Positron annihilation
61.72.J- Point defects and defect clusters
81.05.Dz II-VI semiconductors

A step-free InAs quantum well selectively grown on a GaAs (111)B substrate

Toshio Nishida and Naoki Kobayashi

Appl. Phys. Lett. 70, 2726 (1997); http://dx.doi.org/10.1063/1.119005 (3 pages) | Cited 1 time

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By combining finite-area selective growth and surface stoichiometry control, a step-free InAs quantum well was successfully obtained. An InAs/GaAs quantum-well structure was selectively grown by metalorganic vapor phase epitaxy on a GaAs (111)B substrate masked by a SiO2 pattern. A 100 nm thick and 8 μm diameter step-free GaAs buffer layer was grown at 800 °C and a step-free monolayer of InAs was grown on this surface at 650 °C. To eliminate indium segregation during the capping procedure, the InAs layer was buried by GaAs under a stable As-rich condition. The formation of a step-free InAs monolayer quantum well was confirmed by ex situ atomic force microscopy, and this observation was also supported by spatially resolved photoluminescence measurement. © 1997 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.05.Ea III-V semiconductors
68.35.Ct Interface structure and roughness

Electrical and structural analysis of high-dose Si implantation in GaN

J. C. Zolper, H. H. Tan, J. S. Williams, J. Zou, D. J. H. Cockayne, S. J. Pearton, M. Hagerott Crawford, and R. F. Karlicek

Appl. Phys. Lett. 70, 2729 (1997); http://dx.doi.org/10.1063/1.119254 (3 pages) | Cited 57 times

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For the development of ion implantation processes for GaN to advanced devices, it is important to understand the dose dependence of impurity activation along with implantation-induced damage generation and removal. We find that Si implantation in GaN can achieve 50% activation at a dose of 1×1016 cm−2, despite significant residual damage after the 1100 °C activation anneal. The possibility that the generated free carriers are due to implantation damage alone and not Si-donor activation is ruled out by comparing the Si results to those for implantation of the neutral species Ar. Ion channeling and cross-sectional transmission electron microscopy are used to characterize the implantation-induced damage both as implanted and after a 1100 °C anneal. Both techniques confirm that significant damage remains after the anneal, which suggests that activation of implanted Si donors in GaN doses not require complete damage removal. However, an improved annealing process may be needed to further optimize the transport properties of implanted regions in GaN. © 1997 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.uj III-V and II-VI semiconductors
85.40.Ry Impurity doping, diffusion and ion implantation technology
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Thermally oxidized AlN thin films for device insulators

E. A. Chowdhury, J. Kolodzey, J. O. Olowolafe, G. Qiu, G. Katulka, D. Hits, M. Dashiell, D. van der Weide, C. P. Swann, and K. M. Unruh

Appl. Phys. Lett. 70, 2732 (1997); http://dx.doi.org/10.1063/1.118980 (3 pages) | Cited 10 times

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The structural, optical, and electronic properties of an insulating material prepared by the thermal oxidation of AlN thin films on Si have been studied by a number of different experimental techniques. The thermal oxidation at 1100 °C of reactively sputtered AlN films on Si wafers was found to result in the formation of an oxide with a relative Al to O concentration near Al2O3 with small amounts of incorporated N. The structure of the AlO:N oxide could be varied between amorphous and polycrystalline, depending on the preparation conditions, and the oxide surface was found to be approximately three time smoother than the as-sputtered AlN films. Metal–oxide–silicon capacitors had an oxide charge density of about 1011 cm−2, capacitance–voltage characteristics similar to pure SiO2, and a dielectric constant of 12.4. Infrared measurements yielded a refractive index of 3.9. These results indicate that thermally oxidized AlN films show promise as insulating structures for many integrated circuit applications, particularly for the case of III–V and group III–nitride based semiconductors. © 1997 American Institute of Physics.
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81.65.Mq Oxidation
81.05.Ea III-V semiconductors
77.55.-g Dielectric thin films
68.55.-a Thin film structure and morphology

