bluuebunny/crossref_metadata_2025_split huggingface dataset:
Materials Characterization on Optically Pumped InGaN/GaN Lasers by Farfield Measurements and Fourier Analysis of the Emission Spectrum
Authors: Hofstetter D. , Thornton R. L. , Romano L. T. , Bour D. P. , Johnson N. M. 
Published: April 2011

AbstractWe report materials characterization on optically pumped InGaN/GaN lasers by farfield and spectral measurements. Through a comparison between measured and calculated farfield data for an In0.15Ga0.85N/In0.05Ga0.95N multi quantum well laser structure with AIGaN cladding layers, we could extract important information about the optical confinement in the transverse direction. The analysis of Fourier-transformed emission spectra of our devices allowed us to make qualitative statements about the material quality in terms of surface pits and cracks. We believe that optical pumping with these supplementary techniques is an important and powerful tool which helps to overcome critical material quality requirements in gallium-nitride.
Breakdown Behavior of Aigan Msm uv Photodetectors
Authors: Liang S. , Liu Y. , Lu Y. , Schurman M. , Tran C. A. , Ferguson I. 
Published: April 2011

AbstractGaN is an attractive wide bandgap semiconductor material for optoelectronic device applications at blue and UV wavelengths. The breakdown behavior of interdigital MSM type of AlGaN UV photodetectors (PDs) are reported here. The A1GaN was deposited using MOCVD technique. The MSM devices were fabricated using undoped AlGaN (Al composition is 0.13) epitaxial layer on sapphire substrate. Au/Ti metallization was patterned as metal electrodes on AlGaN. Very high UV responsivity of the devices was achieved at DC bias voltage in the range of 60–140V depending on the device dimensions. The breakdown voltage exhibits a negative temperature coefficient. The relationship between the breakdown voltage and device dimensions has been investigated using both of I-V, C-V characteristics. It has been found that annealing of the contact modifies the device characteristics, in particular, the breakdown behaviors.
Wide Gan Stripes by Lateral Growth in Metalorganic Vapor Phase Epitaxy
Authors: Kimura A. , Sasaoka C. , Sakai A. , Usui A. 
Published: April 2011

AbstractWe investigated the growth conditions for enhancing epitaxial lateral overgrowth (ELO) of GaN stripes selectively grown by low-pressure metalorganic vapor phase epitaxy. The ELO was enhanced for GaN <1100> stripes and with a small trimethylgallium flow-rate. This tendency did not depend on mask materials. The cross-sectional shape of the GaN <1100> stripes was trapezoidal for SiO2 masks, and rectangular for silicon nitride (SiN2) masks in a certain growth condition. A low dislocation density in the ELO region was obtained not only for the SiO2 masks but also for the SiN2 masks.
Application of Blue Diode Lasers to Printing
Authors: Bringans R. D. 
Published: April 2011

AbstractThe availability of blue diode lasers would have a significant impact on several printing applications. The laser printing market is moving towards higher resolutions and higher print speeds. The optical systems for polygon scanner laser printers are diffraction limited and therefore to improve the optical resolution it is very advantageous to reduce the wavelength of the scanning laser beam from that of the IR or red lasers currently being used. The other printing application of blue lasers is exposure of film, an area where argon ion lasers are currently being used. Replacement of these by diode lasers would potentially lower system costs. In this paper, the applications of blue lasers to printing will be outlined and the technical requirements that the lasers will need to satisfy will be discussed.
MOVPE Growth of GaPAsN Quaternary Alloys Lattice-Matched to GaP
Authors: Biwa Goshi , Yaguchi Hiroyuki , Onabe Kentaro , Shiraki Yasuhiro 
Published: April 2011

AbstractGaP1-x-yAsyNx. (x ∼,2.3%, 0< y <19%) quaternary alloy semiconductor films on GaP substrates have been successfully grown by metalorganic vapor phase epitaxy (MOVPE). With the fixed supplies of trimethylgallium(TMG), AsH3 and dimethylhydrazine(DMHy) during the growth, the As concentration in the solid increased with increasing AsH3 supply, while the N concentration was almost unaffected. It has been demonstrated that the crystalline quality of the alloy films is much improved with the close lattice-matching to the GaP substrate, giving a superior surface morphology without any cross-hatches, a much narrower x-ray diffraction linewidth, and a significantly higher photoluminescence(PL) intensity.
Si and Mg Doped Gan Layers Grown by Gas Source Molecular Beam Epitaxy Using Ammonia
Authors: Grandjean N. , Massies J. , Leroux M. 
Published: April 2011

