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27 Mar 2000

Volume 76, Issue 13, pp. 1641-1784

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Evidence of localization effects in InGaN single-quantum-well ultraviolet light-emitting diodes

S. F. Chichibu, K. Wada, J. Müllhäuser, O. Brandt, K. H. Ploog, T. Mizutani, A. Setoguchi, R. Nakai, M. Sugiyama, H. Nakanishi, K. Korii, T. Deguchi, T. Sota, and S. Nakamura

Appl. Phys. Lett. 76, 1671 (2000); http://dx.doi.org/10.1063/1.126131 (3 pages) | Cited 29 times

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The importance of doping or alloying with In for obtaining high external quantum efficiency was shown for GaN-based single-quantum-well (SQW) structures in terms of localization effects due to quantum-disk (Q-disk [M. Sugawara, Phys. Rev. B 51, 10743 (1995)])-size potential minima in the QW plane. The ultraviolet light-emitting diode with lightly In-alloyed InGaN SQW exhibited an electroluminescence peak from the band-tail states. Monochromatic cathodoluminescence mapping images of In0.03Ga0.97N SQW indicated the presence of Q-disk-size effective bandgap variation. Furthermore, cubic InGaN QW which does not suffer from the piezoelectric field normal to the QW plane, also exhibited a broad band-tail. © 2000 American Institute of Physics.
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85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
78.60.Fi Electroluminescence
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.35.Gg Exciton-mediated interactions
78.60.Hk Cathodoluminescence, ionoluminescence
78.66.Fd III-V semiconductors
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Influence of gas flow stoichiometry on the luminescence of organometallic-vapor-phase-grown ZnxCd1−xSe epilayers

X. B. Zhang and S. K. Hark

Appl. Phys. Lett. 76, 1674 (2000); http://dx.doi.org/10.1063/1.126132 (3 pages) | Cited 1 time

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ZnxCd1−xSe epilayers were grown by organometallic vapor phase epitaxy using various VI/II flow ratios at a temperature of 420 °C. Cathodoluminescence (CL) spectroscopy and imaging were used to study their luminescent properties. Both near-band gap emissions (NBE) and deep-level emissions (DLE) were found in the CL spectra. We found that the width of the NBE peak and the intensity of the DLE relative peak to that of NBE increase with an increase in the VI/II flow ratio. Both effects are traced to the presence of pyramidal growth hillocks on the surface of the epilayer and to their increased density at high VI/II ratios. Monochromatic CL images show that there are two kinds of luminescent centers contributing to the NBE. The one that emits at slightly lower energies is only found, together with the DLE centers, within the growth hillocks. The one that emits at a slightly higher energy is found from surrounding areas. The concomitant appearance of DLE centers and low energy NBE centers shows that they share a common origin. Excitation intensity dependence of the photoluminescence of the NBE centers identifies as donor–acceptor-pair recombinations. © 2000 American Institute of Physics.
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78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Dz II-VI semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Hydrogen-assisted pulsed-laser deposition of (001)CeO2 on (001) Ge

D. P. Norton, J. D. Budai, and M. F. Chisholm

Appl. Phys. Lett. 76, 1677 (2000); http://dx.doi.org/10.1063/1.126133 (3 pages) | Cited 18 times

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The growth of epitaxial (001)CeO2 on a (001) Ge surface using a hydrogen-assisted pulsed-laser deposition method is reported. Hydrogen gas is introduced during film growth in order to reduce or eliminate the presence of the GeO2 from the semiconductor surface during the initial nucleation of the metal–oxide film. The hydrogen partial pressure and substrate temperature are selected to be sufficiently high such that the germanium native oxides are thermodynamically unstable. The Gibbs free energy of CeO2 is larger in magnitude than that of the Ge native oxides, making it more favorable for the metal–oxide to reside at the interface in comparison to the native Ge oxides. By satisfying these criteria, the metal–oxide/semiconductor interface is shown to be atomically abrupt with no native oxide present. © 2000 American Institute of Physics.
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81.15.Fg Pulsed laser ablation deposition
68.55.-a Thin film structure and morphology
65.20.-w Thermal properties of liquids
65.40.gd Entropy
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Step-by-step excimer laser induced crystallization of a-Si:H

P. Lengsfeld, N. H. Nickel, and W. Fuhs

Appl. Phys. Lett. 76, 1680 (2000); http://dx.doi.org/10.1063/1.126134 (3 pages) | Cited 39 times