High quality crystalline ZnO buffer layers on sapphire (001) by pulsed laser deposition for III–V nitrides

R. D. Vispute, V. Talyansky, Z. Trajanovic, S. Choopun, M. Downes, R. P. Sharma, T. Venkatesan, M. C. Woods, R. T. Lareau, K. A. Jones, and A. A. Iliadis

Appl. Phys. Lett. 70, 2735 (1997); http://dx.doi.org/10.1063/1.119006 (3 pages) | Cited 97 times

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ZnO thin films with near perfect crystallinity have been grown epitaxially on sapphire (001) by pulsed laser deposition technique. The ω-rocking curve full width at half-maximum of the ZnO(002) peak for the films grown at 750 °C, oxygen pressure 10−5 Torr was 0.17°. The high degree of crystallinity was confirmed by ion channeling technique providing a minimum Rutherford backscattering yield of 2%–3% in the near-surface region ( ∼ 2000 Å). The atomic force microscopy revealed smooth hexagonal faceting of the ZnO films. It has been possible to deposit epitaxial AlN films of thickness 1000 Å on epi-ZnO/sapphire. Excellent crystalline properties of these epi-ZnO/sapphire heterostructures are, thus, promising for lattice-matched substrates for III–V nitride heteroepitaxy and optoelectronics devices. © 1997 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Fg Pulsed laser ablation deposition
81.05.Dz II-VI semiconductors
81.05.Ea III-V semiconductors

InAs self-organized quantum dashes grown on GaAs (211)B

S. P. Guo, H. Ohno, A. Shen, F. Matsukura, and Y. Ohno

Appl. Phys. Lett. 70, 2738 (1997); http://dx.doi.org/10.1063/1.119007 (3 pages) | Cited 21 times

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We have grown InAs self-organized quantum dots and quantum dashes on GaAs (211)B substrates by molecular beam epitaxy. The growth temperature dependence of InAs nanostructures were studied by in situ reflection high-energy electron diffraction (RHEED) and ex situ atomic force microscopy. In the studied temperature range from 400 to 510 °C, the RHEED pattern changed from streaky to spotty after deposition of 6 ML of InAs, showing the formation of nanostructures. The quantum dots grown at lower growth temperatures (from 400 to 490 °C) showed bimodal dot size distribution. At higher growth temperatures, a drastic change from quantum dots to quantum dashes was observed. The quantum dashes have an asymmetric hutlike shape and align themselves along the [011] direction. The quantum dash width increases dramatically, whereas the average length and density increases slightly on further deposition of InAs. © 1997 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy

Effects of aquaregia treatment of indium–tin–oxide substrates on the behavior of double layered organic light-emitting diodes

F. Li, H. Tang, J. Shinar, O. Resto, and S. Z. Weisz

Appl. Phys. Lett. 70, 2741 (1997); http://dx.doi.org/10.1063/1.119008 (3 pages) | Cited 71 times

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The effects of a controlled aquaregia treatment of indium–tin–oxide (ITO) substrates on the behavior of highly efficient vacuum evaporated double layered 8-tris-hydroxyquinoline Al (Alq3)-based light-emitting diodes are described. It is found that in suitably treated devices, both current injection and the electroluminescence (EL) are significantly enhanced. The enhancement is believed to result from the greater ITO/hole transporting layer contact areas and the contact conditions. The observed dependence of I(V), the EL output, and the EL efficiency on the ITO surface morphology indicates that space-charge-limited currents dominate the behavior of the devices. © 1997 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.66.Qn Polymers; organic compounds
42.70.Jk Polymers and organics

External gettering by aluminum–silicon alloying observed from carrier recombination at dislocations in float zone silicon wafers

S. Martinuzzi, I. Perichaud, and J. J. Simon

Appl. Phys. Lett. 70, 2744 (1997); http://dx.doi.org/10.1063/1.119009 (3 pages) | Cited 8 times

