bluuebunny/crossref_metadata_2025_split huggingface dataset:
Correlation between the leakage current and the thickness of GaN‐layer of AlGaN/GaN‐HFET
Authors: Hinoki Akihiro , Kamiya Shinichi , Tsuchiya Tadayoshi , Yamada Tomoyuki , Kikawa Junjiroh , Araki Tsutomu , Suzuki Akira , Nanishi Yasushi 
Published: June 2007

AbstractFor further improvements in AlGaN/GaN heterojunction field‐effect transistor performance, it is necessary to reduce the buffer leakage current of the GaN layer. We studied the correlation between the buffer leakage current and the thickness of GaN layers. Unintentionally doped GaN layers with different thicknesses from 0.2 μm to 2 μm were grown by metal organic chemical vapor deposition on SiC substrates. The buffer leakage current of the GaN layer was measured after deposition of ohmic metal contact and the dislocations were observed using a transmission electron microscopy. The thinner samples had a smaller buffer leakage current although a higher density of threading dislocations. We discussed the origin for the reduction in the buffer leakage current for the thinner GaN layers by assuming that the residual carrier in the GaN layer was compensated by dislocations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Self‐separation of thick two inch GaN layers grown by HVPE on sapphire using epitaxial lateral overgrowth with masks containing tungsten
Authors: Hennig Ch. , Richter E. , Weyers M. , Tränkle G. 
Published: June 2007

AbstractSelf‐separation of freestanding GaN layers of 50 mm diameter and thicknesses from around 50 µm to several hundred mm has been achieved using lateral overgrowth over silicon nitride masks with a high fraction of tungsten (WSiN). The moment of the separation was found to change with both the area ratio of the mask and the absolute structure size.
Reduction of threading dislocations in nonpolar 4H‐AlN on 4H‐SiC (11$ \bar 2 $0) grown by molecular‐beam epitaxy with slightly Al‐rich conditions
Authors: Horita M. , Suda J. , Kimoto T. 
Published: June 2007

AbstractGrowth of AlN on (11$ \bar 2 $0) 4H‐SiC a‐plane face substrates by molecular‐beam epitaxy has been investigated. Nonpolar (11$ \bar 2 $0) 4H‐AlN was isopolytypically grown on (11$ \bar 2 $0) 4H‐SiC substrates under slightly Al‐rich conditions. When growth was performed under slightly N‐rich conditions, (11$ \bar 2 $0) 2H‐AlN with high stacking fault density was obtained. A reduced density of defects such as stacking faults and threading dislocations was achieved by growing in slightly Al‐rich conditions. For the best sample, the stacking fault density was 2 × 105 cm–1, and the partial and perfect threading dislocation densities were 7 × 107 cm–2 and 1 × 107 cm–2, respectively.
Void assisted dislocation reduction in AlN and AlGaN by high temperature MOVPE
Authors: Balakrishnan K. , Iida K. , Bandoh A. , Iwaya M. , Kamiyama S. , Amano H. , Akasaki I. 
Published: June 2007

AbstractBridge layers of AlN and Al0.25Ga0.75N have been formed on linearly grooved substrates of 6H‐SiC by high temperature metal organic vapor phase epitaxy. Void assisted dislocation reduction was achieved in the formed bridge layers. Distinct difference in growth and coalescence behaviors of the Al0.25Ga0.75N layers was observed when the layers were grown on the substrates with grooves formed along 〈1$ \bar 1 $00〉 and 〈11$ \bar 2 $0〉 directions. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimization of HVPE growth of freestanding c‐plane GaN layers using (100) γ‐LiAlO2 substrates
Authors: Richter E. , Hennig Ch. , Wang L. , Zeimer U. , Weyers M. , Tränkle G. 
Published: June 2007

AbstractFreestanding c‐plane GaN substrates are obtained using (100) γ‐LiAlO2 substrates due to spontaneous separation during post‐growth cool down. It is shown that by growth optimization the structural properties of 200 µm thick freestanding GaN layers can be improved resulting in FWHM values of ω‐rocking curves below 400 arcsec for 002 and 302 reflection and threading‐dislocation densities below 109 cm–2. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
InN clusters in InxGa1–xN quantum wells: analysis of bond lengths
Authors: Lei H. , Jiang X. J. , Chen J. , Belabbas I. , Ruterana P. , Nouet G. 
Published: June 2007

