bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental and Theoretical Study of Structure-Dielectric Property Relationships for Polysilsesquioxanes
Authors: Kim Sung Mog , Yoon Do Y. , Nguyen Cattien V. , Han Jie , Jaffe Richard L. 
Published: April 2011

ABSTRACTStructures of polysilsesquioxanes {(R- SiO1.5)n with R=H, CH3, C6H5} in spin-on thin films are investigated in relation to their dielectric properties. IR spectroscopy in combination with results from quantum chemistry calculations shows that the initial hydrido-silsesquioxane films (cured to 250 °C) exhibit more symmetric ring structures than those for methyl-silsesquioxanes. Moreover, IR spectra indicate that increasing the cure temperature above a critical value, which varies with the Si-R moiety, causes extensive three-dimensional cross-linking in silsesquioxanes via breakage of the Si-R bond and formation of networks of O-Si-O structures with a lower ring symmetry than the initial materials. Dielectric properties do not appear to vary with the structural symmetry about the O-Si-O moiety nor with the R substituents, but rather depend on the extent of three-dimensional cross-linking as seen by the loss of Si-R absorbance. Highly cross-linked silsesquioxanes show a higher dielectric value and no variation with temperature from −100 °C to 150°C range, whereas a lower value and a negative temperature dependence are seen for dielectric constants of silsesquioxane samples with little loss of Si-R absorbance.
5.5 kV Bipolar Diodes From High Quality CVD 411-SiC
Authors: Irvine K. G. , Singh R. , Paisley M. J. , Palmour J. W. , Kordina O. , Carter C. H. 
Published: April 2011

ABSTRACTThick, high quality 4H-SiC material suitable for high power devices has been grown in a hot-wall reactor. Recent improvements to the growth process have improved our thickness uniformity over a 50mm wafer to less than 1% and the doping uniformity to less than 5%, both values expressed as σ/mean.A record breaking reverse blocking voltage of 5.5 kV was obtained on P-i-N diodes fabricated from a 85μm thick film. The on-state voltage drop was 5.4 V at 100 A/cm2. From this on-state voltage drop, the carrier lifetime was estimated in excess of 1μs.
Silicon Carbide Epitaxial Layers Grown ON SiC Wafers With Reduced Micropipe Density
Authors: Rendakova S. , Kuznetsov N. , Savkina N. , Rastegaeva M. , Andreev A. , Minbaeva M. , Morozov A. , Dmitriev V. 
Published: April 2011

ABSTRACTThe characteristics of SiC high-power devices are currently limited by the small area of the devices, which is usually less than 1 sq. mm. In order to increase device area, defect density in SiC epitaxial structures must be reduced. In this paper, we describe properties of silicon carbide epitaxial layers grown on 4H-SiC wafers with reduced micropipe density. These layers were grown by the vacuum sublimation method. Large area Schottky barriers (up to 8 mm2) were fabricated on SiC epitaxial layers and characterized.
Temperature Dependence of Breakdown Field in p-π-n GaN Diodes
Authors: Osinsky A. , Shur M. S. , Gaska R. 
Published: April 2011

ABSTRACTWe present the results of the study of the electric breakdown in p-π-n GaN diodes. The breakdown is observed at reverse biases above 40 V and is accompanied by the formation of microplasmas. The study shows that the observed breakdown field in GaN (on the order of 1 to 2 MV/cm) increases with the temperature. This feature makes GaN very promising for high power devices and avalanche photodetectors, operating at elevated temperatures.
Investigation Of Microplasma Breakdown In 4H Silicon Carbide
Authors: Zimmermann Uwe , Hallén Anders , Konstantinov Andrey O. , Breitholtz Bo 
Published: April 2011

