bluuebunny/crossref_metadata_2025_split huggingface dataset:
Strain Dependent Diffusion in the Dry Thermal Oxidation Process of Crystalline Si
Authors: Bjorkman C. H. , Lucovsky G. 
Published: March 2011

ABSTRACTWe have investigated the influence of strain on the rate of thermal oxidation of crystalline Si. This was carried out by performing the oxidation in two steps at 850°C with an intermediate annealing step. It was observed that an anneal at 1050°C increased the oxidation rate 20% compared with an anneal at 850°C. At the same time, the films annealed at higher temperatures exhibited lower levels of strain, as determined by infrared spectroscopy, in the oxide layer grown before the anneal. These results have been interpreted in terms of a strain dependent diffusion model for the thermal oxidation process.
Transport in Compounds Containing a Dispersed Second Phase.
Authors: Bruce Wagner J. 
Published: March 2011

ABSTRACTThe introduction of a dispersion of small (≃ 1μ1m) insulating particles into an ionic conductor results in an increase in the ionic conductivity. This behavior is not in accord with classical theory. A number of different examples such as a dispersion of a metallic conductor in a semiconductor, a dispersion of an insulator in a semicondutor, and a dispersion of a metallic conductor in an ionic conductor all yield unusual transport behaviors when the surface area to volume ratio of the dispersoid is large. Under such conditions, a space charge layer or double layer adjacent to the dispersoid must be considered. Practical applications such as solid electrolytes, electrodes, corrosion systems and geological systems were discussed.
Densification of Shock-Treated Aluminum Nitride and Aluminum Oxide
Authors: Beauchamp E. K. , Graham R. A. , Carr M. J. 
Published: March 2011

ABSTRACTThe structures of aluminum nitride and aluminum oxide powders have been modified by explosive shock treatment at pressures from 4 to 27 GPa. Shockinduced dislocations in AlN were apparently responsible for enhancement in hot pressing behavior. In Al2O3 an increase 3 to 4 times in densification rates after shocking resulted-from rapid sintering of aggregates in the powder.
Transmission Electron Microscopy of Shock-Modified and Annealed Rutile
Authors: Carr M. J. , Graham R. A. , Morosin B. , Venturini E. L. 
Published: March 2011

ABSTRACTThe annealing behavior of shock modified rutile (TiO2) powder was studied by transmission electron microscopy, x-ray line broadening, and electron spin resonance. Specimens were examined in the as-received and as-shocked conditions, and in shocked and annealed conditions after one hour at 475° or 1000°C. The dislocations generated by the shock treatment were found to persist essentially unaltered through the 475°C anneal. Substantial recovery was observed after the 1000°C anneal.
Metallic Microwave Conductivity in Shock-Loaded Rutile
Authors: Venturini E. L. , Graham R. A. 
Published: March 2011

ABSTRACTElectron spin resonance (ESR) has been used to characterize the paramagnetic defects present in both single crystal and powder rutile (TiO2) subjected to explosiveshock loadingand preserved for post-shock study. The Ti+3defect concentration produced by the shock process is an order of magnitude larger than values reported for vacuumreduced rutile. The ESR lineshape is characteristic of a conducting material, and the estimated microwave resistivity in the shock-loaded powder is more than an order of magnitude lower than the minimum dc value measured in vacuum-reduced rutile. It appears that shock-wave loading leaves the rutile in a defect state not achieved in prior work.
Status, Needs, and Opportunities for Structural Ceramics in Advanced Heat Engines
Authors: Tennery V. J. 
Published: March 2011

ABSTRACTThe potential for using structural ceramic materials in components of advanced heat engines including the gas turbine and adiabatic diesel has recently been demonstrated by results in DOE and DOD engine development programs. Status of these efforts, technical needs for candidate ceramic materials, and research opportunities in new DOE and NASA ceramic technology programs oriented to heat engines are reviewed.
Modification of Point Defects in Quartz for Device Applications
Authors: King J. C. , Koehler D. R. 
Published: March 2011

ABSTRACTImpurity centers in quartz play a significant role in the behavior of precision crystal resonators subjected to ionizing radiation. The substitutional Al center, charge compensated by Na, Li, H or a hole, is now known to be the primary contributing factor in most radiation-induced effects. Acoustic loss measurements, ESR measurements, optical studies and IR studies of these defects, over extended temperature ranges, have contributed substantially to our understanding of the impurity centers' role. Radiation-induced frequency and acoustic loss changes in quartz crystal resonators are now understood in terms of the evolving character of the defect center in a radiation field. This understanding has prompted material modification efforts such as high temperature electrolysis and doping technologies which permit, for instance, the fabrication of frequency control devices that are little affected by hostile environments.
Displacive Phase Transformation in Vanadium - Substituted Lanthanum Niobate
Authors: Aldred A. T. , Chan S.-K. , Grimsditch M. H. , Nevitt M. V. 
Published: March 2011

