bluuebunny/crossref_metadata_2025_split huggingface dataset:
High‐nitrogen‐content InGaAsN films on GaAs grown by metalorganic vapor phase epitaxy with TBAs and DMHy
Authors: Sanorpim S. , Nakajima F. , Ono W. , Katayama R. , Onabe K. 
Published: May 2006

AbstractWe investigate the parameters used in the MOVPE growth of high‐N‐content Inx Ga1–x As1–y Ny films on GaAs and their structural and optical properties. The N incorporation control was found to mainly depend on the 1,1‐dimethylhydrazine (DMHy) molar flow rate and the growth temperature. With increasing the DMHy molar flow rate, the high‐resolution X‐ray diffraction measurements exhibited a clear diffraction peak shift, representing the increase in N incorporation. On the other hand, the N content was increased from y ∼ 0.5% to 3.6% with decreasing the growth temperature from 650 °C down to 500 °C. The red‐shift in both the photoluminescence (PL) peak and the photoreflactance (PR) signal (E 0 transition) with increasing N content was clearly observed. Finally, the lattice‐matched In0.06Ga0.94As0.979N0.021/GaAs film corresponding to the room‐temperature E 0 transition energy of 1.11 eV was achieved. It is noticeable that the structural and optical properties of the InGaAsN films grown using TBAs strongly depends on the N content, as in the case of corresponding films grown using AsH3. Besides, the PR spectral feature demonstrated the growth of the InGaAsN film whose bandgap is lower than 1.0 eV by using TBAs in place of AsH3. The present results show that the DMHy flow rate and the growth temperature play a critical role in the growth of high‐quality and single‐phase dilute‐nitride‐arsenide alloy semiconductors. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Waveguide mode dynamics of blue laser diodes
Authors: Pindl Markus , Schwarz Ulrich T. 
Published: May 2006

AbstractWe use a scanning near‐field microscope (SNOM) in combination with a time resolved detection scheme to measure the evolution of the near‐field and far‐field of InGaN laser diode (LD) waveguide modes. We observe lateral mode competition, filamentation, and beam steering. Here we compare the lateral mode dynamics for ridge waveguide LDs and oxide stripe LDs which are predominantly index and gain guided, respectively. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparative study on unpassivated and passivated AlGaN/GaN HFETs and MOSHFETs
Authors: Heidelberger G. , Bernát J. , Fox A. , Marso M. , Lüth H. , Gregušová D. , Kordoš P. 
Published: May 2006

AbstractIn this comparative study we investigate AlGaN/GaN‐based unpassivated and passivated HFETs and MOSHFETs with regards to DC‐, RF‐, and power‐performance. For optimal comparability, all devices emanate from the same wafer consisting of a SiC‐substrate, a 3 µm GaN‐ and a 30 nm Al0.28Ga0.72N‐layer. Devices are processed simultaneously to a large extend. Passivated devices are coated with a 10 nm thick SiO2‐layer between the electrodes, MOSHFETs contain a 10 nm thick SiO2‐layer serving as gate‐insulator underneath the gate and as conventional passivation‐layer between the electrodes. Unpassivated devices serve as reference. We present empirical evidence that MOSHFETs outperform both the conventional and the passivated HFETs with respect to DC‐, RF‐, and power‐performance, and we point out the different mechanisms responsible for the behaviour of the devices. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A comparative study of near‐UV emitting InGaN quantum wells with AlGaN and AlInGaN barriers
Authors: Zhu D. , Kappers M. J. , Costa P. M. F. J. , McAleese C. , Rayment F. D. G. , Chabrol G. R. , Graham D. M. , Dawson P. , Thrush E. J. , Mullins J. T. , Humphreys C. J. 
Published: May 2006

AbstractInGaN multiple quantum well (MQW) structures with AlGaN and AlInGaN barriers were grown on sapphire by metalorganic vapour phase epitaxy (MOVPE). The high resolution X‐ray diffraction (HRXRD) and transmission electron microscopy (TEM) characterisation results show substantial improvements in the material quality by introducing a small amount of indium into the AlGaN barriers, resulting in improved optical properties, as indicated by low‐temperature (6 K) photoluminescence (LT‐PL) spectroscopy. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
X‐ray microdiffraction imaging investigations of wing tilt in epitaxially overgrown GaN
Authors: Lübbert D. , Mikulík Petr , Pernot Petra , Helfen Lukas , Craven Michael D. , Keller Stacia , DenBaars Steven , Baumbach Tilo 
Published: May 2006