ABSTRACTReverse bias breakdown behaviour of high quality 4H silicon carbide p-n diodes was investigated, using optical and electrical measurement techniques. Most of the sample diodes suffered from early breakdown phenomena in the form of microplasmas at about 80% of the calculated parallel plane breakdown voltage for the diodes, as evident from measured I-V curves. A group of these microplasmas could be correlated to micropipes, identified by optical microscopy, while a large number of microplasmas were caused by other defects and inhomogenities in the space charge region under reverse bias. The same spots that revealed early breakdown phenomena under reverse bias also showed a different electroluminescence (EL) behaviour under low forward current densities compared to those areas with a homogeneous breakdown behaviour. However, even diodes containing one or more micropipes in the region of the junction showed good rectifying behaviour up to two third of the parallel plane breakdown voltage, where the turn-on of a microplasma was observed.
Scandium And Gallium Implantation Doping Of Silicon Carbide
Authors: Henkel T. , Tanaka Y. , Kobayashi N. , Koutzarov I. , Okumura H. , Yoshida S. , Ohshima T. 
Published: April 2011

ABSTRACTRutherford backscattering, Raman spectroscopy as well as photoluminescence, resistivity and Hall measurements have been used to investigate the doping behaviour of Scandium and Gallium ions implanted into Silicon Carbide respectively. The recovery of the crystal lattice after implantation at room temperature followed by rapid thermal annealing is shown to be less effective in the case of Scandium compared with Gallium. Scandium implanted SiC exhibited a high resistivity in comparison to Gallium implanted crystals.
The Magnitude of the Piezoelectric Effect in InGaN Quantum Wells
Authors: Perlin Piotr , Kisielowski Christian , Mattos Laila , Shapiro Noad A. , Kruger Joachim , Yang Jinwei , Weber Eicke R. 
Published: April 2011

ABSTRACTA photoluminescence from a multiquantum GaN/InxGa1−xN/GaN well structure (x varies between 0.1 to 0.4) was investigated at various temperatures, pumping powers. While the temperature dependence of the peak position indicates normal band to band character of radiative recombination, the large pumping power induced “blue”shift of the peak position (up to 200 meV) can be observed. This kind of shift cannot be easily explained by the band tailing effect but is most likely the result of the screening of the strain-induced piezoelectric field. By evaluating the theoretical values of the piezoelectric filelds in the quantum well, we can show that in order to account for the experimental results we have to assume the partial relaxation of the strain.
Role of Nanopipes in Degradation of AlGaN/InGaN/GaN Devices Operating at High Voltage
Authors: Osiński Marek , Lee Jinhyun , Barton Daniel L. 
Published: April 2011

ABSTRACTWe argue that the nanopipes recently observed in device-quality GaN grown on sapphire play an important role in degradation of nitride-based devices requiring high driving voltage, such as diode lasers or high-power electronics. The nanopipes offer a preferential path for the top (p-side) contact metal to migrate down towards the p-n junction under high-voltage operation, eventually causing a short and device failure. The metal migration process is enhanced by high voltage (tens of volts) required to drive high-current pulses through the device, and its elimination is of critical importance for achieving reliable GaN-based power devices and diode lasers.
Nitride Based High Power Devices: Transport Properties, Linear Defects And Goals
Authors: Bandić Z. Z. , Bridger P. M. , Piquette E. C. , Beach R. A. , Phanse V. M. , Vaudo R. P. , Redwing J. , McGill T. C. 
Published: April 2011