ABSTRACTThe displacive transformations in complex oxides of the type LaNb1-xVxO4 has been studied by x-ray diffraction and Raman scattering for 0 < x < 0.3. X-ray diffraction results indicate that the transformation from the tetragonal high temperature structure (C4h6) to the monoclinic low-temperature structure (C2h6) is higher than first order and that the transformation temperature Tc is depressed significantly by V substitution. Raman scattering results show that the force constant between the nearest (Nb, V)O4 tetrahedral units behave uniquely compared to others. It softens at Tc as a function of composition and it also softens as a function of temperature as Tc is approached from above.
Quantitative Depth Profiling Resonance Ionization Mass Spectrometry of III-V Heterostructure Semiconductors
Authors: Emerson A. B. , Downey S. W. , Kopf R. F. 
Published: March 2011

ABSTRACTResonance ionization mass spectrometry (RIMS) of neutral atoms sputtered from III-V heterostructure semiconductor materials provides quantitative information about the dopant position near interfaces. The prerequisite for quantitative results is the saturation of the ionization step. The absolute signals are affected by primary ion beam parameters which affect sputter yield, atomization efficiency and quantum state partitioning, but not ionization efficiency. We have found that matrix effects are minimal and use RIMS results to help elucidate dopant migration near interfaces and interpret SIMS matrix effects. Device performance and understanding of materials growth are both aided.
Impact of a Vicinal Growth Surface on AlAs / GaAs Superlattice Layer Thickness Measurements with Double Crystal X-ray Diffraction
Authors: Leiberich A. , Levkoff J. , Robertson A. 
Published: March 2011

ABSTRACTMicroelectronic devices require deposition of sequences of thin epitaxial layers, with individual layer thicknesses in some instances specified to within tolerances of the order of inter-atomic spacings. Double crystal X-ray diffraction provides measurements of superlattice layer thicknesses to a resolution of the order of inter-atomic spacings, provided diffraction line shifts originating from substrate wafer misalignments are accounted for.
Semi-Insulating InP Grown by MOCVD
Authors: Feng M. S. , Wu C. C. , Lin K. C. , Chan S. H. , Chen C. Y. 
Published: March 2011

ABSTRACTFe (C5H5)2 and Fe (CO)5 were used as the 3d transition metal dopants in semi-insulating InP epitaxial layer grown by MOCVD. From the bright and dark field images of the TEM analysis, many precipitates were observed. Three extra peaks of the X-ray diffraction were found. The peaks of free-exciton recombination, donor-acceptor transition and the recombination of bound exciton with phonon emission were observed in the short wavelength range. Two Fe related peaks was observed at 0.7079 eV and 0.6897 eV. For a wide range (10–600) of In/Fe mole fraction, the resistivity keeps at high values (about 108 Ω -cm) and appears the highest resistivity of 5 × 108 Ω -cm for 1 μ m layer.
Constant Depth DLTS Measurements on Compound Semiconductors
Authors: Denenberg David , Blew Austin 
Published: March 2011

ABSTRACTThis paper describes a useful measuring technique enabling Deep Level Transient Spectroscopy [DLTS] on compound semi-conductors. We will report on the methodology of DLTS measurements using newly available software for Miller Feedback Profilers. This method has the advantages of using the constant depth capabilities of the profiler. The combination instrument offers flexibility in limited clean room space.
Damage Introduced by Chdamage Introduced by CH4/H2 Reactive Ion Etching in Pseudomorphic AlGaAs/InGaAs MODFETs
Authors: Pereira R. , Van Hove M. , De Raedt W. , Van Hoof C. , Borghs G. , Van Rossum M. , Braspenning R. H. , Eijkemans T. J. , Van Es C. M. , Wolter J. H. 
Published: March 2011