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The influence of external gettering by a backside aluminum–silicon (Al–Si) alloy on the recombination strength of dislocation arrays in silicon was investigated. These arrays were made by scratching and bending float zone silicon wafers at 750 °C for 6 h. Light beam induced current maps showed that the recombination strength of these defects is drastically reduced at room temperature after the sample have been submitted to an external gettering treatment by means of Al–Si alloying at 900 °C. This can be explained by the removal of metallic impurities introduced by inadvertent contamination from dislocations and by their capture in the aluminum–silicon alloy by means of a segregation induced gettering mechanism. © 1997 American Institute of Physics.
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61.72.Yx Interaction between different crystal defects; gettering effect
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.05.Cy Elemental semiconductors

Nanopatterning organic monolayers on Si(100) by selective chemisorption of norbornadiene

G. C. Abeln, S. Y. Lee, J. W. Lyding, D. S. Thompson, and J. S. Moore

Appl. Phys. Lett. 70, 2747 (1997); http://dx.doi.org/10.1063/1.119010 (3 pages) | Cited 26 times

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Norbornadiene (bicyclo[2.2.1]Hepta-2,5-diene) is shown to chemisorb selectivity at room temperature onto clean Si(100)-2×1 surfaces. Combining the chemoselectivity of this process with scanning tunneling microscope nanolithography allows the formation of nanometer-sized regions having a norbonadiene adlayer. This concept could serve as the basis for creating spatially resolved templates to initiate chemical reactions with other chemical species in the presence of hydrogen-passivated Si(100)-2×1 areas. © 1997 American Institute of Physics.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
07.79.Cz Scanning tunneling microscopes

Fabrication of high mobility in situ back-gated (311)A hole gas heterojunctions

M. Y. Simmons, A. R. Hamilton, S. J. Stevens, D. A. Ritchie, M. Pepper, and A. Kurobe

Appl. Phys. Lett. 70, 2750 (1997); http://dx.doi.org/10.1063/1.119012 (3 pages) | Cited 9 times

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Using an n-type (311)A GaAs substrate we have fabricated in situ back-gated GaAs/(Al,Ga)As hole gases with mobilities of μ = 1.1×106 cm2 V−1 s−1 at 30 mK. We have investigated both experimentally and theoretically the scattering mechanisms that limit the mobility in both the [math33] and [01math] directions. Using a combination of front and back gates to keep the carrier density constant, we can distinguish between scattering mechanisms which are primarily dependent on the carrier density and those that are sensitive to the shape of the hole wave function. This approach also eliminates complications arising from the variations of the Fermi surface anisotropy with carrier density. Our data confirms that anisotropic interface roughness scattering, arising from the nature of the (311)A GaAs surface, is the dominant scattering mechanism at carrier densities down to ps = 5.0×1010 cm−2. © 1997 American Institute of Physics.
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72.20.Fr Low-field transport and mobility; piezoresistance
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Subband emissions of InGaN multi-quantum-well laser diodes under room-temperature continuous wave operation

Shuji Nakamura, Masayuki Senoh, Shin-ichi Nagahama, Naruhito Iwasa, Takao Yamada, Toshio Matsushita, Yasunobu Sugimoto, and Hiroyuki Kiyoku

Appl. Phys. Lett. 70, 2753 (1997); http://dx.doi.org/10.1063/1.118973 (3 pages) | Cited 55 times

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The emission spectra of InGaN multi-quantum-well (MQW) laser diodes (LDs) under continuous-wave (CW) operation at room temperature (RT) showed periodic subband emissions with an energy separation of 2 meV. The peak wavelength of the laser emission was measured as a function of the operating current. The peak wavelength showed mode hopping toward higher energy with increasing operating current. Each single-mode laser emission was located at a peak of each periodic subband emission. These periodic subband emissions probably result from the transitions between the subband energy levels of the InGaN quantum dots formed from In-rich regions in the InGaN well layers. High-power InGaN MQW LDs with an output power of 40 mW were performed under RT CW operation. © 1997 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Pk Continuous operation

High-sensitivity ferromagnetic resonance measurements on micrometer-sized samples

