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1 Nov 2001

Volume 90, Issue 9, pp. 4307-4883

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Temperature dependence of the lasing wavelength of InGaAs quantum dot lasers

J. D. Thomson, H. D. Summers, P. M. Smowton, E. Herrmann, P. Blood, and M. Hopkinson

J. Appl. Phys. 90, 4859 (2001); http://dx.doi.org/10.1063/1.1402666 (3 pages) | Cited 4 times

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We observe that the emission wavelength of edge-emitting InGaAs quantum dot lasers has a much weaker temperature dependence (0.6 Å K−1) than equivalent quantum well devices (3 Å K−1). Measured gain and absorption spectra show that the gain peak wavelength due to dot states is almost independent of temperature for a given value of peak gain whereas the absorption edge shifts at a rate of about 2 Å K−1. Above 100 K the occupancy of dot states can be described by Fermi functions and on this basis we find that the measured gain and absorption spectra are in excellent quantitative agreement. Although the band edge energy reduces with increasing temperature, this analysis shows that the energy distribution of dot states matches the evolution of the Fermi functions such as to leave the quasi Fermi level separation and the wavelength of the gain peak unchanged as a function of temperature for a given value of peak gain. This energy distribution is a consequence of the dot size distribution so the match to the Fermi functions is probably fortuitous. © 2001 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.21.La Quantum dots
78.67.Hc Quantum dots

Submicron nickel deposition on silicon from an electrolytic solution controlled by near-field optics

H. Diesinger, A. Bsiesy, and R. Hérino

J. Appl. Phys. 90, 4862 (2001); http://dx.doi.org/10.1063/1.1405136 (3 pages) | Cited 7 times

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The application of a near-field optical device to the electrochemical deposition of submicron nickel dots on silicon is demonstrated. The silicon–electrolyte junction behaves like a Schottky diode where the electrolyte plays the role of the metal. The junction is reverse biased so that only a negligible dark current is flowing across the junction. The optical tip of the near-field device is used as a local lightsource to control a photocurrent on a submicron scale, which allows one to create submicron objects of nickel by locally triggering the electrochemical reduction of nickel ions. The effect of the lateral diffusion of the photogenerated carriers on the form of the deposited nickel dots is described by a two-dimensional carrier diffusion model. © 2001 American Institute of Physics.
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81.15.Pq Electrodeposition, electroplating
81.05.Bx Metals, semimetals, and alloys
81.05.Cy Elemental semiconductors
82.45.Qr Electrodeposition and electrodissolution
72.40.+w Photoconduction and photovoltaic effects
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
81.16.Be Chemical synthesis methods
73.40.Mr Semiconductor-electrolyte contacts

Yellow-to-violet upconversion in neodymium oxide nanocrystal/titania/ormosil composite sol–gel thin films derived at low temperature

Wenxiu Que, C. H. Kam, Y. Zhou, Y. L. Lam, and Y. C. Chan

J. Appl. Phys. 90, 4865 (2001); http://dx.doi.org/10.1063/1.1408262 (3 pages) | Cited 18 times

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Neodymium (III) oxide nanocrystals synthesized by the inverse microemulsion technique were dispersed in sol–gel titania/organically modified silane (ormosil) composite thin films for photonic applications. X-ray diffraction analysis and transmission electron microscopy observation show that the neodymium oxide nanoparticles have a nanocrystalline structure and that the size of the nanoparticles is in the range of 5–60 nm. An intense room-temperature yellow-to-violet upconversion emission at 402 nm (4D3/2→4I13/2) was measured from the composite thin film heated at 100 °C upon excitation with a yellow light at 587 nm. In addition to this violet emission, ultraviolet emission at 372 nm and blue emission at 468 nm were also observed. The lifetime of the violet emission was measured and the mechanism of the upconversion emission is proposed, and they indicate excited-state absorption originating from the long-lived 4F3/2 excited state should be responsible for the yellow-to-violet upconversion. © 2001 American Institute of Physics.
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42.70.Hj Laser materials
81.07.Bc Nanocrystalline materials
78.55.-m Photoluminescence, properties and materials
78.66.Sq Composite materials
61.46.-w Structure of nanoscale materials
68.55.-a Thin film structure and morphology
81.10.Dn Growth from solutions
81.10.Fq Growth from melts; zone melting and refining
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Inhomogeneous incorporation of In and Al in molecular beam epitaxial AlInGaN films

A. Cremades, V. Navarro, J. Piqueras, A. P. Lima, O. Ambacher, and M. Stutzmann

J. Appl. Phys. 90, 4868 (2001); http://dx.doi.org/10.1063/1.1407849 (3 pages) | Cited 8 times

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Plasma-induced molecular beam epitaxial AlInGaN heterostructures have been characterized by spatial resolved cathodoluminescence and x-ray energy dispersive microanalysis. Competitive incorporation of Al and In has been observed, with the formation of In-rich regions, showing enhanced luminescence around surface pinholes. These island-like In-rich regions are favored by growth at lower temperature due to the higher incorporation of indium into the alloy. The elastic strain relaxation associated to pinhole formation induces preferential local indium incorporation. The diffusion of carriers to these areas with reduced band gap enhances the luminescence emission of the quaternary film. The width and intensity of the luminescence appear to be sensitive to the mismatch between the quaternary film and the GaN layer below. © 2001 American Institute of Physics.
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78.60.Hk Cathodoluminescence, ionoluminescence
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
81.40.Jj Elasticity and anelasticity, stress-strain relations
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.66.Fd III-V semiconductors

