bluuebunny/crossref_metadata_2025_split huggingface dataset:
Non‐linear thermal broadening of exciton lines in CdTe self‐organized quantum dots
Authors: Ikeda K. , Ogawa Y. , Minami F. , Kuroda S. , Takita K. 
Published: March 2006

AbstractMicro‐photoluminescence is used to study the temperature dependence of CdTe self‐assembled quantum dots. The observation of the micro‐photoluminescence spectra with temperature shows that there are two different structures, namely the zero‐phonon line and the phonon sidebands. When the temperature increases, the sidebands become clearer and show substantial broadening. The experimental data are reproduced well by a theoretical model taking into account the carrier‐acoustic‐phonon coupling. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optically pumped ultraviolet lasing of BeMgZnSe based quantum well laser structures
Authors: Niiyama Yuuki , Murata Tomoyuki , Watanabe Masahiro 
Published: March 2006

AbstractUltraviolet lasing by optically pumping from BeMgZnSe quantum well laser structures on GaP(001) substrate was demonstrated using molecular beam epitaxy (MBE). The lasing wavelength was 373 nm at 13 K. The threshold power density at 13 K was 415 kW/cm2. In addition, the characteristic temperature from 13 to 90 K was 87 K. The lasing was confirmed up to 130 K. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
MOVPE growth and study of ZnCdSe/ZnSSe MQW structures for green VCSELs
Authors: Kuznetsov P. I. , Yakushcheva G. G. , Jitov V. A. , Zakharov L. Yu. , Shchamkhalova B. S. , Kozlovsky V. I. , Sannikov D. A. , Skasyrsky Ya. K. , Tiberi M. D. 
Published: March 2006

AbstractZnCdSe/ZnSSe MQW structures for an electron beam pumped VCSEL with resonant periodic gain were grown by MOVPE at 425–470 °C. Strong contamination of the structure by Ga from a GaAs substrate was found and its effect on the growth rate and photoluminescence characteristics was studied. A protective thin ZnSSe layer deposited at lower temperature (350 °C) or thin layers of ZnS and ZnS/ZnSSe SL grown at temperature 425–470 °C prevent Ga penetration and allowed improving the quality and periodicity of the structure. Based on the grown MQW structure, green VCSEL was fabricated. Lasing at 542 nm with 3 W output power was achieved at RT and 40 keV. The threshold was as low as 8 A/cm2. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Suppression of electron‐spin relaxation induced by magnetic fields in a Cd1–xMnxTe quantum well
Authors: Seo K. , Kayanuma K. , Aoshima I. , Nishibayashi K. , Souma I. , Murayama A. , Oka Y. 
Published: March 2006

AbstractCarrier‐spin relaxation under a magnetic field has been studied in a diluted magnetic semiconductor quantum well (DMS‐QW) of Cd0.95Mn0.05Te, by means of pump‐probe absorption spectroscopy. With resonant excitation using a circularly polarized pump‐pulse, dynamical spin‐flip processes of an electron and heavy‐hole (hh) are clearly observed in time dependences of the circularly polarized differential absorbance. In 0 T, time constants of 17 ps and 0.4 ps for the electron‐ and hh‐spin relaxations in the Cd0.95Mn0.05Te QW are shorter than those of 46 ps and 1.0 ps in a non‐magnetic CdTe QW, due to s‐d exchange interactions between the carriers and Mn spins. The spin‐flip time of the electron due to the exchange mechanism is determined as 27 ps. In an intense magnetic field of 5 T, the electron‐spin relaxation due to the exchange mechanism is found to be strongly suppressed in the DMS‐QW by magnetic‐field‐induced pinning of the Mn spins, exhibiting a longer time constant of 29 ps than that of 17 ps in 0 T. The role of LO‐phonon is also discussed in the electron‐spin relaxation under magnetic fields. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoluminescence from Cd(Se,Te) quantum dots in a ZnSe matrix
Authors: Lyublinskaya O. G. , Sedova I. V. , Sorokin S. V. , Nekrutkina O. V. , Toropov A. A. , Ivanov S. V. 
Published: March 2006

AbstractWe report on the photoluminescence (PL) and PL excitation studies of CdSe/ZnSe quantum dots (QDs) grown by molecular beam epitaxy using super‐strained CdTe fractional monolayer deposition prior to the CdSe growth. We have shown that introduction of CdTe stressor initiates the formation of a dense array of Cd(Se,Te) QDs and demonstrated the co‐existence of type‐I and type‐II structures within the dot sheet. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical properties of Cd(Zn)Se/ZnMgSSe heterostructures with fractional QD‐like CdSe insertions at high excitation levels
Authors: Lutsenko E. V. , Gurskii A. L. , Pavlovskii V. N. , Zubialevich V. Z. , Yablonskii G. P. , Sedova I. V. , Sorokin S. V. , Toropov A. A. , Ivanov S. V. , Kop'ev P. S. 
Published: March 2006

