bluuebunny/crossref_metadata_2025_split huggingface dataset:
Long Time-Constant Trap Effects in Nitride Heterostructure Field Effect Transistors
Authors: Dang Xiaozhong , Asbeck Peter M. , Yu Edward T. , Boutros Karim S. , Redwing Joan M. 
Published: April 2011

ABSTRACTCurrent collapse effects in an Al0.25Ga0.75N/GaN HFET have been investigated under pulsed bias conditions, and a detailed investigation of current responses to changes in drain or gate bias voltage (drain-lag and gate-lag, respectively) has been performed. Three components of transient current response to changes in drain and gate bias voltages are distinguished. Surface treatment using KOH etching and the influence of pulsed bias conditions on threshold voltage are investigated to explore the origins of traps associated with each current transient component.
Lattice Parameters and Thermal Expansion of Important Semiconductors and Their Substrates
Authors: Reeber Robert R. , Wang Kai 
Published: April 2011

ABSTRACTThermal expansion and lattice parameters are useful thermophysical properties of materials. A knowledge of their temperature dependence is essential for optimizing device design and crystal growth conditions while minimizing the residual stress in epitaxial films and electronic devices. Currently first principles theory can predict lattice parameters to 0.01%. Information required for device design and thin film crystal growth requires improvements two to three orders of magnitude better than this. Available experimental results from our work and the literature will be reviewed in terms of a high temperature predictive model. Tables of thermal expansion and lattice parameters for AlN, GaN, 6H-SiC, β-SiC, MgO, Al2O3, ZnO and GaAs are provided.
Electric and Morphology Studies of Ohmic Contacts on AlGaN/GaN
Authors: Tilak V. , Dimitrov R. , Murphy M. , Green B. , Smart J. , Schaff W.J. , Shealy J.R. , Eastman L.F. 
Published: April 2011

ABSTRACTAlGaN/GaN is a promising system for high power electron devices. Quality of ohmic contacts is a critical parameter in determining the performance of the device. Although we have achieved a transfer resistance (Rc) of 0.35Δmm and ρc of 9.5×10−7 Δcm−2 the morphology and edge acuity of the contacts are poor. The standard ohmic contact recipes consist of a combination of Titanium and Aluminum with Nickel and/or Gold. This is annealed at 800°C-950°C [1-5]. In this work we study ohmic contacts on unintentionally doped Al0.3Ga0.7N/GaN system. We look at ratios of Ti/Al from 0 to 2 to determine which is the optimum ratio in terms of surface morphology and electrical characteristics. From our studies we conclude that morphology of a Ti/Al contact is good over a ratio of 0.3 and the contact resistance is minimized at a Ti/Al of 0.6. The ohmic contacts are improved electrically if a layer of gold is added on top. The best electrical contacts however were obtained with a four layer recipe of Ti/Al/Ti/Au, which gave contact resistance (Rc) around 0.45Δmm, but the morphology of the contacts was poor.
Inductively Coupled High-Density Plasma-Induced Etch Damage of GaN MESFETs
Authors: Shul R. J. , Zhang L. , Baca A. G. , Willison C. G. , Han J. , Pearton S. J. , Lee K. P. , Ren F. 
Published: April 2011

ABSTRACTThe fabrication of a wide variety of GaN-based photonic and electronic devices depends on dry etching, which typically requires ion-assisted removal of the substrate material. Under conditions of both high plasma flux and energetic ion bombardment, GaN etch rates greater than 0.5 νm/min and anisotropic etch profiles are readily achieved in Inductively Coupled Plasma (ICP) etch systems. Unfortunately, under these conditions plasma-induced damage often occurs. Attempts to minimize such damage by reducing the ion energy or increasing the chemical activity in the plasma often result in a loss of etch rate or profile control which can limit dimensional control and reduce the utility of the process for device applications requiring anisotropic etch profiles. It is therefore necessary to develop plasma etch processes which couple anisotropy for critical dimension and sidewall profile control and high etch rates with low-damage for optimum device performance. In this study we report changes in source resistance, reverse breakdown voltage, transconductance, and drain saturation current for GaN MESFET structures exposed to an Ar ICP plasma. In general, device performance was sensitive to ion bombardment energy and ion flux.
Silicon Carbide Die Attach Scheme for 500°C Operation
Authors: Chen Liang-Yu , Hunter Gary W. , Neudeck Philip G. 
Published: April 2011