S. Zhang, S. A. Oliver, N. E. Israeloff, and C. Vittoria

Appl. Phys. Lett. 70, 2756 (1997); http://dx.doi.org/10.1063/1.118974 (3 pages) | Cited 11 times

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Ferromagnetic resonance measurements were taken on a 4 μm diam disk using a planar microwave transmission line device. The absorption modes of a sample placed on this device can be measured by monitoring the microwave power transmitted across the device while a swept magnetic field varies the sample absorption through resonance. Results for the disk, which was etched from a 105 nm thick amorphous Fe80B15Si5 film, followed the Kittel model over the frequency range from 2 to 20 GHz, in agreement with parameters measured on 5 mm diam disks by a microwave cavity. These results indicate the device has a sensitivity of 3×109⋅ΔH spins, almost two orders of magnitude better than microwave cavity measurements. © 1997 American Institute of Physics.
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76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.50.Kj Amorphous and quasicrystalline magnetic materials

Observation of a Coulomb staircase in electron transport through a molecularly linked chain of gold colloidal particles

T. Sato and H. Ahmed

Appl. Phys. Lett. 70, 2759 (1997); http://dx.doi.org/10.1063/1.118975 (3 pages) | Cited 35 times

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Submonolayer gold colloidal particles were deposited by using aminosilane [3-(2-aminoethylamino)propyltrimethoxysilane] as an adhesion agent on the substrate. It was observed that these submonolayer particles transform themselves into short chains of a few gold colloidal particles after a subsequent dithiol (1,6-hexanedithiol) treatment and an additional gold colloidal particle deposition. These chains bridged a gap that was formed between source and drain metal electrodes defined by electron beam lithography; thus realizing a quasi one dimensional current path between the source and drain. The device exhibited a clear Coulomb staircase at both 4.2 and 77 K. © 1997 American Institute of Physics.
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73.23.Hk Coulomb blockade; single-electron tunneling
85.35.Gv Single electron devices
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices

Spatio-temporal imaging of voltage pulses with an ultrafast scanning tunneling microscope

Jacob R. Jensen, Ulrich D. Keil, and Jørn M. Hvam

Appl. Phys. Lett. 70, 2762 (1997); http://dx.doi.org/10.1063/1.118976 (3 pages) | Cited 7 times

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Measurements on an ultrafast scanning tunneling microscope with simultaneous spatial and temporal resolution are presented. We show images of picosecond pulses propagating on a coplanar waveguide and resolve their mode structures. The influence of transmission line discontinuities on the mode structure is investigated. It is also demonstrated how common and differential modes of electrical pulses are generated. The capacitive coupling between the tip and the transmission line is explained in terms of two contributions: a long range and a local coupling. We also show how these contributions affect the imaging of the propagating pulses. © 1997 American Institute of Physics.
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07.79.Cz Scanning tunneling microscopes
84.40.Az Waveguides, transmission lines, striplines
06.60.Jn High-speed techniques (microsecond to femtosecond)
FREE

Comment on “Ground-state exciton lasing in CdSe submonolayers inserted in a ZnSe matrix” [Appl. Phys. Lett. 69, 1343 (1996)]

K. P. O’Donnell and Ulrike Woggon

Appl. Phys. Lett. 70, 2765 (1997); http://dx.doi.org/10.1063/1.118977 (1 page) | Cited 4 times

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Abstract Unavailable
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78.66.Hf II-VI semiconductors
71.35.Gg Exciton-mediated interactions
FREE

Response to “Comment on ‘Ground state exciton lasing in CdSesubmonolayers inserted in a ZnSe matrix’ ” [Appl. Phys.Lett. 70, 2765 (1997)]

N. N. Ledentsov, I. L. Krestnikov, M. V. Maximov, S. V. Ivanov, S. L. Sorokin, P. S. Kop’ev, Zh. I. Alferov, D. Bimberg, and C. M. Sotomayor Torres

Appl. Phys. Lett. 70, 2766 (1997); http://dx.doi.org/10.1063/1.119266 (2 pages) | Cited 20 times

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78.66.Hf II-VI semiconductors
71.35.Gg Exciton-mediated interactions
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