AbstractThe crystalline quality in epitaxially laterally overgrown (ELO) GaN and the amount of wing tilt is characterized on a local basis, with high spatial and angular resolution. A method of full‐field X‐ray microdiffraction imaging, termed rocking curve imaging, is used to record simultaneously a large set of local X‐ray diffraction profiles originating from sample surface areas of micrometer size. x –ω maps of diffracted intensity allow to quantify the amount of wing tilt in individual lateral ELO periods as well as to monitor the fluctuations of tilt between adjacent periods. Automated shape analysis of the full set of local rocking curves provides a means to quantitatively characterize the local crystalline perfection of GaN. The ELO window and wing regions can be clearly separated; comparison indicates an average improvement of crystal quality by a factor 3–4 due to the lateral overgrowth process. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Morphology and microstructure of a ‐plane GaN layers grown by MOVPE and by low pressure solution growth (LPSG)
Authors: Hussy S. , Meissner E. , Birkmann B. , Brauer I. , Off J. , Scholz F. , Strunk H. P. , Müller G. 
Published: May 2006

AbstractIn this paper a ‐plane GaN‐layers, grown by two different techniques are compared, mainly focusing on the surface morphology and microstructure of the samples: Layers grown by metal organic vapor phase epitaxy (MOVPE) exhibit a flat surface interrupted by a certain number of pits with triangular shape. In contrast, specimens processed by LPSG developed a rough surface with a roof like morphology. The morphology is discussed in view to the facetting behaviour of the GaN. The observed thickness of the layers implies, that growth in this direction is slightly faster compared to the regular c ‐plane growth. TEM investigations showed that the microstructure of the a ‐plane samples is dominated by a high density of dislocations and stacking faults. In photoluminescence measurements a slightly different characteristic was seen for the materials grown by the two techniques. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Deep ultraviolet light‐emitting diodes
Authors: Hu X. , Deng J. , Zhang J. P. , Lunev A. , Bilenko Y. , Katona T. , Shur M. S. , Gaska R. , Shatalov M. , Khan A. 
Published: May 2006

AbstractWe report on the development of AlGaN‐based deep UV light emitting diodes (LEDs) with emission wavelengths from 254 to 340 nm, focusing on the improvement of 280 nm LEDs efficiency. Under optimal device structure the UV LEDs efficiency was found to strongly depend on the AlGaN material quality. Milliwatt‐power level LEDs were demonstrated for the 254–340 nm spectral range, and for 280 nm LEDs powers reaching 2.5 mW was achieved at 20 mA DC. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Strain‐relaxation in NH3‐source molecular beam epitaxy of AlN epilayers on GaN epitaxial templates
Authors: Koyama T. , Sugawara M. , Uchinuma Y. , Kaeding J. F. , Sharma R. , Onuma T. , Nakamura S. , Chichibu S. F. 
Published: May 2006

AbstractTemporal evolution of surface morphology in AlN epilayers grown by NH3‐source molecular beam epitaxy on the GaN/(0001) Al2O3 epitaxial templates was correlated with changes in the degree of the residual strain and the layer thickness. They began to crack for the thickness as thin as 10 nm. However, atomic‐layer step‐and‐terrace surface structures were maintained for the thickness up to 32 nm. Tensile biaxial stress decreased with further increase in the thickness due to the lattice relaxation, which caused surface roughening. An 1580‐nm‐thick, nearly strain‐compensated AlN epilayer, of which threading dislocation density was reduced down to 6 × 109 cm–2, exhibited excitonic photoluminescence peaks at 6.002 and 6.023 eV at 9 K and a near‐band‐edge peak at 5.872 eV at 293 K. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparison of degradation mechanisms of blue‐violet laser diodes grown on SiC and GaN substrates
Authors: Furitsch M. , Avramescu A. , Eichler C. , Engl K. , Leber A. , Miler A. , Rumbolz C. , Brüderl G. , Strauß U. , Lell A. , Härle V. 
Published: May 2006

AbstractIn this work we present degradation studies of GaN based blue‐violet laser diodes grown on different substrates. By replacing the SiC substrate by GaN substrate, we change from hetero to homo epitaxy, while the threading dislocation density (TDD) is reduced by 3 orders of magnitude. A detailed analysis of small signal I –V curves shows an increase of non radiative (NR) recombination centers during aging for laser diodes on SiC substrate. This was not observed for lasers on GaN substrate due to the reduced TDD and therefore reduced number of diffusion channels for Mg‐atoms, acting as NR recombination centers in the active region. With an improved epitaxial structure on GaN substrate, we increased the lifetime of our lasers by a factor of 10. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Towards identification of degradation mechanisms in InGaN laser diodes grown on bulk GaN crystals
Authors: Marona L. , Riemann T. , Christen J. , Świetlik T. , Franssen G. , Wiśniewski P. , Leszczyński M. , Prystawko P. , Grzegory I. , Suski T. , Porowski S. , Czernecki R. , Perlin P. 
Published: May 2006