ABSTRACTSingle crystal silicon carbide (SiC) has such excellent physical, chemical, and electronic properties that SiC based semiconductor electronics can operate at temperatures in excess of 600°C well beyond the high temperature limit for Si based semiconductor devices. SiC semiconductor devices have been demonstrated to be operable at temperatures as high as 600°C, but only in a probe-station environment partially because suitable packaging technology for high temperature (500°C and beyond) devices is still in development. One of the core technologies necessary for high temperature electronic packaging is semiconductor die-attach with low and stable electrical resistance. This paper discusses a low resistance die-attach method and the results of testing carried out at both room temperature and 500°C in air. A 1 mm2 SiC Schottky diode die was attached to aluminum nitride (AlN) and 96% pure alumina ceramic substrates using precious metal based thick-film material. The attached test die using this scheme survived both electronically and mechanically performance and stability tests at 500°C in oxidizing environment of air for 550 hours. The upper limit of electrical resistance of the die-attach interface estimated by forward I-V curves of an attached diode before and during heat treatment indicated stable and low attach-resistance at both room-temperature and 500°C over the entire 550 hours test period. The future durability tests are also discussed.
The Effects of Post-Oxidation Anneal Conditions on Interface State Density Near the Conduction Band Edge and Inversion Channel Mobility for SiC MOSFETs
Authors: Chung G.Y. , Tin C.C. , Williams J. R. , McDonald K. , Ventra M. Di , Pantelides S.T. , Feldman L.C. , Weller R.A. 
Published: April 2011

ABSTRACTResults are reported for the passivation of interface states near the conduction band edge in n-4H-SiC using post-oxidation anneals in nitric oxide, ammonia and forming gas (N2/5%H2). Anneals in nitric oxide and ammonia reduce the interface state density significantly, while forming gas anneals are largely ineffective. Results suggest that interface states in SiO2/SiC and SiO2/Si have different origins, and a model is described for interface state passivation by nitrogen in the SiO2/SiC system. The inversion channel mobility of 4H-SiC MOSFETs increases with the NO annealing.
Deep RIE Process for Silicon Carbide Power Electronics and MEMS
Authors: Beheim Glenn , Salupo Carl S. 
Published: April 2011

ABSTRACTReactive ion etching (RIE) of silicon carbide (SiC) to depths ranging from 10 μm to more than 100 μm is required for the fabrication of SiC power electronics and SiC MEMS. A deep RIE process using an inductively coupled plasma (ICP) etch system has been developed which provides anisotropic etch profiles and smooth etched surfaces, a high rate (3000 Å/min), and a high selectivity (80:1) to the etch mask. An etch depth of 100 μm is demonstrated.
Pyroelectric Coefficient Optimization Through Grain Size Control in (Ba, Sr)TiO3 Thin Films
Authors: Schloss Lawrence F. , Haller Eugene E. 
Published: April 2011

AbstractThin Ba0.2Sr0.8TiO3 films were pulsed laser deposited at laser pulse repetition rates of 1, 5 and 20 Hz in order to assess the effect of grain size on pyroelectric properties. Scanning electron microscopy reveals an increase in columnar grain size with decreasing laser pulse rate, as expected. Substrate bending measurements show an increase in tensile stress with increasing grain size, suggesting some form of stress relaxation has occurred. X-ray diffraction studies reveal all films to be epitaxial and oriented, while Rutherford Backscattering Spectroscopy finds no significant differences in film composition. The films grown at 5 and 20 Hz display a suppressed dielectric permittivity as a function of temperature, while the film deposited at 1 Hz displays an unusually sharp and large dielectric permittivity peak. A variation on current theory concerning phase transitions of stressed ferroelectric thin films is proposed to explain these results.
Control of Valence States in ZnO by CoDoping Method
Authors: Yamamoto T. , Yoshida H. -K. 
Published: April 2011