AbstractIt was found that in the Cd(Zn)Se/ZnMgSSe heterostructures with QD‐like CdSe insertions in the lasing regime the structure changes take place manifesting itself, first, in the irreversible blue shift of the laser radiation spectra. This process depends on excitation intensity and on the cavity length, correlating with the inherent radiation density in the cavity. At excitation densities above 250 kW/cm2, the reduction of the radiative efficiency was observed. The second process is the increase of radiation intensity during laser operation under certain excitation conditions caused by the self‐annealing of the laser structure induced by the inherent laser light and resulting in a decrease of the laser threshold by about 15–20%. Choosing the appropriate excitation regime, one may prolong the lifetime of this type of lasers. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Study of annealing influence on electrical and morphological properties of ZnO:Ga thin films
Authors: Khranovskyy V. , Grossner U. , Lasorenko V. , Lashkarev G. , Svensson B. G. , Yakimova R. 
Published: March 2006

AbstractIn this study, the influence of thermal annealing in different ambients on the electrical and morphological properties of Ga‐doped ZnO films with 1wt.% gallium acetylacetonate in the precursor mix is investigated systematically. As‐grown samples were prepared on c‐plane Al2O3 by PEMOCVD with a substrate temperature of 300 °C and possess a resistivity of about 10–2 Ω cm. The annealing was realized in isochronal steps between 300 to 1000 °C for 1 hour in argon and air ambient, respectively. The resistivity of the films was found to be dependent on the annealing atmosphere. During annealing in air, the resisitivity increases monotically with an abrupt reduction at 800 °C, whereas the annealing in argon does not induce significant changes but results in two clear minima at 300 °C and 800 °C. These effects are explained with crystal improvement at low temperature (300 °C) and successive dopant activation at higher temperature (800 °C). Furthermore, an anomalous surface flattening at 800°C was observed. The obtained results suggest that the annealing procedure does allow to decrease the resistivity and roughness of as‐grown ZnO:Ga films, what would be beneficial for the application of PEMOCVD‐grown ZnO thin films for the formation of abrupt junctions in p–n device structures. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
MOVPE‐grown ZnSe/ZnSSe structures for blue VCSEL with resonant periodic gain
Authors: Korostelin Y. V. , Kozlovsky V. I. , Kuznetsov P. I. , Landman A. I. , Sannikov D. A. , Tiberi M. D. 
Published: March 2006

AbstractThe long period ZnSe/ZnSxSe1–x (x = 0.2–0.4) MQW structures for the electron beam longitudinally pumped laser were grown by metalorganic vapour phase epitaxy on ZnSSe substrates with 5–13° misorientation from (001) to (111)A crystal plane. The best structures with up to 40 QWs had mirror like surface and high intense cathodoluminescence at room temperature (RT). The substrates were cut from ZnSSe single crystals obtained by seeded physical vapour transport. Based on the obtained structures, the etalons were fabricated for electron beam pumping. Lasing at 445 and 460 nm was achieved at T = 80 K and RT, respectively. Output power of the laser was about 1 W at T = 80 K and much less at RT. Possible reasons are discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spin flip Raman spectroscopy on heavily doped ZnMnSe layers
Authors: Lentze M. , Smith L. , Wolverson D. , Grabs P. , Geurts J. , Molenkamp L. 
Published: March 2006

AbstractThe influence of carrier concentration on electronic spin flip transitions in the conduction band of heavily doped diluted magnetic semiconductors is analysed experimentally by spin flip Raman spectroscopy (SFRS). Bulk‐like (Zn,Mn)Se epitaxial layers with electron concentrations between n = 1016 cm–3 and n = 1019 cm–3 are investigated. Spin flip Raman signals appear in samples with doping concentration up to 1018 cm–3, i.e., near the insulator‐to‐metal transition. Varying the doping level we observe a systematic broadening of SFRS linewidth with increasing electron concentration. Furthermore, the linewidth in backward scattering geometry is significantly higher than in forward scattering. Following theoretical predictions for doped samples, from this behaviour the values of spin diffusion coefficient Ds and spin relaxation time T2 are deduced. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fabrication and characterization of polycrystalline bulk ZnO with large grain size of ∼100 µm by the spark plasma sintering
Authors: Kougo T. , Yoshikawa A. 
Published: March 2006