AbstractThe growth of GaN layers was carried out on c-plane sapphire substrates by molecular beam epitaxy (MBE) using NH3. Undoped GaN layers were grown at 830°C with growth rates larger than 1 μm/h. Optical properties are characteristics of high quality GaN material and the linewidth of x-ray diffraction (0002) rocking curve is less than 350 arcsec. N- and p-type doping were achieved by using solid sources of Si and Mg. No post-growth annealing was needed to activate the Mg acceptors. As-grown GaN:Mg layers exhibit hole concentrations of 3×1017 cm−3and mobilities of 8 cm2/Vs at 300 K. Light emitting diodes (LEDs) based on GaN p-n homojunction have been processed. The turn on voltage is 3 V and the forward voltage is 3.7 V at 20 mA. The 300 K electroluminescence (EL) peaks at 390 nm.
Effect Of Atomic-Hydrogen Treatment Of (001) Gaas Substrate At “High Temperatures” On Rf Plasma-Assisted Molecular Beam Epitaxy Of Cubic Gan
Authors: Yoshikawah A. , Nagano H. , Qiny Z. X. , Sugure Y. , Jia A. W. , Kobayashi M. , Shimotomai M. , Kato Y. , Takahashi K. 
Published: April 2011

AbstractsGrowth of high quality c-GaN on atomic-H treated (001) GaAs was examined by rf plasma-assisted MBE. First the initial growth stages (atomic-H treatment of GaAs, nitridation/deposition of a thin GaN buffer layer, the post deposition annealing of the buffer layer, and epitaxy of c-GaN) were studied by RHEED and AFM observations. It was found that atomically flat GaAs surface with one monolayer-height steps and ragged step edges could be obtained by the atomic-H treatment at high temperatures. It was found that the atomic-H treated GaAs surface was preferable to grow high quality c-GaN; the FWHM of the X-ray rocking curve for the (002) c-GaN was as small as 70 – 90 arcsec.
GaN PN-Structures Grown by Hydride Vapor Phase Epitaxy
Authors: Nikolaev A. E. , Melnik YU. V. , Kuznetsov N. I. , Strelchuk A. M. , Kovarsky A. P. , Vassilevski K. V. , Dmitriev V. A. 
Published: April 2011

AbstractFor the first time, GaN pn-junctions were fabricated by hydride vapor phase epitaxy. GaN pn-structures were grown directly on 6H-SiC substrates without any buffer layer. Undoped GaN layers were n-type with Nd-Naconcentration ranged from 1×1017to 5×1018cm−3. Magnesium was used as an acceptor to grow p-type GaN layers. Mg atomic concentration determined by secondary ion mass spectroscopy ranged from 5×1019to 5×1020cm−3. As-grown GaN layers doped with Mg were p-type, and p-type conductivity was improved by post-growth anneal. Mesa diodes with a vertical current flow geometry were formed by reactive ion etching. The position of the GaN pn-junction was determined by the electron beam induced current method. The electrical characteristics of the pn diodes were studied. Electroluminescence from the pn diodes was measured.
Homoepitaxial Growth of GaN Using Seeded Supersonic Molecular Beams
Authors: Chen E. , Zhang S. , Michel A. , Davis R. F. , Lamb H. H. 
Published: April 2011

AbstractHomoepitaxial growth of GaN on MOCVD-grown GaN/AlN/6H-SiC substrates was investigated using NH3-seeded supersonic molecular beams and an effusive Ga source. Ga-limited growth is observed at 730 and 770°C for incident Ga fluxes ≤ 1.2×1015 cm−2 s−1 using a 0.25 eV NH3 beam. A Ga incorporation efficiency of 20–25% is observed under these conditions. Increasing NH3 kinetic energy in the 0.25 to 0.61 eV range results in a modest increase in the GaN growth rate which we ascribe to an enhancement in NH3 reactivity. A concomitant increase in surface roughness is observed with increasing GaN growth rate.
Pulsed Laser Deposition of Highly Crystalline Gan Films on Sapphire
Authors: Vispute R. D. , Talyansky V. , Chupoon S. , Enck R. , Dahmas T. , Ogale S. B. , Sharma R. P. , Venkatesan T. , Li Y. X. , Salamanca-Riba L. G. , Iliadis A. A. , He M. , Tang X. , Halpern J. B. , Spencer M. G. , Khan M. A. , Jones K. A. , Bel'kov V. , Botnaryuk V. , Diakonu I. , Fedorov L. , Zhilyaev Y. 
Published: April 2011