AbstractIn this work we present a reliability study of low dislocation density InGaN laser diodes fabricated on high‐pressure grown GaN monocrystaline substrates. The aging process was performed under pulse current conditions. Degradation of these devices manifests primarily in the increase of the threshold current. Interestingly, the differential efficiency of lasers remains stable at all times. The aging time dependence of the increase of the threshold current precisely follows a square root dependence. These observations suggest that the degradation results from the enhancement of the nonradiative recombination within the device active layers and is related to point defect diffusion. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Development of AlInGaN based blue–violet lasers on GaN and SiC substrates
Authors: Rumbolz C. , Brüderl G. , Leber A. , Eichler C. , Furitsch M. , Avramescu A. , Miler A. , Lell A. , Strauß U. , Härle V. 
Published: May 2006

AbstractWe present a process for high quality InGaN laser diodes on free standing GaN substrates with high reproducibility. We demonstrate a self‐aligned process to contact lasers with ridge width <2 μm. The stability of the process allows us to optimize the epitaxial structure on GaN substrates and we achieve cw‐threshold current densities of 2.9 kA/cm2 for 10 μm wide ridges and 4.7 kA/cm2 for 1.5 μm wide ridges. Cw‐slope efficiencies of 1.0 W/A are achieved for both widths. Beside this we notice a reduction of the ideality factor and the forward bias linked to an improvement of the epitaxial interfaces. For maximum optical output we could achieve 3.4 W from one output facet at pulsed operation and a catastrophic optical mirror damage (COMD) level of 67 MW/cm2. Furthermore we observe a dependency of the COMD level from the pulse width corresponding to filament formation. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical study of the AlGaN/GaN high electron mobility transistor structures
Authors: Lin D. Y. , Lin W. C. , Shiu J. J. 
Published: May 2006

AbstractWe present an optical study on three Alx Ga1–x N/GaN high electron mobility transistor structures, which were grown by metalorganic chemical vapor deposition (MOCVD) on sapphire substrates, with different Al compositions using contactless electroreflectance (CER), piezoreflectance (PzR) and surface photovoltage spectroscopy (SPS). The Al composition x can be determined from the band gap energy of Alx Ga1–x N layer observed in CER and PzR spectra. The determination of the built‐in electric field strength in the barrier layer (F) has been done by the analysis of Franz–Keldysh oscillations (FKOs) above the Alx Ga 1–x N band gap in CER spectra. A broad feature appeared at energies above the band gap of GaN was observed in each CER, PzR and SPS spectrum. We believe that it is related to the two‐dimensional electron gas (2DEG). The energy of the broad 2DEG minimum roughly corresponds to the Fermi energy plus the band gap. The Hall‐effect measurements have also been carried out in van der Pauw geometry at room temperature to reveal the sheet carrier density (n s). For the sample with lowest alloy composition (x = 0.07) the analysis of the FKOs yields F = 316 kV/cm at room temperature. When the temperature was cooled down to 50 K the electric field strength decreases to 188 kV/cm. This result can be explained by the change of piezoelectric polarization. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Strain and microstructure in Fe‐doped GaN layers grown by low pressure metalorganic vapour phase epitaxy
Authors: Azize M. , Leroux M. , Laugt M. , Gibart P. , Bougrioua Z. 
Published: May 2006

AbstractIn order to get semi‐insulating GaN layers with a low dislocation density on sapphire, two kinds of Fe doping were explored by low pressure metalorganic vapour phase epitaxy (LP‐MOVPE): the modulation doping (MD) and the continuous doping (CD). The high crystalline quality and the semi‐insulating character are obtained in the case of the Fe‐MD layers. The effect of Fe doping on the strain was investigated in both kind of layers (MD and CD) by X‐ray diffraction, photoluminescence and reflectivity. The lattice parameters are functions of the iron doping level, whatever the doping mode. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Selective‐area growth and fabrication of recessed‐gate GaN MESFET using plasma‐assisted molecular beam epitaxy
Authors: Hong Seung Jae , Chapman Patrick , Krein Philip T. , Kim Kyekyoon (Kevin) 
Published: May 2006

