bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of Indium Surfactant on the Optoelectronic and Structural Properties of MBE Grown Gallium Nitride
Authors: Zhu C.F. , Fong W.K. , Leung B.H. , Cheng C.C. , Surya C. , Sundaravel B. , Luo E.Z. , Xu J.B. , Wilson I.H. 
Published: April 2011

ABSTRACTGallium nitride films were grown by rf-plasma assisted molecular beam epitaxy. A small indium flux was used as surfactant during the growth. The optical and electrical properties of the films grown with and without In surfactant were characterized by investigating the photoluminescence (PL), high resolution x-ray diffraction (HRXRD) and low-frequency noise power spectra. The sample grown in the presence of In surfactant showed a suppressed yellow luminescence (YL) compared to the one grown without In surfactant. Significant reduction in the full width at half maximum of the GaN (0002) x-ray diffraction peak, indicating a better film quality, was obtained when In surfactant was used during growth. Atomic force microscopy studies show that the root mean squared surface roughness for films grown with and without the In surfactant are 5.86 and 6.99 nm respectively indicating significant improvement in surface morphology. This is attributed to the enhanced 2-dimensional growth by In surfactant. A smaller Hooge parameter was obtained from the low-frequency noise measurement for the sample grown with In surfactant indicating that application of In surfactant led to significant reduction in the trap density of the material.
Real-Time Pseudodielectric Function of Low-Temperature-Grown GaAs
Authors: Gajewski D.A. , Guyer J.E. , Kopanski J.J. , Pellegrino J.G. 
Published: April 2011

ABSTRACTWe present the real-time pseudodielectric function <ε(E)> of low-temperature-grown GaAs (LT-GaAs) thin films during the growth as a function of growth temperature Tg and thickness. We obtained accurate measurements of the real-time <εc(E)> by using in situspectroscopic ellipsometry (SE) in conjunction with active feedback control of the substrate temperature using diffuse reflectance spectroscopy. We show that for epitaxial LT-GaAs layers, the peak in the imaginary pseudodielectric function <ε2(E)> decreases in amplitude and sharpness systematically with decreasing Tg. We also revealed an abrupt change in <εc(E)> near the critical epitaxial thickness hepi, the value of which decreases with decreasing Tg. Above hepi, the LT-GaAs grows polycrystalline (amorphous) above (below) Tg ∼ 190°C. We also simultaneously monitored the surface roughness and crystallinity by using real-time reflection high-energy electron diffraction (RHEED). These results represent progress in obtaining real-time control over the composition and morphology of LT-GaAs
Determine the Three-Dimensional Crystallographic Misorientation in Heterostructures by Selected Area Diffraction (SAD) in TEM
Authors: Guo X. J. , Wen C.-Y. , Huang J. H. , Shih H. C. 
Published: April 2011

ABSTRACTWe proposed a concise and novel scheme to determine the crystallographic misorientation of heteroepitaxial structures. In addition to subtle high-resolution transmission electron microscope images, the information revealed from selected-area diffraction patterns at the interfaces offers another path to determine the angles of misorientations. The principle is to extract the basically three-dimensional misorientation information from a two-dimensional selected-area diffraction pattern through the employment of the Laue circle
Highly Ordered Uniform Quantum Dots Induced by Ion Sputtering
Authors: Kurz H. , Facsko S. , Bobek T. , Dekorsy T. 
Published: April 2011

ABSTRACTSelf-organized hexagonally ordered quantum dot patterns are produced on GaSh (100) and InSb (100) surfaces by low energy Ar+-ion sputtering at normal angle of incidence. The QDs are crystalline, exhibiting narrow size distributions with diameters from 17–80 nm depending on sputter conditions, densely packed with densities as high as 2 × 1011 cm−2. The origin of the QD formation is attributed to the interplay of two surface processes during ion bombardment: ion induced surface roughening, provoked by the curvature dependent sputter yield and balanced by surface diffusive processes. The observed QD patterns obtained at different sputter conditions show that the formation mechanism can be described by the Kuramoto-Sivashinsky equation. The dominant diffusive process emerges to be effective ion induced without any mass transport on the surface, inherent to the sputtering process.
Formation of Gallium Nitride (GaN) Transition Layer by Plasma Immersion Ion Implantation and Rapid Thermal Annealing
Authors: Kwok D. T. K. , Ho A. H. P. , Zeng X. C. , Chan C. , Chu P. K. , Wong S. P. 
Published: April 2011