AbstractIn InxGa1–xN quantum wells, In‐N and Ga‐N bond lengths were analysed with a Stillinger‐Weber potential optimized for the III‐V nitride semiconductors. The Ga‐N and In‐N average bond lengths show a compressed state depending on the In concentration of the cluster.
Novel field plate structure of AlGaN/GaN HEMTs
Authors: Nakajima Akira , Shimizu Mitsuaki , Okumura Hajime 
Published: June 2007

AbstractA novel FP structure, namely the floating field plate (FFP), is proposed to obtain a high breakdown voltage (VB) in AlGaN/GaN HEMTs. The FFP is characterized by electrically floating metals that are placed between the gate and drain electrodes beside a conventional field plate (FP). An optimization procedure for the FFP structure using an analytical model was investigated. Our numerical simulations yielded a VB value for the optimized FFP‐HEMTs of more than 2 kV, which is twice that of a conventional FP‐HEMT. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth of hexagonal GaN films on the nitridated β‐Ga2O3 substrates using RF‐MBE
Authors: Ohira S. , Suzuki N. , Minami H. , Takahashi K. , Araki T. , Nanishi Y. 
Published: June 2007

AbstractThe growth of hexagonal GaN (h‐GaN) films on the nitridated β‐Ga2O3 substrates using radio‐frequency. molecular beam epitaxy (RF‐MBE) was investigated. The β‐Ga2O3 single crystal prepared by optical floating zone method was used to a substrate for GaN film growth, and nitridated by exposing to electron cyclotron resonance nitrogen plasma. It was found that h‐GaN layer is formed on the surface of β‐Ga2O3 substrates by controlling the nitridation condition, and homo‐epitaxial growth of h‐GaN films was succesfully achieved by optimizing the RF‐MBE growth condition. The observation of cross‐sectional high‐resolution transmission electron microscopy indicated that obtained GaN films grown on these nitridated β‐Ga2O3 substrates were of a high structural quality. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The surface diffusion of Ga species on an AlGaN facet structure in low pressure MOVPE
Authors: Narita Tetuso , Honda Yoshio , Yamaguchi Masahito , Sawaki Nobuhiko 
Published: June 2007

AbstractThe diffusion of Ga species in gas phase as well as on the surface are studied in selective area growth of AlGaN in low pressure metalorganic vapor phase epitaxy. The experiments were performed on a trapezoidal stripe with (0001) facet on the top and (1‐101) facet on the sides. It was found that the ridge growth on the facets were sensitive to the growth pressure, in agreement with numerical results. At a low pressure of 100 Torr, we got a uniform thickness of AlGaN alloy, but the alloy composition was not uniform. Exponential variation of the composition gave the effective diffusion length of Ga on the order of 0.7 μm which was independent of the growth pressure. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fabrication and characterization of transparent conductive Sn‐doped β‐Ga2O3 single crystal
Authors: Suzuki N. , Ohira S. , Tanaka M. , Sugawara T. , Nakajima K. , Shishido T. 
Published: June 2007

AbstractTransparent conductive Sn‐doped β‐Ga2O3 single crystal with high crystallinity was successfully fabricated as a substrate for the growth of GaN‐based compounds. Sn‐doped β‐Ga2O3 single crystals were grown using a floating zone (FZ) method, and the properties of electrical conductivity, optical transmittance, and crystallinity were characterized to optimize the growth condition. It was found that these properties are controlled by the Sn doping concentration, and the specimen for 32 ppm Sn‐doped β‐Ga2O3 single crystal was optimized to satisfy these properties simultaneously, i.e. the substrate with the internal optical transmittance of above ∼85% in the visible region, the electrical resistivity of 4.27×10–2 Ωcm, the carrier density of 2.26×1018 cm–3, and the FWHM of X‐ray rocking curve of 43 arcsec was obtained. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Adduct formation of CP2Mg with NH3 in MOVPE growth of Mg‐doped InN
Authors: Nagai Y. , Niwa H. , Hashimoto A. , Yamamoto A. 
Published: June 2007