Stopping cross sections for 0.3–2.5 MeV protons in GaN and InP

T. Ahlgren and E. Rauhala

J. Appl. Phys. 90, 4871 (2001); http://dx.doi.org/10.1063/1.1337076 (3 pages) | Cited 2 times

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The stopping cross sections of the III–V semiconductor materials GaN and InP for 0.3–2.5 MeV 1H have been studied by the Rutherford backscattering technique. The data are given with an estimated uncertainty better than 2% and the agreement with earlier data existing for InP below 500 keV is good. A commonly used model ZBL-85 predicts the data correctly at the high energy end of our energy interval, but overestimates the stopping values by 7% and 4% for GaN and InP, respectively, at the lower energies. © 2001 American Institute of Physics.
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61.85.+p Channeling phenomena (blocking, energy loss, etc.)
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.05.Ea III-V semiconductors

Enhancement of magnetoresistance in the intermediate state of Pr0.5Sr0.3Ca0.2MnO3

C. W. Chang and J. G. Lin

J. Appl. Phys. 90, 4874 (2001); http://dx.doi.org/10.1063/1.1408263 (3 pages) | Cited 4 times

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Current–voltage (I–V) characteristics of Pr0.5Sr0.3Ca0.2MnO3 are measured at different temperatures and different fields. Our data of I–V curves show a crossover from linear to nonlinear behavior at the temperature lower than the charge ordering temperature. New findings in this work include (i) abrupt jumps/drops of voltage in each I–V curve below 100 K and (ii) an enhancement of magnetoresistance (MR) ratio from 15% to 20% which is associated with the unusual voltage jumps/drops in I–V curves. The enhancement of MR ratio evidences the existence of an intermediate state between the charge ordering state and the charge ordering breakdown state. Most importantly, the existence of such intermediate state provides a new route to achieve a low field colossal magnetoresistance for future applications of spintronics. © 2001 American Institute of Physics.
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75.50.Dd Nonmetallic ferromagnetic materials
75.47.Gk Colossal magnetoresistance
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
71.45.-d Collective effects

Crystalline orientation effects on the electronic transport properties of LaMnOy thin films

J. H. Zhang, N. B. Ming, and X. G. Li

J. Appl. Phys. 90, 4877 (2001); http://dx.doi.org/10.1063/1.1402665 (3 pages)

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We have grown epitaxial and polycrystalline LaMnOy thin films on a LaAlO3 substrate by the off-axis magnetron sputtering technique and investigated the crystalline orientation effects on the electronic transport properties. Lattice mismatch, crystalline quality, resistivity, resistivity transition temperature Tp, and magnetoresistance (MR) in epitaxial films exhibit crystalline orientation dependence. The largest Tp and MR are observed in the (111) oriented films. In the polycrystalline films, the Tp is smaller than that of the (011)/(111) oriented films but higher than that of the (001) oriented films. The MR increases with decreasing temperature in contrast to that of the epitaxial films in which the MR experiences a peak near Tp. Oxygen annealing decreases MR and resistivity, and increases Tp in the order: (111)<(011)<(001)<(polycrystalline). The above results suggest that the structure and composition of the epitaxial films improve in the order: (001)<(011)<(111). © 2001 American Institute of Physics.
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73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.61.-r Electrical properties of specific thin films
81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology
68.55.Nq Composition and phase identification
72.60.+g Mixed conductivity and conductivity transitions
FREE

Comment on: “Energy band structures of the low-dimensional antiferromagnets Sr2CuO3 and Sr2CuO2Cl2” [J. Appl. Phys. 87, 4897 (2001)]

H. Rosner, D. M. Johannes, and S.-L. Drechsler

J. Appl. Phys. 90, 4880 (2001); http://dx.doi.org/10.1063/1.1407847 (2 pages) | Cited 1 time

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Recent electronic structure calculations for the title compounds performed by Wu et al. [H. Wu et al., J. Appl. Phys. 87, 4897 (2000)] are critically reconsidered by applying highly accurate full-potential band structure methods. It is shown that due to a nonconverged basis set the band structure calculations presented here by the authors disagree considerably with those of Wu et al. © 2001 American Institute of Physics.
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71.20.Ps Other inorganic compounds
75.50.Ee Antiferromagnetics
75.10.Lp Band and itinerant models
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Response to “Comment on ‘Energy band structures of the low-dimensional antiferromagnets Sr2CuO3 and Sr2CuO2Cl2’ ” [J. Appl. Phys. 90, 3708 (2001)]

Hua Wu and Qing-qi Zheng

J. Appl. Phys. 90, 4882 (2001); http://dx.doi.org/10.1063/1.1407848 (2 pages)

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An improvement is made on our previous band results of Sr2CuO3 and Sr2CuO2Cl2 by including the extended Sr 4p valence orbital in the present self-consistent calculations. The differences between our improved results and those of others are mainly due to different evaluation of the ionicity in these compounds. © 2001 American Institute of Physics.
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71.20.Ps Other inorganic compounds
75.10.Lp Band and itinerant models
75.50.Ee Antiferromagnetics
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
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