ABSTRACTRecent advances in the preparation of gallium nitride (GaN) and related compounds have made possible the production of blue semiconductor laser. Conventional preparation involves growing GaN thin films on lattice-mismatching sapphire using metal-organic chemical vapor deposition (MOCVD). In this article, we describe an alternative method to produce a lattice-matching strained layer in GaAs for subsequent GaN growth by plasma immersion ion implantation (PIII) followed by rapid thermal annealing. Our novel approach uses broad ion impact energy distribution and multiple implant voltages to form a spread-out nitrogen depth profile and an amorphous surface layer. This approach circumvents the retained dose and low nitrogen content problems associated with ion beam implantation at fix energy. Based on our Raman study, the resulting structure after PIII and rapid thermal annealing is strained and contains some GaN possibly in crystal form
Epitaxial Growth of Co3O4 Films by Low Temperature, Low Pressure Chemical Vapor Deposition
Authors: Shalini K. , Mane Anil U. , Lakshmi R. , Shivashankar S.A. , Rajeswari M. , Choopun S. 
Published: April 2011

ABSTRACTThe growth of strongly oriented or epitaxial thin films of metal oxides generally requires relatively high growth temperatures or infusion of energy to the growth surface through means such as ion bombardment. We have grown high quality epitaxial thin films of Co3O4 on different substrates at a temperature as low as 450°C by low-pressure metal-organic chemical vapor deposition (MOCVD) using cobalt(II) acetylacetonate as the precursor. With oxygen as the reactant gas, polycrystalline Co3O4 films are formed on glass and Si(100) in the temperature range 350-550°C. Under similar conditions of growth, highly oriented films of Co3O4 are formed on SrTiO3(100) and LaAlO3(100). The film on LaAlO3(100) grown at 450°C show a rocking curve FWHM of 1.61°, which reduces to 1.32° when it is annealed in oxygen at 725°C. The film on SrTiO3(100) has a FWHM of 0.330 (as deposited) and 0.29° (after annealing at 725°C). The ø-scan analysis shows cube-on-cube epitaxy on both these substrates. The quality of epitaxy on SrTiO3(100) is comparable to the best of the pervoskite-based oxide thin films grown at significantly higher temperatures.
Structure Characterization of Epitaxial Strain Relaxation in YBa2Cu3O7−x/PrBa2Cu3O7 Superlattices
Authors: Varela María , Arias Diego , Sefrioui Zouhair , León Carlos , Ballesteros Carmen , Santamaría Jacobo 
Published: April 2011

ABSTRACTThe structure of c-axis oriented [YBa2Cu3O7−(YBCO) N / PrBa2Cu3O7 (PBCO)M/1000Å superlattices with N ranging between 1 and 12 and M=5 unit cells, grown by high oxygen pressure sputtering on (100) SrTiO3 substrates, is analyzed by x-ray diffraction (XRD) and highresolution transmission electron microscopy (HREM). The XRD spectra refinement shows epitaxial strain for YBCO thickness below 4 unit cells. For larger YBCO layer thickness, stress relaxes and step disorder builds up. HREM observations show sharp and flat interfaces between substrate and superlattice stack. The only observable defects are isolated steps or a-axis oriented domains in relaxed samples. The results of both structural tools are compared.
Epitaxial Growth of Cerium Oxide Buffer Layers on MgO, YSZ and Sapphire Substrates
Authors: Thorley A. , Gnanarajan S. , Katsaros A. , Savvides N. 
Published: April 2011

ABSTRACTWe studied the epitaxial growth of CeO2 thin films deposited onto MgO(100), YSZ(100) and Al2O3(1102 ) (r-plane sapphire) substrates by reactive dc magnetron sputtering of a Ce metal target in an Ar/O2 plasma. The crystalline quality and biaxial alignment of the films was determined using x-ray diffraction techniques (θ-2θ, ω-scans, pole figures, ø-scans). The CeO2/MgO(100) and CeO2/Al2O3(1102) epitaxy was evident at 600°C and developed to nearly perfect biaxial alignment at 850°C with Δø = 5° and 9° respectively. The CeO2/YSZ (100) epitaxy occurred below 300°C while deposition at ≥ 650°C led to single-crystal quality CeO2 films with Δø = 0.2°.
Observation of a New Ordered Structure of Oxygen on W(110)
Authors: Muzzall D. E. , Chiang S. 
Published: April 2011

ABSTRACTUsing both low energy electron diffraction (LEED) and scanning tunneling microscopy (STM), we have made the first observation of a new ordered surface structure of oxygen on W(110). This structure is characterized by the matrix relative to the (1×1) W(110) structure, in which 15 tungsten atoms make up the rectangular unit cell. Based on high resolution STM images, a model for the structure is proposed which includes 6 adsorbed oxygen atoms and has a coverage of 0.40 ML.
A Novel Method for True Work Function Determination of Metal Surfaces by Combined Kelvin Probe and Photoelectric Effect Measurements
Authors: Lägel Bert , Baikie Iain D. , Dirscherl Konrad , Petermann Uwe 
Published: April 2011