AbstractThe Mg doping for MOVPE InN has been studied using biscyclopentadienyllmagnesium CP2Mg as a Mg source. The InN samples grown near the upstream end of the 18 cm long susceptor have very small grain size and contain a high level of C and H contamination. The XPS analysis of the deposits obtained by the supply of CP2Mg together with NH3 reveals that new Mg compounds are formed near the upstream end of the susceptor. The new compounds are adducts of CP2Mg and NH3, because they can not be formed when only CP2Mg is supplied. The adduct formation seems to be a cause for the very small grain size and the high levels of C and H contamination. The adduct formation is suppressed at positions with a distance more than 9 cm from the upstream end. This means that designs of reactor and susceptor are very important for successful Mg doping of InN with CP2Mg. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Two‐step growth of InGaN quantum dots and application to light emitters
Authors: Yamaguchi T. , Dennemarck J. , Tessarek C. , Sebald K. , Gangopadhyay S. , Falta J. , Gutowski J. , Figge S. , Hommel D. 
Published: June 2007

AbstractA two‐step growth method for creating InGaN quantum dots (QDs) was developed by using a combination of an InxGa1–xN nucleation layer (NL) without island structures and an InyGa1–yN formation layer (FL) with an indium content lower than that of the InxGa1–xN NL. The realization of QDs was confirmed by micro‐photoluminescence (μ‐PL) measurements only for the sample with both the InxGa1–xN NL and the InyGa1–yN FL. The spectral position of the QD ensemble recombination was controlled mainly by the deposition time of the InxGa1–xN NL. Green (∼520 nm) and amber (∼600 nm) LEDs with the QD layers grown by the two‐step growth method as the active region were also fabricated and compared with that having InGaN QW layers, reported previously. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth of bulk aluminum nitride crystals
Authors: Helava H. , Davis S. J. , Huminic G. D. , Ramm M. G. , Avdeev O. V. , Barash I. S. , Chemekova T. Yu. , Mokhov E. N. , Nagalyuk S. S. , Roenkov A. D. , Segal A. S. , Vodakov Yu. A. , Makarov Yu. N. 
Published: June 2007

AbstractWe discuss the main growth issues for bulk AlN crystals: 1. durability of the crucible; 2. purity of the source; and 3. availability of large seeds. In situ‐prepared TaC crucibles and re‐crystallized powder sources are used in combination with SiC starting seeds to obtain high‐quality AlN bulk single crystals. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of non‐stoichiometry and compensation on fundamental parameters of heavily‐doped InN
Authors: Shubina T. V. , Glazov M. M. , Ivanov S. V. , Vasson A. , Leymarie J. , Monemar B. , Araki T. , Naoi H. , Nanishi Y. 
Published: June 2007

AbstractThe empirical nearest‐neighbor tight binding theory and the Harrison bond‐orbital model are exploited to investigate the variation in effective band gap, electron effective masses and dielectric constants induced by non‐stoichiometry. A model is proposed to describe absorption edges in heavily‐doped InN using the Efros‐Shklovslii approach for compensated semiconductors and taking into account the non‐parabolicity of the InN band structure. Reasonable agreement with experimental trends has been demonstrated. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoluminescence excitation spectroscopy of Er3+ ions in cubic GaN:Er
Authors: Glukhanyuk V. , Przybylińska H. , Kozanecki A. 
Published: June 2007

AbstractIn this paper we report the results of study of cubic GaN implanted with erbium by means of photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopy. Only one optical emission center is observable at resonant excitation of Er3+ ions to 4I9/2 state. The positions of erbium energy levels were determined from the results of PL and PLE measurements for 4I15/2 and 4I9/2 state. Symmetry of energy levels has been assign according to group theory. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evaluation of AlGaN/GaN‐HFET with HfAlO gate insulator
Authors: Sazawa H. , Hirata K. , Kosaki M. , Shibata N. , Furuta K. , Yagi S. , Tanaka Y. , Kinoshita A. , Shimizu M. , Okumura H. 
Published: June 2007