ABSTRACTThe wide bandgap semiconductors GaN and AlGaN show promise for high voltage standoff layers in high power devices such as GaN Schottky rectifiers and GaN/AlGaN thyristorlike switches. The material properties which significantly influence the device design and performance are electron and hole diffusion lengths, recombination lifetimes and the critical field for electric breakdown. We have fabricated high standoff voltage (> 450 V) GaN Schot-tky rectifiers, and measured a lower limit for the critical field for electric breakdown to be (2 ± 0.5) · 106 V/cm. Diffusion lengths and recombination lifetimes were measured by electron beam induced current on unintentionally doped, n and p-type GaN samples grown by various epitaxial techniques. To establish the possible effects of linear dislocations and other defects on the transport and breakdown properties, the same sample surfaces were analyzed by AFM. On some of the samples, our measurements indicate that the dislocations appear to be electrically active and that recombination at dislocations occupying grain boundaries limit the minority carrier lifetime to the nanosecond range. Based on the measurements of transport properties, critical fields and the modeling of the devices proposed, our estimates indicate that DARPA/EPRI goals for megawatt electronics set at 5 kV standoff voltage and 200 A on-state current might be achieved with 15 – 20 μm thick layers grown by HVPE, at approximately 1. 1016 cm−3 doping levels, and 1 – 2cm2 device active area.
High Resolution X-ray Diffraction and X-ray Topography Study of Gan on A12O3
Authors: Chaudhuri J. , Ng M. Hooe , Koleske D. D. , Wickenden A. E. , Henry R. L. 
Published: April 2011

ABSTRACTHigh resolution x-ray diffraction and x-ray topography study of GaN thin films, grown on sapphire (00.1) substrate by reduced pressure metalorganic vapor phase epitaxy under various conditions, were performed. An attempt was made to correlate the mobility in films with similar carrier concentration with the strain and dislocation density. X-ray topography revealed the defects present in the film.
Correlation Between Oxide Breakdown And Defects In Sic Wafers
Authors: Soloviev S. , Khlebnikov I. , Madangarli V. , Sudarshan T. S. 
Published: April 2011

ABSTRACTA correlation between gate oxide breakdown in MOS capacitor structures and structural defects in SiC wafers is reported. The oxide breakdown under high applied fields, in the accumulation regime of the MOS capacitor structure, is observed to occur at locations corresponding to the edge of bulk structural defects in the SiC wafer such as polytype inclusions, regions of crystallographic mis-orientation, or different doping concentration. Breakdown measurements on more than 50 different MOS structures did not indicate any failure of the oxide exactly above a micropipe. The scatter in the oxide breakdown field across a 10mm × 10mm square area was about 50%, and the highest breakdown field obtained was close to 8 MV/cm.
Direct Growth of AIN Thin Layer on (111)Si Substrate by RF-MBE
Authors: Ohshima Naoki , Yonezu Hiroo , Uesugi Shinobu , Gotoh Keisuke , Yamahira Seiji 
Published: April 2011

ABSTRACTThe nitridation process of (111)Si surface has been studied by in-situ reflection high-energy electron diffraction (RHEED) and Auger electron spectroscopy (AES) measurements. It has been clarified that the nitridation of the Si surface is occurred even if the shutter of the discharged rf-plasma gun is closed. The growth process of AIN epilayer on the Si substrate by migration enhanced epitaxy (MEE) has been investigated by in-situ RHEED and atomic force microscopy (AFM) observations. It has been found that the AIN epilayer is directly grown on (111)Si by MEE growth.
High Energy Implantation of Boron in 4H-SiC
Authors: Schönerl Adolf , Karlsson Stefan , Schmitt Thomas , Hallén Anders , Frischholz Manfred , Rottner Kurt 
Published: April 2011

ABSTRACTThe high energy implantation of boron into n-type Silicon Carbide epitaxial layers of the polytype 4H was investigated for various sample temperatures during implantation and different doping concentrations. Depth profiling using secondary ion mass spectrometry was applied to determine the boron distribution in the as-implanted epilayers and the re-distribution of boron atoms during a half hour heat treatment at a temperature of 1700 °C. The SIMS boron profiles are compared to numerical Monte Carlo calculations using the program TRIM96 and to electrical profiling by scanning capacitance microscopy.In general we found that boron is moving towards the implantation damage already during the implantation of a profile with four different energies. The defect enhanced diffusion of boron is more pronounced during the high temperature anneal, where a higher concentration of boron diffusing towards the sample surface was observed. Into the bulk of the epilayer the boron diffusion is on a lower level and shows an exponential decay with a length of up to 5 Pm. An out-diffusion of boron during the post implantation anneal was not observed at implantation temperatures up to 500 °C.Electrical profiling using scanning capacitance microscopy revealed that complicated layer structures with several pn-junctions can occur due to the re-distribution of boron during post implantation anneal.
Dry Etching Damage Effect on Ohmic Characteristics of GaN
Authors: Khim Jin Seok , Kim Taek , Chae Su Hee , Kim Tae Il , Kim Hyon-Soo , Yeom Geun-Young 
Published: April 2011