ABSTRACTWe have developed a novel method for in-situ measurements of the true work function (ø) of metal surfaces by combined ultra-high vacuum compatible Kelvin Probe and photoelectric effect measurements. The work function is an extremely sensitive parameter of surface condition and can be used to study oxidation and thin film growth on metal surfaces. For example, the increase in ø due to oxidation of polycrystalline rhenium is 1.9eV.The Kelvin Probe measures local work function differences between a conducting sample and a reference tip in a non-contact, truly non-invasive way over a wide temperature range. However, it is an inherently relative technique and does not provide an absolute work function if the work function of the tip (øtip) is unknown.We present a novel approach to measure øtip with the Kelvin Probe via the photoelectric effect, using a Gd foil as the photoelectron source, hereby combining the advantages of both methods to provide the absolute work function of the sample surface. We demonstrate the application of the technique by in-situ work function measurements during oxidation of polycrystalline rhenium. The extended Kelvin Probe method therefore has potential applications as a characterisation tool for thin film epitaxy and work function engineering of surfaces.
Isothermal I-V Characteristics of 4H-SiC p-n Diodes with Low Series Differential Resistivity at Avalanche Breakdown
Authors: Vassilevski Konstantin V. , Zekentes Konstantinos , Zorenko Alexandr V. , Romanov Leonid P. 
Published: April 2011

ABSTRACT4H-SiC p+-n-n+ diodes of low series resistivity were fabricated and packaged. The diodes exhibited a homogeneous avalanche breakdown at voltage Ub=260V. These diodes were capable to dissipate a pulsed power density of 7.4 MW/cm2 at avalanche current. Isothermal I-V characteristics of fabricated diodes were measured at forward bias and at avalanche breakdown. An experimental determination of the electron saturated drift velocity along the c-axis in 4H-SiC was performed for the first time. It was found to be 7.7×106cm/s at room temperature.
Temperature Dependence and Current Transport Mechanisms in AlxGa1−xN Schottky Rectifiers
Authors: Zhang A.P. , Cao X.A. , Dang G. , Ren F. , Han J. , Chyi J.-I. , Lee C.-M. , Chuo C.-C. , Nee T.E. 
Published: April 2011

ABSTRACTGaN and Al0.25Ga0.75N lateral Schottky rectifiers were fabricated either with (GaN) or without (AlGaN) edge termination. The reverse breakdown voltage VB (3.1 kV for GaN with both p+ guard rings and metal overlap edge terminations; 4.3 kV for Al0.25Ga0.75N without edge termination) displayed a negative temperature coefficient of −6.0 ± 0.4 V·K−1 for both types of rectifiers. The reverse current originated from contact periphery leakage at moderate bias, while the forward turn-on voltage at a current density of 100A·Cm−2 was ∼5 V for GaN and ∼7.5 V for AlGaN. The on-state resistances, RON, were 0.13 Δcm2 for GaN and 2.3 Δcm2 for AlGaN, producing figures-or-merit (VRB)2/RON of 73.9 and 8.2 MW.Cm−2, respectively. The activation energy of the reverse leakage was 0.13 eV at moderate bias.
Design and Performance of Nitride-based UV LEDs
Authors: Crawford M. H. , Han J. , Shul R. J. , Banas M. A. , Figiel J. J. , Zhang L. 
Published: April 2011

ABSTRACTWe overview several of the challenges in achieving high efficiency nitride-based UV (< 400 nm) LEDs. The issue of optical efficiency is presented through temperature-dependent photoluminescence studies of various UV active regions. These studies demonstrate enhanced optical efficiencies for active regions with In-containing alloys ( InGaN, AlInGaN). We compare the performance of two distinct UV LED structures. GaN/AlGaN quantum well LEDs with λ < 360 nm emission have demonstrated output powers > 0.1 mW, but present designs suffer from internal absorption effects. InGaN/AlInGaN quantum well LEDs with 370 nm< λ < 390 nm emission and > 1 mW output power are also presented.
DLTS study of 3C-SiC grown on Si using hexamethyldisilane
Authors: Kato M. , Ichimura M. , Arai E. , Masuda Y. , Chen Y. , Nishino S. , Tokuda Y. 
Published: April 2011