AbstractWe report high quality epitaxial growth of GaN film by pulsed laser deposition technique. In this method, a KrF pulsed excimer laser was used for ablation of a polycrystalline, stoichiometric GaN target. The ablated material was deposited on a substrate kept at a distance of ∼ 7 cm from the target surface and in an NH3 background pressure of 10−5 Torr and temperature of 750°C. The films (∼0.5 μm thick) grown on AIN buffered sapphire showed a x-ray diffraction rocking curve FWHM of 4–6 arc minutes. The ion channeling minimum yield in the surface region was ∼3% indicating a high degree of crystallinity. The optical band gap was found to be 3.4 eV. The epitaxial films were shiny, and the surface RMS roughness was ∼ 5–15 nm. The electrical resistivity of these films was in the range of 10−2–102 Ω-cm with a mobility in excess of 60 cm2V-1s−1 and carrier concentration of 1017–1019cm−3.
Lateral Epitaxy Formation Mechanism And Microstructure Of Selectively Grown Gan Structures
Authors: Zheleva Tsvetanka , Nam Ok-Hyun , Griffin Jason D. , Bremser Michael D. , Davis Robert F. 
Published: April 2011

AbstractThe microstructure and the lateral epitaxy mechanism of formation of homoepitaxially and selectively grown GaN structures within windows in SiO2 masks have been investigated by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Three types of samples and each of their microstructures as a function of the geometry of the mask pattern and the selective growth parameters have been studied: GaN pyramids, GaN stripes oriented along [1100] and [1120] directions, and GaN continuous layers. Observations via TEM showed in all three types of samples that the laterally overgrown GaN exhibit four-to-six orders of magnitude reduction in the dislocation density compared to the vertically grown GaN films. Owing to the lateral epitaxy, the threading dislocations bend when the growth front changes from vertical to lateral, thus changing their character from being mostly threading dislocations of mixed or edge character, to being basal plane dislocations with lines parallel to the interfacial planes. The underlying GaN provided the crystallographic template for the initial vertical selective growth through the openings (windows) in the SiO2 mask. The GaN structures in these areas had a threading dislocations density of 108-1010 cm−2. Lateral growth of the GaN films over the amorphous SiO2 mask, resulted in a reduction of the dislocation density to <106 cm−2. The primary materials source for both the vertical and lateral growth of the structures was the vapor phase. Essentially no GaN deposited on the SiO2 because of the very low sticking coefficients of Ga and N species on SiO2. Thermal stress relaxation is responsible for the final morphology and microstructure in these selectively grown structures.
Crystal Defects In Gan On (0001) Sapphire
Authors: Johnson Matthew T. , Mao Zhigang , Carter C. Barry 
Published: April 2011

AbstractDefect structures in GaN thin films grown on (0001) sapphire have been studied using a combination of different transmission electron microscopy (TEM) techniques. Two fundamentally different types of defects are found in these films. Planar defects which lie on planes perpendicular to the growth surface are common. In some regions of the films, other planar defects are present which run parallel to the surface of the substrate. The terminology used to describe these different defects varies quite widely in the literature and includes combinations of antiphase (inversion) domain boundaries and stacking faults. The second type of defect is generally referred to as a threading dislocation since many thread through the whole thickness of the film. Dislocations with different Burgers vectors have been identified in this work and in previous studies; these dislocations usually have a component of their Burgers vector lying normal to the (0001) plane. The overall defect structures in these films have been characterized using conventional bright-field and dark-field imaging. The detailed structure of the individual defects have been examined using weak-beam microscopy both in plan view and in cross section. This paper illustrates the different types of defects, both planar and linear, compares them to defects which have been characterized more thoroughly in related materials, and discuss the nomenclature of the different defect configurations.
Transmission Electron Microscopy Study of Room Temperature Lasing Epitaxial ZnO Films on Sapphire
Authors: Wang N. , Fung K. K. , Yu P. , Tang Z. K. , Wong G. K. L. , Kawasaki M. , Ohtomo A. , Koinuma H. , Segawa Y. 
Published: April 2011