AbstractMetal‐insulator‐semiconductor (MIS) heterostructure field‐effect transistors (HFETs) fabricated with HfAlO as a gate insulator with high dielectric permittivity are demonstrated to achieve true enhancement‐mode operation with no gate leakage and high drain current density. Insertion of the HfAlO layer allows for forward gate bias voltages of up to +8 V without gate leakage (maximum gate current density of 1.2×10–5 mA/mm at +8 V gate bias) under direct current operation. Utilizing the extended forward gate bias swing, a maximum drain current density of 767 mA/mm is achieved, substantially higher than that of the non‐insulated HFET (427 mA/mm). A recessed‐gate MIS‐HFET with the HfAlO gate insulator exhibits a threshold voltage of +2.0 V and zero transconductance below a gate bias of +0.9 V, demonstrating true enhancement‐mode operation for the first time in recessed‐gate AlGaN/GaN‐HFETs with a maximum drain current density of 253 mA/mm at +5 V (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of substrate surface on GaN dot structure grown on Si(111) by droplet epitaxy
Authors: Otsubo Hiroaki , Kondo Toshiyuki , Yamamoto Yo , Maruyama Takahiro , Naritsuka Shigeya 
Published: June 2007

AbstractThe effect of substrate surface on GaN dot structure grown on Si(111) by droplet epitaxy using an rf plasma molecular beam epitaxy (MBE) system is reported. Compared with nitridated substrates, both enhancement of Ga migration and poorer wettability were observed on oxidized substrates, inducing enlargement of Ga droplets during nitridation. We demonstrated that the size and density of GaN dots grown by droplet epitaxy are strongly affected by pre‐treatment of the substrate. In the fabrication of GaN dots by droplet epitaxy, the importance of optimizing nitridation conditions according to the substrate surface is demonstrated. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nitride‐organic semiconductor hybrid heterostructures for optoelectronic devices
Authors: Kim Hyunjin , Dang Cuong , Song Yoon‐Kyu , Zhang Qiang , Patterson William , Nurmikko A.V. , Kim K.‐K. , Song S.‐Y. , Han Jung 
Published: June 2007

AbstractWe explore hybrid gallium nitride‐organic semiconductors as composite layered thin film materials and report on initial results of fundamental studies of carrier transport across a junction composed of InGaN and selected organic thin films, with the eventual application goal towards versatile optoelectronic devices. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multi‐color light emitting diode using polarization‐induced tunnel junctions
Authors: Grundmann Michael J. , Mishra Umesh K. 
Published: June 2007

AbstractA multi‐color light emitting diode (LED) using two distinct active regions connected via a tunnel junction was grown by rf‐plasma‐assisted molecular beam epitaxy. The LED is contacted through n‐type layers, one of which provides efficient contact to a p‐type layer via a second tunnel junction. The tunnel junctions used in the structure use the high polarization fields found in the III‐nitrides material system to narrow the depletion width of the junction. Two peaks at 405 nm and 490 nm are observed in the electroluminescence spectrum of the LED, and current‐voltage characteristics indicate a turn‐on voltage of roughly 7.5 V and dynamic series resistance of 19 Ω at 80 mA for a 300 μm square device. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of the elemental composition of trace analytes in complex matrices using exact masses of product ions and corresponding neutral losses
Authors: Kaufmann Anton 
Published: June 2007

AbstractThe emergence of time‐of‐flight (TOF) and hybrid quadrupole/time‐of‐flight (Q‐TOF) mass spectrometers has offered new possibilities for determining the elemental composition of analytes present at trace levels. The mass accuracy provided by these instruments is currently in the range of 2–5 m m/z units, permitting the determination of the elemental composition of small molecules. The orthogonal information of relative isotopic abundances (RIAs) is used to reduce the number of elemental compositions that are possible, based on consideration of exact masses. Elimination of additional possible compositions has been reported when the analyte is fragmented and its resulting product ions and corresponding neutral losses are carefully analyzed. Published algorithms reduce the number of proposed precursor ions by deleting each precursor candidate which cannot be explained by summing any combination of postulated product ion and corresponding neutral loss elemental composition candidates. An extension of such algorithms is described in this paper. This approach compares not only the precursor ion with the different fragments, but tests the possible descent of any ion from all other recorded ions. This extended algorithm has been tested by processing published data. Algorithms analyzing product ion spectra can be used for real‐life data. However, there is a risk that an ion which originates from the mobile phase or from a co‐eluting matrix compound can be mathematically correlated to the investigated precursor ion. Such an incorrect correlation can lead to the deletion of a correct elemental composition. This is an important issue if TOF rather than Q‐TOF instruments are used. Therefore, ultra‐performance liquid chromatography (UPLC) and a peak deconvolution algorithm were used to generate and process TOF chromatograms in order to minimize the number of ions which are not related to the analyte precursor ion. The combined use of chromatographic deconvolution and product ion spectra has been tested and is critically discussed. Copyright © 2007 John Wiley & Sons, Ltd.
Development of a sensitive and specific liquid chromatography/mass spectrometry method for the determination of tenofovir in human plasma
Authors: Bennetto‐Hood Chantelle , Long Mary C. , Acosta Edward P. 
Published: June 2007