ABSTRACTWe report on the dry etching damage effects on the Ohmic contact characteristics of Sidoped n-type GaN. The 2-µm thick n-type GaN samples whose carrier concentrations are ∼7 × 1017/cm3 are grown on c-plane sapphire substrates by metalorganic chemical vapor deposition(MOCVD). The samples are processed to measure the transmission line method(TLM). We evaporated Ti/Al/Ni/Au=150/2700/400/4000 Å on the samples using an ebeam evaporator under 5 × 10−7 torr and annealed at 700 °C for lminute using a rapid thermal annealer(RTA). AES and XPS data show that the surface stoichiometry of the sample etched with H2 gas is gallium- richer than that of the one etched with Cl2 gas. According to the previous report[l], N-vacancy acts as shallow donor in GaN. However, specific contact resistivity of the sample etched with H2 gas is 3.03 × 10−6 Ω cm 2, which is much higher than that of the sample etched with C12 gas, 7.9 × 10 −7 Ω cm2. The difference of the N- vacancy formed during the etching process cannot completely explain the result. We suggest that formation of GaxOy during etching process, and the weakening of the bonding by ion bombardments might be responsible for the difference in the ohmic characteristics.
Comparison of Novel Chlorine, Bromine and Iodine Plasma Chemistries for Anisotropic Trench Etching In GaN, InN and Ain
Authors: Cho Hyun , Maeda T. , MacKenzie J. D. , Donovan S. M. , Abemathy C. R. , Pearton S. J. , Shul R. J. , Han J. , Ren F. 
Published: April 2011

ABSTRACTAnisotropic pattern transfer has been performed for GaN, InN and AIN in Cl2/Ar, BI3/Ar and BBr3/Ar Inductively Coupled Plasmas(ICP). Controlled etch rates in the range of 500–1500Å·min−1 are obtained for III-nitride materials in Cl2/Ar chemistry. Etch selectivities of 100:1 were achieved for InN over both GaN and AIN in the BI3 mixtures, while for BBr3 discharges values of 100:1 for InN over AIN and 25:1 for InN over GaN were measured.
Low Bias Dry Etching of Sic and Sicn in ICP NF3 Discharges
Authors: Wang J. J. , Cho Hyun , Lambers E. S. , Peartont S. J. , Ostling M. , Zetterling C.-M. , Grow J.M. , Ren F. , Shul R. J. , Han J. 
Published: April 2011

ABSTRACTA parametric study of the etching characteristics of 6H p+ and n+ SiC and thin film SiC0.8N0.2 in Inductively Coupled Plasma NF3/O2 and NF3/Ar discharges has been performed. The etch rates in both chemistries increase monotonically with NF3 percentage and rf chuck power reaching 3500Å·min−1 for SiC and 7500 Å·min−1 for SiCN. The etch rates go through a maximum with increasing ICP source power, which is explained by a trade-off between the increasing ion flux and the decreasing ion energy. The anisotropy of the etched features is also a function of ion flux, ion energy and atomic fluorine neutral concentration. Indium-tinoxide( ITO) masks display relatively good etch selectivity over SiC(maximum of 70:1) while photoresist etches more rapidly than SiC. The surface roughness of SiC is essentially independent of plasma composition for NF3/O2 discharges, while extensive surface degradation occurs for SiCN under high NF3:O2 conditions. The high ion flux available in the ICP tool allows etching even at very low dc self-biases, ≤ −10V, leading to very low damage pattern transfer.
Effect of V/III Ratio on the Properties of GaN Layers Grown by Molecular Beam Epitaxy Using NH3
Authors: Grandjean N. , Leroux M. , Massies J. , Mesrine M. , Lorenzini P. 
Published: April 2011