ABSTRACTn-type 3C-SiC was heteroepitaxially grown on n-type Si(100) substrates using HMDS (hexamethyldisilane) and characterized by DLTS (deep level transient spectroscopy) measurements. In order to investigate relationship of defect density with epilayer thickness, epilayers with various thicknesses were grown. Relatively thin (<1.0μm thick) epilayers were found to contain defects with energy levels distributed in a wide energy range, while relatively thick (>2.2μm thick) epilayers contain a defect with an activation energy of 0.25eV. This defect level is slightly shallower than that in 3C-SiC grown by SiH4 and C3H8 (∼0.3eV).
Non-Contact Characterization of Recombination Processes in 4H-SiC
Authors: Matocha K. , Chow T.P. , Gutmann R.J. 
Published: April 2011

ABSTRACTCarrier decay transients in 4H-SiC n-type and p-type epilayers have been charac-terized using a non-destructive, non-contact microwave photoconductivity technique. Decay transients show a two-stage exponential decay with first decay constants as high as 400 ns in 10 νm p-type epilayers. The second decay constant increases with temperature and is dominated by interface recombination.
Lateral and Vertical Growth Study in the Initial Stages of GaN Growth on Sapphire with ZnO Buffer Layers by Hydride Vapor Phase Epitaxy
Authors: Gu Shulin , Zhang Rong , Zhang Ling , Kuech T. F. 
Published: April 2011

ABSTRACTThe initial stage of hydride vapor phase epitaxy GaN growth on ZnO-buffered sapphire is reported. A high supersaturation in the growth ambient was used to favor a rapid initial growth on the substrate. A subsequent step with high lateral growth rate was chosen to promote coalescence of the initial islands and provide optimal material properties. The specific mole fractions of the GaCl and NH3 control these vertical and lateral growth rates. The use of a two- step growth process in the GaN growth has led to improved and controlled morphology and high quality GaN materials have then been grown on sapphire substrate with and without ZnO buffer layers.
Achievements and Characterizations of GaN With Ga-Polarity in Radio-Frequency Plasma-Assisted Molecular Beam Epitaxy
Authors: Shen X.Q. , Ide T. , Cho S.H. , Shimizu M. , Hara S. , Okumura H. 
Published: April 2011

ABSTRACTLattice polarities and film qualities of GaN grown by rf-MBE were investigated concentrating on the use of different buffer layer processes at the initial stage. Direct clarifying by coaxial impact collision ion scattering spectra technique, together with RHEED and chemical wet etching, were applied to identify the lattice polarity of GaN films. XRD rocking curve and photoluminescence results showed that the qualities of GaN films with Ga-polarity were dramatic improved compared to those with N-polarity. Hall effect measurement results indicated that the mobility of the Ga-face film was increased to one order higher (568 cm2/Vs in maximum at room temperature) than that of N-face one.
Short gate length AlGaN/GaN HEMTs
Authors: Breitschädel O. , Kley L. , Gräbeldinger H. , Kuhn B. , Scholz F. , Schweizer H. 
Published: April 2011

ABSTRACTWe report on our progress on the fabrication of AlGaN/GaN HEMTs with extremely short gate length. AlGaN/GaN HEMTs with different gate length from 6 νm down to 60nm were fabricated to investigate DC- and high frequency behavior as well as short channel effects. We have found that the transistors with gates in the 100 nm range can be improved in the device performance with respect to transconductance and high frequency but shows also short channel effects as the loss of saturation in the output characteristics and a strong dependency of the threshold voltage on the gate length.
Pendeo Epitaxy Of 3C-SiC on Si Substrates
Authors: Carter G.E. , Zheleva T. , Melnychuck G. , Geil B. , Jones K. , Saddow S. E. 
Published: April 2011

ABSTRACTPendeo Epitaxy is a type of Lateral Epitaxial Overgrowth (LEO) that instead of using a dielectric buffer layer, uses an etched substrate to grow laterally without an interface layer. We report the first successful growth of 3C-SiC on Si using Pendeo epitaxy. Rectangular stripes of 3C-SiC on (100) Si substrates were fabricated, along both the [110] and [100] directions. Pendeo epi was only observed for columns parallel to [001], indicating a preferred growth facet for Pendeo epi of 3C-SiC on Si. SEM and TEM investigations were performed to assess the material quality of the Pendeo 3C-SiC material. Films were grown for 60 min at 1310°C and film coalescence was achieved without evidence of voids where the growth fronts joined. TEM data indicate not only the growth of vertical and lateral 3C-SiC on the 3C-SiC seed layer but direct nucleation of 3C-SiC on the exposed Si columns side wall and trench bottom, despite the lack of a carbonization procedure. The quality of the Pendeo 3C-SiC film appears to be of high quality indicating that Pendeo epi of 3C-SiC on low-cost, large-diameter Si substrates may prove to be a cost effective way to grow device-grade SiC layers on Si substrates for device applications.
Microstructure and Thermal Stability of Transition Metal Nitrides and Borides on GaN
Authors: Jasiński Jacek , Kamińska Eliana , Piotrowska Anna , Barcz Adam , Zieliński Marcin 
Published: April 2011