AbstractWe have investigated the electronic structures of p- or n-type doped ZnO based on ab initio electronic band structure calculations in order to control valence states in ZnO for the fabrication of low-resistivity p-type ZnO. We find unipolarity in ZnO; p-type doping using Li or N increases the Madelung energy while n-type doping using Al, Ga, In or F species decreases the Madelung energy. We have proposed materials design: codoping using N acceptors and reactive codopants, Al or Ga, enhances electric properties in p-type codoped ZnO. It has been already verified by experiments using the N acceptors and Ga reactive donor codopants. We find a very weak repulsive interaction between Li acceptors and the delocalization of the Li-impurity states for Lidoped ZnO, in contrast with the case of N-doped ZnO. On the other hand, we find the compensation mechanism by the formation of 0 vacancy in the vicinity of the Li-acceptor sites. We propose a group VII element, F species, as a promising candidate for use of the reactive codopant as for Li-doped ZnO in order to realize low-resistivity p-type ZnO.
A Study of the Crystallization of Amorphous Indium (Tin) Oxide
Authors: Paine David C. , Chason Eric , Chen Eric , Sparacin Dan , Yeorn Hyo-Young 
Published: April 2011

AbstractThe crystallization of amorphous indium oxide thin films with zero to 9.8 wt% SnO2, was studied using a combination of in situ MOSS (multibeam optical stress senor) and in situ resistivity measurements. We report that amorphous indium oxide deposited using electron beam evaporation undergoes crystallization in a two part process of amorphous structure relaxation followed by crystallization. MOSS measurements show that the relaxation process corresponds to a densification of the amorphous structure while crystallization results in a molar volume increase.
Low Electrically Resistive Transparent Indium-Tin-Oxide Epitaxial Film on (001) Surface of YSZ by Pulsed Laser Deposition
Authors: Ohta Hiromichi , Orita Masahiro , Hirano Masahiro , Hosono Hideo , Kawazoe Hiroshi , Tanji Hiroaki 
Published: April 2011

AbstractHigh quality ITO thin films were grown hetero-epitaxially on extremely flat substrate of (001) YSZ by a pulsed laser deposition technique at a substrate temperature of 600°C. The crystal orientation relationship between the film and YSZ were confirmed as ITO (001) // YSZ (001) and ITO (010) // YSZ (010), respectively, by HR-XRD and HR-TEM. The carrier densities of the films were almost equal to Sn02 concentration in the films. That is, almost all the doped Sn4+ ions were activated to release electrons to the conduction band. The carrier densities of the films were enhanced up to 1.9×1021cm−3, while the Hall mobility showed a slight, almost linear, decrease from 55 to 40cm2V−1s−1 with increasing SnO2 concentration. The low resistivity is due to larger electron mobility, which most likely resulted from good crystal quality of the films. The optical transmissivity of the film exceeded 85% at wavelengths from 340 to 780nm.
Room Temperature Operation of UV-LED Composed of TCO Hetero p-n Junction, p-SrCu2O2/n-ZnO
Authors: Ohta Hiromichi , Kawamura Ken-Ichi , Orita Masahiro , Sarukura Nobuhiko , Hirano Masahiro , Hosono Hideo 
Published: April 2011

AbstractRoom temperature operation of UV LED is realized for the first time using a hetero p-n junction composed of transparent conductive oxides, p-SrCu2O2 and n-ZnO. Ni/SrCu2O2/ZnO/ITO multi-layered film was epitaxially grown on an extremely flat YSZ (111) surface by a PLD. The grown films were processed by a conventional photolithography, followed by reactive ion etching to fabricate p-n junction diode. The resultant device exhibited rectifying I-V characteristics inherent to p-n junction whose turn-on voltage was about 1.5V. A relatively sharp electro-luminescence band centered at 382nm was generated when applying the forward bias voltage larger than the turn-on voltage of 3V. The red shift in the EL peak was noticed from that of photo-luminescence (377nm), which was most likely due to the difference in the excited state density between the emission processes. The EL band is attributed to transition in ZnO, probably to that associated with electron-hole plasma. The photo-voltage was also generated when the p-n junction was irradiated with UV light of which energy coincided with both exciton and band-to-band transitions in ZnO.
Oxygen Ions Diffusitives in Tin Dioxide Based Thin Films
Authors: Shishkin N.Y. , Zharsky I.M. 
Published: April 2011

AbstractOxygene ions diffusitives in tin dioxide based thin films were measured with electrochemical method. The Pd content 0-3% at. thin films were investigated. The dependencies of the diffusitives vs. content of the layer were obtained.
Pulsed Laser Deposition of Epitaxial SrVO3 Films on (100)LaAlO3 and (100)Si
Authors: Yip P.W. , Wong K.H. 
Published: April 2011