ABSTRACTAmmonia as nitrogen precursor has been used to grow III-V nitrides by molecular beam epitaxy (MBE) on c-plane sapphire substrates. The efficiency of NH3 has been evaluated allowing the determination of the actual V/III flux ratio used during the GaN growth. The effects of the V/III ratio variation on the GaN layer properties have been investigated by photoluminescence (PL), Hall measurements, atomic force microscopy (AFM), and secondary ion mass spectroscopy (SIMS). It is found that a high V/III ratio leads to the best material quality. Optimized GaN thick buffer layers have been used to grow GaN/AlGaN quantum well (QW) heterostructures. Their PL spectra exhibit well resolved emission peaks for QW thicknesses varying from 3 to 15 monolayers. From the variation of the QW energies as a function of well width, a piezoelectric field of 450 kV/cm is deduced.
Pulsed-Field-Gradient NMR Studies of Hydrogen Diffusion in Laves-Phase Hydrides
Authors: Majer G. 
Published: April 2011

ABSTRACTThe diffusivities D of hydrogen in cubic Laves-phase hydrides have been measured by means of pulsed-field-gradient nuclear magnetic resonance over wide temperature ranges. A review is given of the diffusion coefficients of hydrogen in ZrCr2Hx, rTi2Hx, ZrV2Hx, ZrMo2Hx. and HfV2Hx. with special emphasis on the variation of D with the hydrogen concentration x. The formation of ordered low-temperature phases in ZrV2Hx results in a substantial reduction of the hydrogen diffusivity. The dependence of D on the lattice parameter of the host compound is considered.
Hydrogen Motion In Lanthanum Hydrides By Means Of Quasielastic Neutron Scattering
Authors: Karmonik C. , Udovic T. J. , Rush J. J. 
Published: April 2011

ABSTRACTThe hydrogen dynamics in LaHx was studied for different concentrations x ≥ 2.5 at different temperatures by quasielastic neutron scattering. The neutron spectra show the existence of both long-range translational diffusion and localized motion. The prefactor of the jump rate for the first process exhibits a maximum around x= 2.75. The radius for the second motion is in agreement with neutron powder diffraction measurements which support a localized motion of H confined in an octahedral site.
Hydrogen Migration In Phosphorous Doped Polycrystalline Silicon
Authors: Nickel N. H. , Kaiser I. 
Published: April 2011

ABSTRACTHydrogen diffusion in phosphorous doped polycrystalline silicon was investigated by deuterium diffusion experiments. The presence of phosphorous enhances hydrogen diffusion. For high hydrogen concentrations the activation energy of the effective diffusion-coefficient amounts to 0.25-0.35 eV. At low hydrogen concentrations diffusion is governed by deep traps that are present in an appreciable concentration of 6×108 - 1019 cm−3. The hydrogen chemical-potential, 9H, decreases with increasing temperature at a rate of ˜ 0.002 eV/K. The data are discussed in terms of a two-level model used to describe hydrogen diffusion in amorphous and undoped polycrystalline silicon.
Microscopic Study Of The Hydrogen Diffusion In III-V Semiconductors
Authors: Burchard A. , Deicher M. , Forkel-Wirth D. , Knopf M. , Magerle R. , STötzler A. , Fedoseyev V. N. , Mishin V. I. , Isolde-Collaboration The 
Published: April 2011