ABSTRACTMicrostructure and thermal stability of ZrN/ZrB2 bilayer deposited on GaN have been studied using transmission electron microscopy methods (TEM) and secondary ion mass spectrometry (SIMS). It has been demonstrated that annealing of the contact structure at 1100°C in N2 atmosphere does not lead to any observable metal/semiconductor interaction. In contrast, a failure of the integrity of ZrN/ZrB2 metallization at 800°C, when the heat treatment is performed in O2 ambient has been observed.
Hall effect measurements at low temperature of arsenic implanted into 4H-silicon carbide
Authors: Senzaki J. , Fukuda K. , Ishida Y. , Tanaka Y. , Tanoue H. , Kobayashi N. , Tanaka T. , Arai K. 
Published: April 2011

ABSTRACTThe arsenic dose dependence of electrical properties for implanted samples at 500°C and subsequently annealed at 1600°C for 30min has been investigated to derivate the activation energies of the arsenic donors in silicon carbide. Hall effect measurements were performed between 20K and 773K. Hall carrier concentration of implanted sample with high dose of 7×1015 cm−2 is independence of temperature, which indicates the formation of implanted layer with metallic conduction. For the sample with low dose of 1×1014 cm−2, the experimental Hall mobility varies directly as T3/2 below 80K and as T−3/2 above 150K. The activation energies of arsenic donors determined from the implanted sample with low dose using a least-squares fit of the charge neutrality equation are 66.8 meV for hexagonal site and 127.0 meV for cubic site, respectively.
Hydrothermal Preparation of Ba(Ti,Zr)O3 Thin Films From Ti-Zr Metallic Alloys on Silicon Substrate
Authors: Xia Chang-Tai , Fuenzalida V. M. , Zarate R. A. 
Published: April 2011

AbstractBa(Ti,Zr)O3 thin films were grown hydrothermally on silicon substrates coated with sputtered a Ti-34 at.%Zr metallic alloy thin film. To ensure the formation of Ba(Ti,Zr)O3 under the hydrothermal conditions at 150°C, the concentration of the Ba(OH)2 had to be greater than 0.25 M. Preliminary capacitance measurement revealed a dielectric constant of 200 in Ba(Ti,Zr)O3 films of approximately 320 nm. The formation mechanism is discussed.
Transparent p- and n-Type Conductive Oxides With Delafossite Structure
Authors: Yanagi Hiroshi , Ueda Kazushige , Ibuki Shuntaro , Hase Tomomi , Hosono Hideo , Kawazoe Hiroshi 
Published: April 2011

AbstractThin films of CuAlO2, CuGaO2 and AglnO2 with delafossite structure were prepared on sapphire substrates by pulsed laser deposition method. The resulting CuA102 thin films exhibited p-type conduction and the electrical conductivity at room temperature was 0.3 Scm−1. CuGaO2 thin films were grown epitaxially on μ-Al2O3 (001) surface and showed p-type conduction (conductivity at room temperature = 0.06 S cm−1). The optical band gap was estimated to be ∼3.5 eV for CuAlO2 or ∼3.6 eV for CuGaO2. On the other hand, the thin film of Sn doped AglnO2 exhibited n-type conduction. The optical band gap and electrical conductivity at room temperature were ∼4.1 eV and 70 S cm−1, respectively. The recent work demonstrates the validity of our chemical design concept for p- and n-type transparent conducting oxides, providing an opportunity for realization of transparent p-n junction using delafossite-type oxides.
Buried Oxide Channel Field Effect Transistor
Authors: Misewich J.A. , Schrott A.G. 
Published: April 2011

AbstractA room temperature oxide channel field effect transistor with the channel on the surface was recently demonstrated at IBM which showed switching characteristics similar to conventional silicon FETs. In this paper we introduce a new architecture for the oxide channel transistor where the oxide channel material is buried below the gate oxide layer. This buried channel architecture has several significant advantages over the surface channel design in coupling capacitance, channel mobility, and channel stability. We will discuss the design and fabrication of the buried channel oxide FET and we will present results from these devices which demonstrate a higher transconductance.