ABSTRACTThe damage introduced by CH4/H2 reactive ion etching (RIE) and its recovery after thermal annealing has been investigated by Hall measurements and low temperature photoluminescence (PL) on pseudomorphic AlGaAs/InGaAs modulation doped structures. After plasma exposure, the PL intensity has significantly decreased and shifted in energy. In order to study the recovery of the damage introduced by the plasma, thermal annealing was done at temperatures between 350 and 500°C. We observed that the luminescence emission is totally recovered after annealing at 450°C. Hall measurements at room temperature (RT) and at 77K showed that the electrical characteristics of these structures can be restored only after thermal annealing at 500°C.The optimised etching conditions have been applied in a fabrication process for submicron dry gate recessed pseudomorphic delta-doped AlGaAs/InGaAs modulation doped field effect transistors (MODFETs). For a 0.25 mm gatelength device the maximum DC transconductance value was as high as 680 mS/mm. The same value was extracted from measurements at 15 GHz.
CHF3and NH3Additives for Reactive ion Etching of GaAs Using CCl2F2and SICI4
Authors: Din Kuen-Sane , Chi Gou-Chung 
Published: March 2011

ABSTRACTTwo fundamental requirements for RIE are the formation of nearly volatile etch products and sufficiently high physical bombardment to remove all substances on the surface. In this study, the GaAs wafer was in-situ pretreated with NH3or CHF3plasma prior to actual etching process. The main etchants are CCl2F2and SiCl4. By adding these additives to the main etch gases, the resulting etch performance was significantly affected. For instance, DC self-bias of CCl2F2plasma is relatively low and can increase with such gas addition, thus the etching properties related to physical bombardment change too. CHF3improve GaAs etch rate in CCl2F2through increasing concentration of reactive chlorine-containing species. While CHF3enhance etch rate in SiCl4plasma. The as etched samples were examined with X-ray photoelectron spectroscopy. Details of the experimental results will be described.
Formation of Ohmic Contacts to InP by Means of Rapid Thermal Low Pressure (Metalorganic) Chemical Vapor Deposition (RT-LPMOCVD) Technique
Authors: Katz A. , Feingold A. , Pearton S. J. , Nakahara S. , Lane E. , Geva M. 
Published: March 2011

ABSTRACTThe viability of forming an ohmic contact to InGaAs/InP structures by means of a load-locked RT-LP(MO)CVD integrated process, was demonstrated. The wafer was loaded into the reactor chamber and was exposed to a sequence of dry and in-situ processes which led to the formation of an ohmic contact. After an in-situ cleaning of the wafer through a thermal cycle at 500°C under a flow of tertiarybutylphosphine (TBP), which provided the needed free hydrogen for a mild etching of the surface, however with an over pressure of P to eliminate surface degradation, a layer of silicon oxide (SiOx ) was rapid thermal chemical vapor deposited (RT-CVD) onto the InGaAs/InP sample via a rapid thermal cycle (500°C,30 s) in a low pressure O2 and 2% diluted SiH4. Dry etching of 50–150 μm wide contact stripes was carried out using a contact stencil mask by an electron-cyclotron resonance (ECR) dry etching. Subsequently the wafer was reloaded through the load-lock to the main chamber and a TiNx layer were selectively deposited into the via-holes and processed to provide an ohmic contact to the InGaAs/InP substrate. Finally, a blanket deposition of conducting cap layer was realized by means of RT-LP(MO)CVD. This work provides a solid demonstration to the feasibility of the single-wafer-integrated-process (SWIP) as an approach to replace the batch process traditionally used for manufacturing the InP-based optoelectronic devices.
Improvement of Ohmie Contacts on GaAs with In-Situ Cleaning
Authors: Ren F. , Pearton S. J. , Fullowan T. R. , Hobson W. S. , Chu S. N. G. , Emerson A. B. 
Published: March 2011

ABSTRACTAn in-situ argon ion-mill clean step prior to ohmic metal deposition combined with a Mo barrier layer AuGe based ohmic metallization which is compatible with dry-etch process have been demonstrated to improve the uniformity of the contact parameters and reduce the contact resistance. After ion mill cleaning, the native oxide regrowth of MBE grown GaAs and AlGaAs layers in vacuum chamber was also studied to optimize the processing. These oxide layers were identified as the cause of problems in the formation of good ohmic contacts to the GaAs or AlGaAs, the Mo diffraction barrier also reduced the contact resistivity with excellent adesion, smooth morphology, and sharp edge definition.
Investigation of Ge, As, and Au Diffusion in Non-Alloyed Epitaxial Au-Ge Ohmic Contacts to n-GaAs Using Secondary Ion Mass Spectroscopy Backside Sputter Depth-Profiling
Authors: LEE H. S. , Lareau R. T. , Schauer S. N. , Moerkirk R. P. , Jones K. A. , Elagoz S. , Va Vra W. , Clarke R. 
Published: March 2011