AbstractWe investigated to fabricate polycrystalline ZnO bulk crystal with large grain size up to 100 µm by the spark plasma sintering (SPS) in the atmosphere of low‐vacuum of ∼1 Pa air or in atmospheric pressure air. 1 µm average‐size ZnO powder of 99.999% purity was used as the raw material for sintering. The shape of samples was disk‐like of which diameter and thickness were 20 mm and 0.5–1.0 mm, respectively. We studied how the sintering conditions, in particular the sintering temperature and the applied pressure, affect the properties of sintered ZnO crystals. No additive to enhance the sintering process was used in this work. It was found that the SPS was very effective to enhance the sintering itself resulting in the grain size ranging from a few µm to ∼100 µm. Further the electrical properties of the sintered ZnO crystals were found to be very sensitive to the sintering conditions, i.e., their resistivity varied in the range from 0.02 Ω cm to ∼1000 kΩ cm depending on the grain size. The resistivity saturated in the order of 0.01 Ω cm when the grain size was above about 20 µm. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Study on electrical properties of II‐VI‐based distributed Bragg reflectors
Authors: Otte Kai , Kruse Carsten , Dennemarck Jens , Hommel Detlef 
Published: March 2006

AbstractThe key technology for electrically pumped vertical‐cavity surface‐emitting lasers (VCSEL) is the realisation of high reflectivity Bragg Mirrors (DBRs) with sufficient conductivity in vertical direction. Several nand p‐doped DBRs, consisting of ZnSSe as high index and a MgS/Zn(Cd)Se superlattice (SL) as low index material were grown on GaAs substrates. Mesa structures were prepared and furnished with metal contacts. On the one hand a sufficient conductivity of n‐doped DBRs has been achieved. The conductivity depends strongly on the period and composition of the MgS/Zn(Cd)Se‐SL. On the other hand the p‐doped DBRs showed a resistance of several orders of magnitude higher and are unlikely to be used in VCSELs. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterisation of Cd1–x–yZnxBeySe crystals by spectroscopic ellipsometry and luminescence
Authors: Wronkowska A. A. , Firszt F. , Arwin H. , Wronkowski A. , Wakuła M. , Strzałkowski K. , Paszkowicz W. 
Published: March 2006

AbstractOptical and luminescence properties of Cd1–x–yZnxBeySe solid solutions grown in the composition range 0 < x < 0.15 and 0 < y < 0.30 by the high pressure Bridgman method are reported. Spectroscopic ellipsometry was employed for determination of spectral dependence of the complex dielectric function ε(E), refractive index n(E) and absorption coefficient α(E) in the photon energy range 0.75–6.0 eV. The dispersion of the refractive index of the alloys was modelled using a Sellmeier‐type relation. The excitonic band‐gap energies were estimated from the ellipsometric and photoluminescence measurements. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Defect formation in CdTe during laser‐induced doping and application to the manufacturing nuclear radiation detectors
Authors: Gnatyuk V. A. , Aoki T. , Hatanaka Y. , Vlasenko O. I. 
Published: March 2006

AbstractThe peculiarities of electrical properties of In/CdTe/Au diodes, fabricated by the laser‐induced doping procedure, have been studied. The measurements of time dependences of reverse biased current of a great number of different samples revealed three types of the leakage current density variations with time. These variations were attributed to proper CdTe defects as well as point and extended defects generated in the act of laser‐induced doping of CdTe wafers and following fabrication of pixel detectors. The optimal conditions of laser‐induced In‐doping of CdTe wafers and formation of electrodes were elaborated. The fabricated detectors had sharp I‐V characteristics with a low leakage current, possessed a high energy resolution at room temperature and showed promise for nuclear radiation imaging devices. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Far infrared selective absorption in uniformly iodine doped MBE CdTe/CdMgTe quantum wells – with no energetic scaling
Authors: Szot M. , Karpierz K. , Maude D. K. , Sadowski M. L. , Kossut J. , Grynberg M. 
Published: March 2006

AbstractMagnetophotoconductivity spectra of uniformly doped CdTe/Cd0.8Mg0.2Te quantum wells are presented. They were taken for fixed photon energy causing the transitions between the shallow donor levels splitted by an external magnetic field. They exhibit a surprising lack of sensitivity on the photon energy – for the energy range 2.2–13 meV the peaks in the spectra are recorded at the same magnetic field. The results are understood by taking into account the existence of local potential fluctuations in the structure which do cause localization of conducting electrons. The absorption can always occur on donors located in different regions and it leads to the mentioned lack of energetic scaling. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrical manifestation of ferromagnetic ordering in phosphorus‐doped semimagnetic semiconductor Zn1–xMnxTe
Authors: Van Khoi Le , Gałązka R. R. 
Published: March 2006