AbstractThin films of SrVO3 have been grown on (100)LaAlO3 and TiN buffered (100)Si substrates by pulsed laser deposition. The films were deposited in temperature range of 450°C – 750°C and under ambient oxygen pressure between 101−6 and 101−2 Torr. Their structural properties were characterized using a four-circle x-ray diffractometer. High quality SrVO3 films were obtained at growth temperatures above 500°C without post annealing. Heteroepitaxial relationship of < 100 >SrVo3 ∥ < 100 >LaAOl3 and <100>SrVo3∥ < 100 >TiN ∥ < 100 >Si were observed for films deposited at ≤ 550°C. X-ray photoelectron spectroscopic studies of the films suggest that the vanadium is mainly tetravalent and pentavalent. Charge transport measurements show that the films vary from semiconducting to highly conducting for different growth conditions. Resistivity of a few micro-ohm cm was recorded for some of the epitaxial SrVO3 films.
Influence of Low Temperature-Grown GaAs on Lateral Thermal Oxidation of Al0.98Ga0.02As
Authors: Ferrer J. C. , Liliental-Weber Z. , Reese H. , Chiu Y.J. , Hu E. 
Published: April 2011

AbstractThe lateral thermal oxidation process of Al0.98Ga0.02As layers has been studied by transmission electron microscopy. Growing a low-temperature GaAs layer below the Al0.98Ga0.02As has been shown to result in better quality of the oxide/GaAs interfaces compared to reference samples. While the later have As precipitation above and below the oxide layer and roughness and voids at the oxide/GaAs interface, the structures with low-temperature have less As precipitation and develop interfaces without voids. These results are explained in terms of the diffusion of the As toward the low temperature layer. The effect of the addition of a Si02 cap layer is also discussed.
Fabrication of Bi2Sr2CaCu2O8 Superconductor Thick Films on Cu Substrates
Authors: Han Sang-Chul , Sung Tae-Hyun , Han Young-Hee , Lee Jun-Seong , Kim Sang-Joon 
Published: April 2011

AbstractWell oriented Bi2Sr2CaCu2O8(Bi2212) superconductor thick films were formed successfully on Cu tapes by liquid reaction between Cu-free precursors and Cu tapes. Cu-free Bi-Sr-Ca-O powder mixtures were screen-printed on Cu tapes and heat-treated at 850-870°C for several minutes in air. Cu-free precursors were composed of BixSrCaOy(x= 1.2-2). In order to obtain the optimum heat-treatment condition, we studied on effects of the precursor composition, heattreatment temperature and time, the screen-printing thickness, and the heat-treatment atmosphere on the superconducting properties of Bi2212 films. Microstructures and phases of films were analyzed by XRD and optical microscopy. The electric properties of superconducting films were examined by the four probe method. At heat-treatment temperature, the specimens were in a partially molten state by liquid reaction between CuO in the oxidized copper tape and the precursors. The non-superconducting phases in the molten state are mixtures of Bi-free phase and Cu-free phases.
Growth Morphology and Electronic Structure of Ultra-Thin TaOx Films on Ag(100)
Authors: Howard M. M. , Ventrice C. A. , Geisler H. , Hite D. A. , Sprunger P. T. 
Published: April 2011

AbstractA study of the growth morphology and electronic structure of TaOx films on the Ag(100) substrate has been performed to determine the properties of ultra-thin TaOx films without the influence of a mixed interfacial oxide (i.e., a disordered SiO2/TaOx interface for growth on Si). The TaO, films were grown by thermal evaporation of Ta in an oxygen atmosphere of 1 × 101−6 Torr. Growth on a Ag(100) surface held at room temperature results in an amorphous TaOx overlayer, as determined by low energy electron diffraction. The onset of ordering of these films occurs for a post-anneal at ∼500°C. A diffraction pattern that corresponds to a multi-domain overlayer structure is observed for anneals at ∼550°C. Deposition of Ta without oxygen results in the formation of Ta islands. These results indicate that there is a very weak adsorbatesubstrate interaction. Photoemission measurements of the TaOx films show the formation of a band gap with the valence band maximum residing at 3.5 eV below the Fermi level. Core level shifts of ∼3.5 eV are observed for the Ta with no indication of metallic Ta at the surface.
Matrix Assisted Pulsed Laser Evaporation Direct Write (MAPLE DW): A New Method to Rapidly Prototype Active and Passive Electronic Circuit Elements
Authors: Fitz-Gerald J.M. , Chrisey D.B. , Piqu A. , Auyeung R.C.Y. , Mohdi R. , Young H.D. , Wu H.D. , Lakeou S. , Chung R. 
Published: April 2011