ABSTRACTA SIMS backside sputter depth-profile technique using marker layers is employed to characterize the diffusion profiles of the Ge, As, and Au in the Au-Ge contacts after annealing at 320 C for various times. This technique overcomes difficulties such as ion beam mixing and preferential sputtering and results in high depth resolution measurements since diffusion profiles are measured from low to high concentration. Localized reactions in the form of islands were observed across the surface of the contact after annealing and were composed of Au, Ge, and As, as determined by SIMS imaging and Auger depth profiling. Backside SIMS profiles indicate both Ge and Au diffusion into the GaAs substrate in the isalnd regions. Ohmic behavior was obtained after a 3 hour anneal with a the lowest average specific contact resistivity found to be ∼ 7 × 100−6 Ω- cm2.
Ambipolar Lifetimes in GaAs/AlGaAs Self Electro-Optic Effect Devices
Authors: Swaminathan V. , Freund J. M. , Focht M. W. , Guth G. D. , Przybylek G. J. , Smith L. E. , Leibenguth R. E. , D'Asaro L. A. 
Published: March 2011

ABSTRACTThe forward current-voltage (I-V) characteristics of GaAs/AlGaAs Self Electro-optic Effect Device (SEED) p-i-n diodes were measured. The I-V curves exhibited a diode like behavior with an ideality factor of 2 for voltages in the range 0.5–1.25V. In this region, the diode series resistance varied inverse proportional to the forward current with the constant of proportionality being equal to this voltage drop in the i-region. From an analysis of the experimentally obtained voltage drop, the ambipolar lifetime was determined. For the standard device whose i-region had a multi quantum well structure consisting of 60 periods of 100Å undoped GaAs wells and 65Å undoped Al0.30Ga0.70As barriers, the ambipolar lifetime was found to be 79.6±3 psec for a 30×30 μm2mesa device and 92 ± 4 psec for a 100×100 μm2mesa device. When the barrier width was reduced to 35Å or when the barrier Al composition decreased to 0.2, no significant change in the ambipolar lifetime was measured. Since previous measurements have indicated that decreasing the barrier width or height greatly enhances carrier escape from the wells during the operation of the GaAs/AlGaAs p-i-n diode as a photodetector, it is inferred that the carrier escape and collection times are smaller than ∼ 80–90 psec.
Comparison of Dislane and Tetraethyltin as Gaseous Dopants for Growth of n-GaAs and O-AlGaAs by MOMBE
Authors: Wisk P. , Abernathy C. R. , Pearton S. J. , Ren F. , Fullowan T. , Lothian J. 
Published: March 2011

ABSTRACTWe have investigated the effect of growth temperature and V/III ratio on dopant incorporation from disilane (Si2H6) and tetraethyltin (TESn) over the temperature range 475°C-525°C during growth of GaAs by metal organic molecular beam epitaxy (MOMBE). Increasing V/III ratio produced only a slight decrease in the dopant concentration while increasing growth temperature resulted in slighdy higher dopant levels. Addition of Al and H to the growth surface via introduction of trimethylamine alane had no apparent effect on dopant incorporation. No significant differences were observed in the incorporation behaviors of Si2H6 and TESn, and both sources yielded comparable base-collector junction behavior when used for growth of heterojunction bipolar transistors (HBTs).
Raman Characterization of AlGaAs Superlattice Channel Waveguide Structure formed by CIB and FIB Implantation
Authors: Choo A. G. , Gupta V. , Jackson H. E. , Boyd J. T. , Steckl A. J. , Chen P. , Weiss B. L. , Burnham R. D. 
Published: March 2011

ABSTRACTRaman scattering has been used to characterize lattice damage and impurity-induced compositional disordering in AlGaAs superlattice suitable for optical waveguiding. The degree of damage induced by both conventional ion beam (CIB) implantation and focused ion beam (FIB) implantation is studied using a spatial correlation model to interpret the Raman spectra. FIB implantation is found to induce slightly more damage than CIB implantation for doses of 8×1013 cm−2 and 4×1014 cm−2. and significantly more damage with 2×1015 cm2 compared to CIB implantations of the same dose. Suitable FIB implantation and rapid thermal annealing (RTA) conditions which provide compositional mixing were determined using Raman and photoluminescence spectroscopy. Using these conditions, an optical channel waveguide in AlGaAs superlattice formed by FIB-induced compositional intermixing is demonstrated.
Excitation Power Dependence of Photoluminescence in CIB and FIB Implanted Superlattices
Authors: Choo A. G. , Jackson H. E. , Chen P. , Steckl A. J. , Gupta V. , Boyd J. T. 
Published: March 2011