AbstractA sensitive and specific method for the quantitation of tenofovir (TFV) in human plasma by liquid chromatography/electrospray ionization mass spectrometry was developed and validated. Plasma samples were prepared by solid‐phase extraction performed on Waters Oasis cation‐exchange cartridges (30 mg). Chromatographic separation was performed isocratically on a reversed‐phase Waters Atlantis dC18 column (2.0 × 100 mm, 3 µm). The mobile phase consisted of a hydroxylamine/acetic acid buffer (pH 6.75) and methanol (93:7, v/v). The acquisition was performed in selected ion monitoring mode for the protonated molecular ions [M+H]+ of m/z 288.2 for TFV and 212.2 for the internal standard, zalcitibine. The method was fully validated to determine its specificity, recovery, linearity and sensitivity, accuracy and precision. The analytical range was set at 1–750 ng/mL using a 200 µL plasma sample, with a mean coefficient of determination (r2) of 0.9969. The mean accuracies for the calibration standards ranged from −5.0 to 4.3%, while the precisions were within 1.2 and 6.4%. Intra‐assay and inter‐assay mean accuracies for three quality control concentrations (2, 60, and 600 ng/mL) ranged from −6.1 to 10.7%, while the precisions were within 1.3 and 9.1%. TFV was shown to be stable under normal storage and assay conditions; no degradation was seen when stored at −20°C or −80°C for up to 6 months, and after 16 h at room temperature in the injection matrix. The present method provides an accurate, precise, and sensitive tool for TFV quantitation and was successfully applied to an external proficiency‐testing program and pharmacokinetic analysis. Copyright © 2007 John Wiley & Sons, Ltd.
Improved method for the simultaneous determination of d4T, 3TC and ddl intracellular phosphorylated anabolites in human peripheral‐blood mononuclear cells using high‐performance liquid chromatography/tandem mass spectrometry
Authors: Becher François , Pruvost Alain , Goujard Cécile , Guerreiro Catherine , Delfraissy J.‐F. , Grassi Jacques , Benech Henri 
Published: June 2007

AbstractThe original article to which this Erratum refers was published in Rapid Commun Mass Spectrom. 2002; 16: 555–565.
New estimates of the prevalence of neurological and sensory sequelae and mortality associated with congenital cytomegalovirus infection
Authors: Dollard Sheila C. , Grosse Scott D. , Ross Danielle S. 
Published: June 2007

AbstractCongenital CMV is a major cause of neurological and sensory impairment in children. Reliable estimates of the prevalence of permanent sequelae and mortality associated with congenital CMV are needed to guide development of education and prevention programmes and to gauge the financial costs associated with this disease. To calculate such estimates, this review used data solely from studies in which children with congenital CMV were identified through universal screening. Based on 15 studies with a total of 117 986 infants screened, the overall CMV birth prevalence estimate was 0.7%. The percentage of infected children with CMV‐specific symptoms at birth was 12.7%. The percentage of symptomatic children with permanent sequelae was 40–58%. The percentage of children without symptoms at birth who developed permanent sequelae was estimated to be 13.5%. The true burden of congenital CMV infection is unclear because data on important outcomes, such as visual impairment, are lacking and follow‐up of infected children has been too short to fully identify late‐onset sequelae. Therefore, the estimates of permanent sequelae associated with congenital CMV presented here are likely underestimates. Future studies should extend follow‐up of CMV‐infected children identified through universal screening and include the evaluation of visual impairment. Copyright © 2007 John Wiley & Sons, Ltd.