AbstractZn1–x Mnx Te semimagnetic semiconductor doped with phosphorus has been investigated by means of the resistivity, Hall effect, andmagnetic susceptibilitymeasurements. Itwas demonstratedthat in Zn1–x Mnx Te:P the Mn‐Mn antiferromagetic superexchange interaction can be controlled by changing the hole concentration and that the Mn‐Mn ferromagnetic interaction was observed at the hole concentration level of 5 × 1018 cm–3. This Mn‐Mn ferromagnetic interaction has resulted in a strong temperature dependence of the resistivity, which follows log ρ ∼ 1/T 2. A phenomenological calculation has been performed taking into account the magnetic contribution to the carrier binding energy. The calculation well describes the temperature dependence of the resistivity of the highly P‐doped Zn1–x Mnx Te crystals. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical properties of CdSe/ZnSe nanostructures grown by MBE on virtual Si/Ge substrates
Authors: Onishchenko Evgeny E. , Kazakov Igor P. , Rzaev Murvetali M. 
Published: March 2006

AbstractIn this paper, the luminescent properties (5–300 K) of CdSe/ZnSe quantum dot structures grown on conventionally used GaAs(100) substrates and Si(100)/Ge virtual substrates are studied. It has been established that the quantum dot structures grown on different substrates exhibit comparable high luminescence efficiency. Two peaks were observed in the luminescence spectra of some samples grown on GaAs as well as Si/Ge substrates. They are attributed to the emission from two types CdSe islands (quantum dots) between which there is no efficient exciton transfer. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The effects of in situ annealing on CdSe quantum dots grown by ALE
Authors: Morrod J. K. , Graham T. C. M. , Warburton R. J. , Prior K. A. 
Published: March 2006

AbstractThe effect of increasing annealing times on the emission energies and dot densities of ZnSe/CdSe quantum dots has been studied. Ensemble PL carried out at 77 K demonstrates the energy shift of the main peak attributed to fractional monolayer islands, which is due to annealing. µPL conducted at 4 K was then used to study the increased spectral separation of the emission energies from SK dots. Finally, ex‐situ AFM measurements of two samples, showed a reduction in the Stranski‐Krastanow dot density of approximately one order of magnitude due to annealing. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Manipulation of exciton spin states in a dilute magnetic semiconductor by nanostructured ferromagnets
Authors: Halm S. , Seifert F. , Kümmell T. , Bacher G. , Schuster E. , Keune W. , Puls J. , Henneberger F. 
Published: March 2006

AbstractA hybrid of nanostructured Fe/Tb multilayer ferromagnets and ZnCdMnSe dilute magnetic semiconductor (DMS) quantum well was studied by magneto‐micro‐photoluminescence (µPL) spectroscopy. When the sample is magnetized in an external magnetic field an additional fringe field from the nanomagnets effectively modulates the local exciton spin states in the quantum well (QW) due to the giant Zeeman effect. Observation of 1.5% of remanent PL polarization degree from the QW gives a direct proof of remanent exciton spin polarization in the DMS. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Internal laser parameters and optical properties of laser with CdSe quantum dots in ZnSe matrix
Authors: Lutsenko E. V. , Gurskii A. L. , Pavlovskii V. N. , Zubialevich V. Z. , Yablonskii G. P. , Sedova I. V. , Sorokin S. V. , Toropov A. A. , Ivanov S. V. , Kop'ev P. S. 
Published: March 2006

AbstractPhotoluminescence (PL), PL excitation (PLE) spectra as well as internal laser characteristics of CdSe quantum dots (QDs) in ZnSe matrix grown by molecular beam epitaxy (MBE) and multi‐cycle migration enhanced epitaxy (MEE) were investigated. The peak PL intensity of the CdSe QDs grown by MEE in an asymmetric waveguide is by one order of magnitude more than that of the CdSe QDs grown by MBE in a symmetric waveguide. As a result, the laser characteristics have been significantly improved. The internal laser parameters were estimated to be: ΓG0 ∼ 66 cm–1, ηi ∼ 13–17%, αi ∼ 5–15 cm–1 for MBE CdSe QDs and ΓG0 ∼ 69 cm–1, ηi ∼ 42%, αi ∼ 2–10 cm–1 for MEE CdSe QDs. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth and optical property characterizations of ZnTe:(Al,N) layers using two co‐doping techniques
Authors: Ichiba A. , Ueno J. , Ogura K. , Katsuta S. , Kobayashi M. 
Published: March 2006