AbstractWe have studied the microstructures of lasing and non-lasing ZnO films on sapphire in plan-view and cross-section by transmission electron microscopy (TEM). While ZnO films in general are made up of cloumnar close-packed c-axis misoriented nanocrystals, the misorientation in nonlasing film, typically 5°, is considerably larger than lasing film, typically less than 1°. A rather high density of pinholes or nanotubes is associated with the highly misoriented films. The misorientation between adjacent grains is taken up by grain boundary dislocations. Room temperature lasing films contain a high density of threading boundary edge dislocations, in excess of 1010 cm−2. But faceting in the columnar nanocrystals is not well developed so that the grain boundaries are not clearly visible. Tilting of (0001) lattice planes between grains originating from substrate surface step and growth fault step, however, has been observed in high resolution electron microscopy (HREM) images.
Amorphous Domains in GaN Layers Grown on 6H-SiC by MBE
Authors: Vermaut P. , Potin V. , Ruterana P. , Hairme A. , Nouet G. , Salvador A. , Morkoç H. 
Published: April 2011

AbstractUsing N-rich growth conditions, amorphous domains were formed in the initial stage of a cyclotron assisted MBE of GaN grown over 6H-SiC (0001) without any buffer layer. These domains are facetted along {1010} prismatic planes. Their density is about 1010cm-2 and they are mainly located in a 50 nm layer close to the substrate surface.
Low-Angle and High-Angle Grain Boundaries in AIN/GaN Layers Grown on (0001) Sapphire by MBE
Authors: Potin V. , Ruterana P. , Hairie A. , Nouet G. 
Published: April 2011

AbstractAIN buffer and GaN layers grown on (0001) sapphire substrate by molecular beam epitaxy have been analysed by high resolution electron microscopy. They are found to be made of mosaic grains rotated around the c-axis by angles in the range of 0-20°. According to the value of the rotation angle, these boundaries can be classified as low-angle and high-angle grain boundaries. Some of these high-angle grain boundaries correspond to special misorientations which can be described in terms of coincidence site lattice. For one of these grains, the rotated angle is equal to 18.94° that is very close to the coincidence orientation, sigma = 31 with a rotation angle equal to 17.89°. This leads to a new epitaxial relationship (0001)sap// (0001)AIN and [1120]sap//[2130]AIN.
Tem Study of Interfaces And Defects in Mocvd-Grown Gan on Sic on Simox
Authors: Zhou W. L. , Pirouz P. , Namavar F. , Colter P. C. , Yoganathan M. , Leksono M. W. , Pankove J. I. 
Published: April 2011

AbstractSiC was grown on the top Si layer of SIMOX by carbonization followed by chemical vapor deposition (CVD). Subsequently, GaN was deposited on the SiC by metalorganic (MO)CVD to produce a GaN/SiC/Si/SiO2/Si multilayer structure. This multilayer film was investigated by conventional transmission electron microscopy (TEM) and high resolution (HR)TEM using cross-sectional thin foils. The GaN layer was found to consist of predominately hexagonal gallium nitride (h-GaN), and a smaller fraction of cubic GaN (c-GaN) crystallites. The orientation relationship between most of the h-GaN grains and cubic SiC (3C-SiC) was found to be (0001)GaN//(1I1)sic; [1120]GaN//[110]SiC, while most of the c-GaN grains had an orientation relationship (001)GaN//(001)SiC; [110]GaN//[110]SiC with respect to the 3C-SiC substrate. The hexagonal grains of GaN were found to grow as two variants. In this paper, the defects in both h-GaN and c-GaN are characterized and discussed.
Effect of Nitridation and Buffer in GaN Films Grown on A-Plane (11-20) Sapphire
Authors: Doppalapudi D. , Iliopoulos E. , Basu S. N. , Moustakas T. D. 
Published: April 2011

AbstractIn this paper, we report on a systematic study of GaN growth on the A-plane sapphire by plasma-assisted MBE. The effects of plasma nitridation of the substrate and the growth of a low temperature GaN buffer on the structure and optoelectronic properties of the films are addressed. TEM studies indicate that films grown on substrates which were not nitridated prior to growth have a significant fraction of zinc-blende domains and poor orientational relation with the substrate. On the contrary, nitridation leads to films with superior structural and optoelectronic properties. The low temperature GaN buffer, grown on nitridated substrates, was found to also have a pronounced effect on the optoelectronic properties of the GaN films, especially in those with low carrier concentrations. The correlation between TEM and photoluminescence studies suggest that the transition at 3.27 eV can be attributed to the cubic domains in the films.
Magnetoluminescence and Resonant Electronic Raman Scattering Investigation of Donors and Excitons in Hydride Vpe and Mocvd GaN
Authors: Skromme B. J. , Jayapalan J. , Wang D. , Sankey O. F. 
Published: April 2011