AbstractFor the first time, selective‐area growth (SAG) technique has been developed using plasma‐assisted molecular beam epitaxy (PAMBE), enabling fabrication of a recessed‐gate structure for the metal‐semiconductor field‐effect transistor (MESFET) without etching. On patterned SiO2 samples, polycrystalline GaN and single crystal n+‐GaN were observed to grow in the masked and unmasked regions, respectively. The regrown layers were analyzed using AFM. Ohmic contact formed on the n+‐GaN exhibited a vastly improved contact resistivity of 1.8 × 10–8 Ω cm2, giving rise to excellent device characteristics including a peak drain current of 360 mA/mm and a maximum transconductance of 46 mS/mm. The advantages of SAG were further investigated by comparing the dc characteristics of recessed‐gate and unrecessed MESFET. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimization of AlGaN/GaN HEMTs for high frequency operation
Authors: Palacios T. , Dora Y. , Chakraborty A. , Sanabria C. , Keller S. , DenBaars S. P. , Mishra U. K. 
Published: May 2006

AbstractIn this paper, the structure and processing of AlGaN/GaN high electron mobility transistors have been optimized for maximum small signal gain at high frequencies. The effect of the gate resistance, gate‐to‐drain capacitance and output conductance on the power gain cut‐off frequency, f max, of the devices has been experimentally studied. The reduction of the gate width allowed a 4‐fold decrease in gate resistance which resulted in almost a 100% increase in f max. To minimize C gd, Γ‐shape gates have been processed instead of the conventional T‐shape submicron gates. Finally, to reduce the output conductance, the confinement of the 2‐dimensional electron gas was increased by using an ultra‐thin InGaN layer below the GaN channel. This InGaN back‐barrier caused a 2‐fold improvement in output conductance which allowed a 20% increase in f max. By optimizing all these parameters, AlGaN/GaN transistors with a record f max of 230 GHz were obtained. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Crystal quality and growth evolution of aluminum nitride on silicon carbide
Authors: Moe Craig G. , Wu Yuan , Keller Stacia , Speck James S. , DenBaars Steven P. , Emerson David 
Published: May 2006

AbstractHigh quality base layer aluminum nitride films have become increasingly desirable with the advent of deep ultraviolet (<280 nm) emitters for water purification, solid state lighting, and biochemical detection applications. In this study, the influence of the MOCVD growth conditions on the structural properties of aluminum nitride grown on silicon carbide, both as‐delivered and chemomechanically polished, was studied. Pre‐deposition nitridation of the SiC substrate, growth temperature, growth rate, ammonia flow (V/III ratio), and gallium surfactants were explored. Films were analyzed with transmission electron microscopy (TEM), atomic force microscopy (AFM), and X‐ray diffraction. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Epitaxial lateral overgrowth of AlN layers on patterned sapphire substrates
Authors: Nakano K. , Imura M. , Narita G. , Kitano T. , Hirose Y. , Fujimoto N. , Okada N. , Kawashima T. , Iida K. , Balakrishnan K. , Tsuda M. , Iwaya M. , Kamiyama S. , Amano H. , Akasaki I. 
Published: May 2006

AbstractEpitaxial lateral overgrowth (ELO) of low‐dislocation‐density AlN layers on trench‐patterned sapphire substrates is demonstrated for the first time. Sapphire (0001) substrates with trench patterns formed along two different directions, 〈10$ 10 \bar 10 $0〉 and 〈11$ 11 \bar 20 $0〉, were used. We can obtain fully coalesced AlN only on the sapphire substrate having 〈11$ 11 \bar 20 $0〉 trenches. The dislocation density of ELO‐AlN is as low as 6.7 × 108 cm–2. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
MOVPE growth and optical characterization of GaAsN films with higher nitrogen concentrations
Authors: Nakajima F. , Sanorpim S. , Ono W. , Katayama R. , Onabe K. 
Published: May 2006

AbstractWe have successfully grown high‐N‐content GaAsN films up to 5.1% on GaAs(001) substrates using tertiarybutylarsine (TBAs) as the As precursor by metalorganic vapour phase epitaxy (MOVPE). The narrow X‐ray diffraction (XRD) peaks and clear Pendellosung fringes indicate that the GaAsN/GaAs interface is fairly flat and the GaAsN layers are uniform. By the photoluminescence (PL) measurement at 10 K, the clear PL peaks related to the near‐band‐edge transition could be detected and the bandgap energy was red‐shifted to 1.16 eV in 1.9%‐N GaAsN film. But, in higher N‐content films no peak could be detected. So, post growth annealing in the reactor was applied to 4.7% and 5.1%‐N films, and resulted in an enhancement of the PL peak intensity, and the bandgap energy of 5.1%‐N film was consequently determined to be 0.95 eV at room temperature. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Self‐regulating mechanism of InN growth on GaN(0001) by molecular beam epitaxy; from nanostructures to films
Authors: Dimakis E. , Iliopoulos E. , Tsagaraki K. , Georgakilas A. 
Published: May 2006