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Amorphous silicon films (a-Si:H) with a hydrogen content of 10 at. % were crystallized employing a step-by-step crystallization method. Structural changes during the sequential crystallization process were monitored by Raman spectrometry. Initially, at low laser fluences EL, a two-layer system is created. Independent of the thickness of the a-Si:H layer explosive crystallization of a thin surface layer is observed at EL ≥ 100 mJ/cm2 confirming recent theoretical results. Crystallization is accompanied by dehydrogenation. In completely crystallized poly-Si a residual H concentration of up to 5 at. % was observed. © 2000 American Institute of Physics.
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68.55.-a Thin film structure and morphology
61.43.Dq Amorphous semiconductors, metals, and alloys
81.05.Cy Elemental semiconductors
81.05.Gc Amorphous semiconductors
78.66.Db Elemental semiconductors and insulators
78.30.Am Elemental semiconductors and insulators
78.66.Jg Amorphous semiconductors; glasses
42.62.-b Laser applications
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Fk Semiconductors
79.20.Ds Laser-beam impact phenomena
68.35.Rh Phase transitions and critical phenomena

Heteroepitaxial growth of cubic GaN on Si(001) coated with thin flat SiC by plasma-assisted molecular-beam epitaxy

D. Wang, Y. Hiroyama, M. Tamura, M. Ichikawa, and S. Yoshida

Appl. Phys. Lett. 76, 1683 (2000); http://dx.doi.org/10.1063/1.126135 (3 pages) | Cited 15 times

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High-quality cubic GaN films were grown on Si(001) coated with flat ultrathin SiC under different Ga/N flux ratios. The 2.5-nm-thick cubic SiC film proved to be an effective buffer layer for cubic GaN growth on Si(001). Under a Ga-rich condition, films with local atomically flat surfaces were obtained, and the x-ray diffraction full-width at half maximum of (002) peak was 19 min for a 0.82-μm-thick film. The reduced SiC surface roughness decreased the defect density in the GaN epilayers. Under a N-rich condition, the GaN films showed statistical roughening of the surface and a characteristic columnar structure. Under the Ga-rich condition, the columns grew up and then laterally coalesced, so that an atomically flat surface with flat areas in size from 0.05 to 0.40 μm was formed. © 2000 American Institute of Physics.
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81.05.Ea III-V semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Cubic GaN epilayers grown by molecular beam epitaxy on thin β-SiC/Si (001) substrates

D. J. As, T. Frey, D. Schikora, K. Lischka, V. Cimalla, J. Pezoldt, R. Goldhahn, S. Kaiser, and W. Gebhardt

Appl. Phys. Lett. 76, 1686 (2000); http://dx.doi.org/10.1063/1.126136 (3 pages) | Cited 9 times

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The molecular beam epitaxy of cubic GaN on Si(001) substrates, which were covered by a 4 nm thick β-SiC layer, is reported. The structural and optical properties of the cubic GaN epilayers were studied by transmission electron microscopy, high-resolution x-ray diffraction, and low-temperature photoluminescence measurements. We find clear evidence for the growth of cubic GaN layers almost free of hexagonal inclusions. The density of extended defects and the near band edge photoluminescence of the cubic GaN layers grown at substrate temperatures of 835 °C is comparable to that of high quality cubic GaN epilayers grown by molecular beam epitaxy on GaAs (001) substrates. © 2000 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
61.72.Nn Stacking faults and other planar or extended defects

Dense arrays of ordered GaAs nanostructures by selective area growth on substrates patterned by block copolymer lithography

R. R. Li, P. D. Dapkus, M. E. Thompson, W. G. Jeong, C. Harrison, P. M. Chaikin, R. A. Register, and D. H. Adamson

Appl. Phys. Lett. 76, 1689 (2000); http://dx.doi.org/10.1063/1.126137 (3 pages) | Cited 105 times

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GaAs has been selectively grown in a hexagonally ordered array of nanometer-scale holes with a density as high as ∼ 1011/cm2 by metalorganic chemical vapor deposition. This array of holes was created using block copolymer lithography, in which a thin layer of diblock copolymer was used as an etching mask to make dense holes in a 15-nm-thick SiNx film. These selectively grown nanoscale features are estimated to be 23 nm in diameter with narrow lateral size and height distributions as characterized by field-emission scanning electron microscopy and tapping mode atomic force microscopy. The narrow size distribution and uniform spatial position of the nanoscale dots we report offer potential advantages over self-assembled dots grown by the Stranski–Krastanow mode. © 2000 American Institute of Physics.
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81.05.Ea III-V semiconductors
61.46.-w Structure of nanoscale materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.07.-b Nanoscale materials and structures: fabrication and characterization
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