ABSTRACTWe report on experiments which observe on a microscopic scale the migration of isolated hydrogen in InP, GaAs, and InAs. Using the radioactive acceptor 117Cd, Cd-H pairs have been formed in these III-V semiconductors. After the decay of 117Cd to 117In, H is no longer bound to an acceptor and can diffuse freely. This diffusion has been observed by perturbed yy angular correlation (PAC) spectroscopy. At 10 K, the occupation of two different lattice sites by hydrogen has been observed. First results on the diffusion of hydrogen will be discussed.
Annealing Behavior of the Hydrogen-Vacancy Complex in Bulk Indium Phosphide Crystals
Authors: Ye Q. , Wolk J. A. , Bourret-Courchesne E. D. , Bliss D. F. 
Published: April 2011

ABSTRACTIn order to explain the effects of hydrogen on the electrical properties of bulk indium phosphide crystals, we have performed a series of high temperature annealing studies with both undoped and iron-doped indium phosphide crystals. Our samples were annealed at 900°C for 6, 36, and 72 hours, respectively, under a phosphorus overpressure of five atmospheres. Samples were characterized at 10 K by Fourier transform infrared absorption spectroscopy which allowed us to measure the concentrations of both the Fe2+ and VIn-H4 defects simultaneously. Undoped samples were further characterized by the Hall effect measurements. We find in the iron-doped samples that the [Fe2+]/[Fe3+] ratio decreases gradually with increasing annealing time, indicating a reduction in the number of donors in the samples. In the undoped samples, annealing leads to a reduction of the free electron concentration accompanied by an increase in the 77 K mobility. The increase of the sample's mobility eliminates the possibility that the reduction of the free electron concentration is due to an increase in the concentration of the compensating acceptors. Our explanation for the observed behavior in all samples is that hydrogen acts as a donor and it diffuses out of the crystal during the annealing process. Based on our experimental data, we propose a calibration equation of [VIn-H4] = 4.2×1016 cm−1 × Absorbance (cm−1) which is used to correlate the hydrogen-vacancy complex concentrations with the changes of the VIn-H4 absorption peak in both the iron-doped and the undoped samples. Our results confirm the donor nature of the hydrogen-vacancy complex and provide strong evidence regarding the reduction mechanism of free carrier concentrations in bulk indium phosphide crystals during high temperature annealing under a phosphorus atmosphere.
An Alternative Approach for Modeling the Hot Carrier Degradation of the Si/SiO2 Interface
Authors: Chen Zhi , Lee Jinju , Lyding Joseph W. 
Published: April 2011

ABSTRACTAn alternative approach for modeling the hot carrier degradation of the Si/SiO2 interface based on the dispersive characteristics of the interface trap generation has been proposed. The timedependent interface trap generation has been modeled using the stretched exponential expression. The conventional power law of degradation is just the approximation of this general form. Very good agreement has been found between the theoretical model and the experimental data. This approach gives more physical insight into the understanding of the mechanism for the interface trap generation.
Deuterium Diffusion, Trapping and Stability in Buried Silicon Dioxide Layers
Authors: Boutry-Forveille A. , Nazarov A. , Ballutaud D. 
Published: April 2011

ABSTRACTThe interaction of hydrogen (deuterium used as tracer) with Si-Si02-Si buried oxide layers (BOX) prepared by thermal oxidation or by oxygen implantation (SIMOX) are investigated using Secondary Ion Mass Spectrometry (SIMS) measurements combined with effusion experiments. The sample deuteration is performed at different temperatures between 150 and 300°C using a radiofrequency plasma. In SIMOX samples, the deuterium diffusion profiles analysed by SIMS show deuterium trapping on implantation defects, and deuterium diffusion in the silicon substrate by permeation through the oxide layer for temperatures higher than 250°C. The deuterium is still detected in the buried oxide layers after isothermal annealing at 600°C during 2 hours. The deuterium trapping at the siliconsilicon dioxide interfaces is analysed.