AbstractThe donor and exciton states in ultra high-quality heteroepitaxial GaN grown by hydride vapor phase epitaxy (HVPE) and metalorganic chemical vapor deposition (MOCVD) on sapphire substrates are investigated using low temperature photoluminescence (PL), reflectance, magnetospectroscopy in fields up to 12 T, and resonant electronic Raman scattering (RERS). The A free exciton is confirmed to have a binding energy of about 26.4 meV, independent of strain in the material. Bound n=2 exciton peaks are distinguished in the PL spectrum by their thermalization and sample dependence. The Si donor is shown to have a binding energy of about 21 meV using Si-doped HVPE samples grown at Epitronics. Up to five additional residual donor species are observed when comparing various HVPE and MOCVD samples. Pronounced temperaturedependence of the two-electron satellites is observed, suggesting the existence of unresolved excited rotator states of the neutral donor-bound exciton. Highly resolved magnetic splitting patterns are observed in the two-electron satellites. A nonperturbative theory of these donor splittings is developed, including anisotropy. Resonant electronic Raman scattering from residual donors is reported, and yields improved linewidths compared to PL.
Characterization Of Bulk, Polycrystalline Indium Nitride Grown At Sub-Atmospheric Pressures
Authors: Dycka Jeffrey S. , Kash Kathleen , Kim Kwiseon , Lambrecht Walter R. L , Hayman Cliff C. , Argoitia Alberto , Grossner Michael T. , Zhouc Weilie L. , Angus John C. 
Published: April 2011

AbstractPolycrystalline, wurtzitic indium nitride was synthesized by saturating indium metal with atomic nitrogen from a microwave plasma source. Plasma synthesis avoids the high equilibrium pressures required when molecular nitrogen is used as the nitrogen source. Two types of growth were observed: 1) small amounts of indium nitride crystallized from the melt during cooling and 2) hexagonal platelets formed adjacent to the In metal source on the crucible sides. The mechanism of this latter growth is not established, but may involve transport of indium as a liquid film. The crystals were characterized by electron diffraction, X-ray diffraction, elemental analysis, scanning electron microscopy, and Raman spectroscopy. Lattice parameter and Raman active phonon modes are reported and compared with calculations based on the full-potential linear muffin-tin orbital method (FP-LMTO).
GaN Room Temperature exciton Spectra by Photovoltaic Measurement
Authors: Liu W. , Li M. F. , Chua S. J. , Zhang Y. H. , Uchida K. 
Published: April 2011

AbstractExciton absorption peak has been clearly observed at room temperature by photovoltaic spectra, on a GaN layer grown on (0001)-plane Sapphire by metalorganic chemical vapor deposition. From the spectra, we obtained A and B exciton transition energies to be 3.401 eV, 3.408 eV, and the energy gap to be 3.426 eV in wurztite GaN, respectively. We have also performed photovoltaic measurements with various incidence angles of light, and observed the polarization behavior of exciton absorption in GaN. Finally, we used UV-polarizer to further confirm the polarization properties of GaN. In conjuction with previous room temperature photoreflectance measurements, this work provide direct and reliable assessment of the excitonic properties and crystal quality of GaN semiconductor layers.
Photoluminescence Properties Of Gan/AlGaN Multiple Quantum Well Microdisks
Authors: Mair R. A. , Zeng K. C. , Lin J. Y. , Jiang H. X. , Zhang B. , Dai L. , Tang H. , Botchkarev A. , Kim W. , Morkoc H. 
Published: April 2011

AbstractAn array of microdisks with diameter of about 9 μm and spacing of 50 μm has been fabricated by dry etching from a 50 Å/50 Å GaN/AlxGa1-xN (x∼ 0.07) multiple quantum well (MQW) structure grown by reactive molecular beam epitaxy. The as-grown MQWs and the microdisk structures have been studied by picosecond time-resolved photoluminescence (PL) spectroscopy. PL emission spectra and decay dynamics were measured at various temperatures and pump intensities. With respect to the original MQWs, we observe strong enhancement of the transition intensity and lifetime for both the intrinsic and barrier transitions. The intrinsic transition is excitonic at low temperatures and exhibits an approximate 10 fold increase in both lifetime and PL intensity upon formation of the microdisks. The exciton transition magnitude diminishes rapidly with increased temperature however, while the enhanced lifetime shows little change. At room temperature the dominant GaN well transition is found to be band-to-band in nature as evidenced by effective band gap shrinkage and band-filling effects seen within the PL spectrum. The implications of our results to III-Nitride microdisk lasers are discussed.