AbstractThe surface kinetics of InN growth on GaN(0001) by plasma assisted molecular beam epitaxy was investigated. The surface coverage of the GaN(0001) surface by InN islands and the corresponding islands' growth rate along the [0001] direction, were studied as a function of substrate temperature. Both quantities were found to behave non‐monotonically with substrate temperature due to the interplay between In‐adatoms' surface migration and InN decomposition rate. In the range of temperatures were In‐adatoms' mobility is sufficient, a self‐regulating mechanism of InN islands' shape takes place. This mechanism insures stoichiometric ratio of In and N adatoms on the top (0001) surface of the islands. These findings are summarized in a physical model that describes the growth of InN on GaN(0001) surfaces. In the context of the model, four distinct growth regimes are defined as a function of substrate temperature for a given In/N flux ratio. The exploitation of the self‐regulating mechanism led to successful growth of InN films with good structural, morphological and electrical properties. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Gallium nitride based micro‐cavity light emitting diodes emitting at 498 nm
Authors: Pattison P. Morgan , Sharma Rajat , David Aurelian , Waki Ichitaro , Weisbuch Claude , Nakamura Shuji 
Published: May 2006

AbstractA gallium nitride based micro‐cavity light emitting diode emitting at a peak wavelength of 498 nm has been fabricated. The epitaxial structure was grown by metalorganic chemical vapor deposition, and the device was fabricated using a laser lift‐off process. Cavity thinning was carried out using reactive ion etching until a cavity length of roughly 830 nm (corresponding to a cavity order of ∼8 for λ = 498 nm in GaN) was achieved. Electroluminescence measurements of the micro‐cavity device show a narrowed spectral width compared to the un‐thinned device, and angularly resolved spectral measurements yielded a spectral shift, evincive of micro‐cavity effects. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
InN growth on sapphire using different nitridation procedures
Authors: Drago M. , Werner C. , Pristovsek M. , Pohl U. W. , Richter W. 
Published: May 2006

AbstractWe studied optimal sapphire nitridation conditions with ammonia for the metal‐organic vapor phase epitaxy of InN using in‐situ spectroscopic ellipsometry (SE). SE indicates the formation of a complete AlN‐containing layer on top of the sapphire surface during the first 45 s of nitridation. Further nitridation leads to a growth of the AlN‐like layer by nitrogen diffusion and to roughening. Successively, a set of high quality InN films were grown onto sapphire substrates after different nitridation duration. Electronic characterisation clearly indicates optimum InN quality for 45 s of sapphire nitridation, i.e. when only the sapphire surface is nitridated, as determined by in‐situ SE. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Crack free monolithic nitride vertical‐cavity surface‐emitting laser structures and pillar microcavities
Authors: Lohmeyer Henning , Sebald Kathrin , Kruse Carsten , Kröger Roland , Gutowski Jürgen , Hommel Detlef , Wiersig Jan , Jahnke Frank 
Published: May 2006

AbstractWe report on the successful fabrication and optical investigation of monolithicly grown GaN based vertical‐cavity surface‐emitting laser structures featuring quality factors of 250. Short‐period AlN/InGaN superlattices are used for the low‐index layers of the distributed Bragg reflectors. Pillar microcavities are realized by focused‐ion‐beam etching. Micro‐photoluminescence measurements reveal the longitudinal and transversal mode spectra of the cavities in good agreement with theoretical calculations based on a vectorial transfer matrix method. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Novel devices based on the combination of nitride and II–VI materials
Authors: Murai A. , Kruse C. , McCarthy L. , Mishra U. K. , DenBaars S. P. , Hommel D. 
Published: May 2006

AbstractWe demonstrate the direct wafer bonding of GaN and ZnSe‐based materials. We report on the structural, optical, and electrical characteristics of InGaN/GaN light‐emitting diodes (LEDs) and ZnSe‐based II–VI materials combined by direct wafer bonding. Reflectivity, transmission electron microscopy (TEM), and current–voltage (I –V ) measurements were performed. The bonded sample exhibited a higher reflectivity at the wavelength of 510 nm than a control LED with an Al cap. Cross‐sectional TEM revealed a uniform wafer‐bonded interface with no voids or cavities for the low temperature sample, while the sample bonded at a higher temperature was observed to have lens‐shaped cavities at semiconductor interfaces. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)