AbstractIn order to get around the high and activated n‐doping levels for ZnTe, the co‐doping technique known as effective method to overcome the dopant compensation was explored. The co‐doping concept is to introduce two oppositely polar atoms at the same time in a 2:1 ratio, forming metastable three‐atom complexes located at adjacent crystal sites. In this study, two types of deposition process were considered to place the co‐dopants at the intended site, and the co‐doped ZnTe:(Al, N) layers were grown on (001) oriented ZnTe substrates by molecular beam epitaxy. From the low temperature PL spectra, the increase of Al activation was confirmed by using co‐doping sequences, and the activation of N dopant was also confirmed for one doping sequence even thought the doping level was maintained the same. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Formation of CdO dots on atomically flat ZnO surfaces
Authors: Ebihara M. , Suemune I. , Kumano H. , Nakashita T. , Machida H. 
Published: March 2006

AbstractAtomically flat terraced ZnO surfaces were prepared with thermal annealing in air. CdO dots were successfully formed on the ZnO substrate surfaces with in‐situ post‐growth thermal annealing of CdO layers grown by metalorganic molecular‐beam epitaxy. Well‐organized alignment of the CdO dots along surface atomic‐step edges on the terraced surfaces is demonstrated. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Morphology of CdSe/ZnSe quantum dots grown by MBE
Authors: Bougerol C. , André R. , Robin I. C. , Gilles B. , van Daele B. , van Tendeloo G. 
Published: March 2006

AbstractThe features of CdSe/ZnSe quantum dots (QDs) grown by molecular beam epitaxy at 280 °C and 240 °C are studied by transmission electron microscopy (TEM), atomic force microscopy (AFM) and photoluminescence (PL). The epitaxial structures consist of a single layer of CdSe islands sandwiched between two 40 nm thick ZnSe layers grown on a [100]‐oriented GaAs substrate. UHV‐AFM shows that islands are formed as a result of strain relaxation in 3 ML of CdSe pseudomorphically deposited on ZnSe. After encapsulation at 240 °C, there is no change in the QDs' morphology. On the other hand, at higher temperature, interdiffusion and segregation phenomena take place. Flat islands originating from a wetting layer and pointing to the substrate are observed, with a Cd concentration much lower in their center than at the outskirts. Both size and composition are consistent with the ∼2.35 eV PL energy that we measured. Moreover the unexpected QD morphology with Cd‐rich outskirts can explain why the PL decay time depends on the samples because the confinement of holes in the QD edges makes the electron‐hole overlap very sensitive to QD size. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Anisotropic magnetic properties of Zn1–xCoxO thin films grown by pulsed laser deposition
Authors: Lee J. W. , Kuroda S. , Yamada S. , Takita K. 
Published: March 2006

AbstractThe anisotropic magnetic and magneto‐transport properties of Zn1–x Cox O thin films were investigated. By pulsed laser deposition (PLD) technique, the (0001) plane (c ‐plane) or (11‐20) plane (a ‐plane) Zn1–x Cox O layer was deposited on the c ‐surface or r ‐surface sapphire substrate, respectively, and magnetization and magnetoresistance (MR) measurements were performed with magnetic fields parallel or perpendicular to the film plane. It was found that the magnitudes of the magnetization and MR were larger when magnetic fields were applied along a ‐ or b ‐axis than those under magnetic fields along c ‐axis, irrespective of the growth orientation of the films. The consistency of the anisotropy between magnetization and MR is considered to originate from the anisotropic electronic state of Co d ‐electrons. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
ZnO crystals for substrates in micro and optoelectronic applications
Authors: Grasza K. , Mycielski A. , Domagała J. , Domukhovski V. , Paszkowicz W. , Sakowska H. , Hofman W. 
Published: March 2006

AbstractZinc oxide crystals were grown by Chemical Vapour Transport using Contactless Crystal Growth technique. To apply powdered source material and long ampoules, modified temperature field was applied. 2.5 cm diameter crystals were obtained. The largest grains yielded 0.5 cm2 single crystalline substrates. The FWHM of the rocking curve was usually exceeding 60 arcsec, but areas with FWHM as low as 29 arcsec were also found. The electrical p‐type conductivity of As‐doped crystal was identified as increased arsenic content grain surface effect. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)