ABSTRACTWe demonstrate a novel laser-based approach to perform rapid prototyping of active and passive circuit elements called MAPLE DW. This technique is similar in its implementation to laser induced forward transfer (LIFT), but different in terms of the fundamental transfer mechanism and materials used. In MAPLE DW, a focused pulsed laser beam interacts with a composite material on a laser transparent support transferring the composite material to the acceptor substrate. This process enables the formation of adherent and uniform coatings at room temperature and atmospheric pressure with minimal post-deposition modification required, i.e., ≤400°C thermal processing. The firing of the laser and the work piece (substrate) motion is computer automated and synchronized using software designs from an electromagnetic modeling program validating that this technique is fully CAD/CAM compatible. The final properties of the deposited materials depend on the deposition conditions and the materials used, but when optimized, the properties are competitive with other thick film techniques such as screen-printing. Specific electrical results for conductors are < 5X the resistivity of bulk Ag, for BaTiO3/TiO2composite capacitors the k can be tuned between 4 and 100 and losses are < 1-4%, and for polymer thick film resistors the compositions cover 4 orders of magnitude in sheet resistivity. The surface profiles and fracture cross-section micrographs of the materials and devices deposited show that they are very uniform, densely packed and have minimum resolutions of -10 jtm. A discussion of how these results were obtained, the materials used, and methods to improve them will be given
Direct Focused Ion Beam Writing of Printheads for Pattern Transfer Utilizing Microcontact Printing
Authors: Longo David M. , Hull Robert 
Published: April 2011

ABSTRACTWe describe how focused ion beam (FIB) direct write technology may be combined with microcontact printing (μCP) and other pattern transfer techniques to enable nanoscale fabrication of complex patterns over both curved and planar surfaces. Nanoscale printheads are fabricated by direct sputtering or deposition (Pt or SiO2) in the FIB. These printheads are capable of transferring 100 nm features over fields of view up to 1 mm2, onto planar and curved surfaces. We are also investigating the concept of “programmable” printheads by fabrication of individually addressable printhead arrays, coupled with selective desorption of a relevant transfer medium (e.g. hexadecanethiol self-assembled monolayers) by heating or by application of an electric field
Direct Write Techniques for Fabricating Unique Antennas
Authors: Taylor Robert M. , Church Kenneth H. , Culver James , Eason Steve 
Published: April 2011

ABSTRACTThe current fabrication methods used to produce many antennas are limited by variances in the precision and skill levels of individual laborers. These variances slow production and often create inconsistent results. As radio-frequency transmitter and receiver design moves towards higher operating frequencies, the physical dimensions of the supporting antennas decrease. Smaller sizes add new complexities to the fabrication of these antennas. Several designs that may be considered high-performance antennas are difficult to reproduce; many times, they cannot be fabricated at all due to the sophisticated patterning and precision necessary for successful function. Direct-write technologies provide the tools necessary to fabricate unique patterns in two and three dimensions. A demonstration of a directly written antenna, constructed from a silver-based thick-film paste pen-deposited onto cylindrical alumina substrates, is presented for review
Lateral Dye Distribution With Ink-Jet Dye Doping of Polymer Organic Light Emitting Diodes
Authors: Madigan Conor F. , Hebner Thomas R. , Sturm J. C. , Register Richard A. , Troian Sandra 
Published: April 2011

ABSTRACTIn this work we investigate the lateral dye distribution resulting from the dye doping of a thin polymer film by ink-jet printing (UIP) for the integration of color organic light emitting diodes (OLED's). The dye is found to segregate into distinct outer rings following rapid droplet evaporation, while slower evaporation rates are found to significantly reduce (or eliminate) this effect. The dye segregation phenomena are found to depend critically on the mechanisms of droplet evaporation. Good dye uniformity was obtained using a low vapor pressure solvent, and integrated, 250 micron red, green, and blue polymer organic light emitting diodes (OLED's) were fabricated with this technique. These devices had good color uniformity over most of the device area and similar electrical properties to comparable spin-coated devices without IJP