ABSTRACTLow temperature photoluminescence spectra have been used to characterize conventional ion beam (CIB) and focused ion beam (FIB) implanted superlattices. The excitation dependence of the single scan FIB is found to be significantly different from CIB and multiple scan FIB implantations which are similar. The peak position of the donor-acceptor transition is observed to change to higher energies significantly slower with excitation intensity for the single scan FIB case when compared to the multiple scan FIB and CIB cases. Simple models to describe these effects are briefly discussed.
Determination of Ga Self-Diffusion Coefficient in GaAs
Authors: Tan T. Y. , Yu S. , Gösele U. 
Published: March 2011

ABSTRACTA quantitative determination of the contributions of the triply-negatively charged Ga vacancies and of the doubly-positively charged Ga self-interstitials to Ga self-diffusion coefficient in GaAs has been carried out. Unde thermal equilibrium and intrinsic conditions, the contribution is characterized by an activation enthalpy of 6 eV for As-rich crystals and of 7.52 eV for Ga-rich crystals, while the contribution is characterized by an activation enthalpy of 4.89 eV for As-rich crystals and of 3.37 eV for Ga-rich crystals.
Mechanism of Cr Diffusion in GaAs
Authors: Yu S. , Tan T. Y. , Gösele U. 
Published: March 2011

ABSTRACTDiffusion of substitutional Cr atoms (Crs) in GaAs results from the rapid migration of interstitial Cr atoms (Cri) and their subsequent changeover to occupy Ga sites (or vise versa), a typical substitutional-interstitial diffusion (SID) process. There are two possible ways for the Cri-Crs changeover to occur: the kick-out mechanism in which Ga self-interstitials are involved, and the dissociative mechanism in which Ga vacancies are involved. The Crs indiffusion profiles are of characteristic shapes indicating the dominance of the kick-out mechanism, while the Crs outdiffusion profiles are error-function shaped, indicating the dominance of the dissociative mechanism. In this study, an integrated SID mechanism, which takes into account the effects of both the kick-out and dissociative mechanisms, is used to analyze Cr diffusion results. Going beyond just qualitative consistency, the Cr in- and outdiffusion features in GaAs are explained on a quantitative basis. In this model the kick-out mechanism dominates Cr indiffusion while the dissociative mechanism dominates Cr outdiffusion. Parameters used to fit existing experimental results provided quantitative information on the Ga self-interstitial contribution to the Ga self-diffusion coefficient.
Implantation-Induced Voids for Thermally Stable Electrical Isolation in GaAs
Authors: Ko K. Y. , Chen Samuel , Tong S. , Braunstein G. 
Published: March 2011

ABSTRACTMicroscopic voids, formed from the condensation of supersaturated vacancy point defects, were recently discovered in implanted and annealed GaAs. These defects have been shown to suppress carrier concentrations. Since voids are formed only at relatively high temperatures (> 650 °C), the possibility exists that voids can be used for thermally stable implant isolation. In this paper, we report on the formation of highly resistive layers in GaAs, created by Al+ implantation and annealing in the 700–900 °C range. In samples containing voids, their sheet resistivities increased by about six orders of magnitude from the as-grown value. Formation of these thermally stable, high resistivity regions is different from the conventional H or O implant isolation techniques, which use lattice damage to create the isolation characteristics. However, since lattice damage is annealed out between 400–700 °C, this type of isolation becomes ineffective at high processing temperatures. By contrast, voids are stable at high processing temperatures, and potential advantages of using such defects for device isolation in GaAs are pointed out.
A Purely Spectroscopic Technique for Determining Energy Band Offsets in Quantum Wells
Authors: Koteies Emil S. 
Published: March 2011

ABSTRACTWe have developed a novel experimental technique for accurately determining band offsets in semiconductor quantum wells (QW). It is based on the fact that the ground state heavy- hole (HH) band energy is more sensitive to the depth of the valence band well than the light-hole (LH) band energy. Further, it is well known that as a function of the well width, Lz, the energy difference between the LH and HH excitons in a lattice matched, unstrained QW system experiences a maximum. Calculations show that the position, and more importantly, the magnitude of this maximum is a sensitive function of the valence band offset, Qy, which determines the depth of the valence band well. By fitting experimentally measured LH-HH splittings as a function of Lz, an accurate determination of band offsets can be derived. We further reduce the experimental uncertainty by plotting LH-HH as a function of HH energy (which is a function of Lz ) rather than Lz itself, since then all of the relevant parameters can be precisely determined from absorption spectroscopy alone. Using this technique, we have derived the conduction band offsets for several material systems and, where a consensus has developed, have obtained values in good agreement with other determinations.