bluuebunny/crossref_metadata_2025_split huggingface dataset:
Combined Microstructure X-Ray Optics; Multilayer Diffraction Gratings
Authors: Barbee Troy W. 
Published: March 2011

ABSTRACTMultilayers are man-made microstructures engineered to vary in depth that are now of sufficient quality to be used as x-ray, soft x-ray and extreme ultraviolet optics. Gratings are in-plane man-made microstructures which have been used as optic elements for most of this century. Joining of these two optical elements to form combined microstructure optics has the potential for greatly enhancing both the resolution and the throughput attainable in these spectral ranges. Experimental results for multilayer gratings are presented and discussed. It will be demonstrated that multilayer diffraction gratings act as x-ray prisms and are high efficiency dispersion elements.
Magnetic Superlattices
Authors: Schuller Ivan K. 
Published: March 2011

ABSTRACTMagnetic superlattices serve as model systems for the study of thin film, interfacial, proximity, coupling and superlattice phenomena. Due to these phenomena, the physical properties of magnetic superlattices can be tuned in a reproducible fashion by proper control of the preparation process.Magnetic measurements in conjunction with detailed structural characterization provide a fruitful area of research, especially in understanding basic phenomena in magnetism. We describe here briefly a few experimental examples from our work which illustrate the possibilities magnetic superlattices offer for the study of basic phenomena in magnetism.
On the Existence of Multiple Equilibrium States in Strained-Layer Superlattices
Authors: Johnson William C. 
Published: March 2011

ABSTRACTUsing recent results from the thermodynamics of stressed solids, two-phase coexistence in a simple binary strained-layer superlattice is examined. We show that for a given temperature and overall composition of the superlattice, there can exist more than one linearly stable, equilibrium thermodynamic state. That is, there may exist several combinations of relative thickness of the phases and corresponding phase compositions that minimize the free energy of the system. The equilibrium state observed experimentally can, therefore, be influenced by the processing path.
Spectroscopy of Impurities and Complex Defects in Silicon in Zlectric and Microwave Fields
Authors: Godlewski M. , Weman H. , Wang F. P. , Monemar B. , Chen W. M. , Zhao Q. X. 
Published: March 2011

ABSTRACTWe report a detailed study of the photoluminescence (PL) intensity of bound excitons (BE:s) in silicon, related to shallow impurities and deep complex defects, as a function of DC and high frequency AC (9GHz) electric fields. Two experimental approaches are presented. The first involves a simultaneous recording of PL and photocurrent under pulsed DC excitation. The second utilizes the optically detected cyclotron resonance (ODCR) technique, which allows detection of cyclotron resonance (CR) via the resonancetransition- induced changes of BE PL intensity. The mechanism responsible for the PL changes is shown to be the impact ionization of BE:s by hot free carriers. Effects of sample inhomogeneities in these experiments are also discussed.
Dislocation Dynamics During the Czochralski Growth of Silicon
Authors: Tsai C. T. , Dillon O. W. , Angelis R. J. De 
Published: March 2011

ABSTRACTThe thermal stresses induced by temperature variations that exist during steady-state Czochralski growth produce plastic deformations in the crystal by dislocation motion and generation. The temperature variations in the crystal are calculated numerically by the finite element method (FEM). Employing the Haasen-Sumino viscoplastic response function for silicon and the calculated temperature profile, the thermal stresses, the dislocation densities, and the residual stresses in the crystal are also calculated. Only low dislocation densities are of interest and hence the associated viscoplastic deformations are found to be small. The assumption is made that there is a very low dislocation density along the solid-melt interface. The Haasen-Sumino material model is modified to include a back-stress to account for the locking effects due to the impurity concentration in the crystal. This analysis provides guidance for growing large diameter crystal of materials with known constitutive relations which have a low dislocation density and low thermal stresses.
Influence of Oxygen and Boron on Defect Production in Irradiated Silicon
Authors: Drevinsky P. J. , Caefer C. E. , Tobin S. P. , Mikkelsen J. C. , Kimerling L. C. 
Published: March 2011

ABSTRACTIntroduction rates of dominant defects have been determined for electron-irradiated, p-type silicon as a function of oxygen and boron concentration. Samples included those with oxygen content ranging from 8 × 1015 to 7 × 1017 cm−3. Initial results are described for samples with measured carbon content varying from 2 × 1015 to 6 × 1016 cm−3. Competing defect reactions involving the interstitial defects, Bi and Ci, and oxygen, boron, and carbon are observed. The identities of an electron trap (Bi-Oi) and a hole trap (Bi-Bs) have been clarified.
Tem Study of Metal Impurity Precipitates in the Surface Regions of Silicon Wafers
Authors: Seibt M. , Graff K. 
Published: March 2011

ABSTRACTThe precipitation behaviour of the transition metals Co, Ni, Cu and Pd has been studied by means of conventional and high - resolution electron microscopy. Special experimental conditions for specimen preparation were chosen, which lead to the formation of haze. These conditions were the same for all metals. Therefore, a direct comparison of the respective precipitation phenomena was possible. Co and Ni were found to precipitate as Si - rich silicide particles exhibiting various morphologies attributed to different stages of particle growth and ripening. It is shown that the generation of Si- self - interstitials (and vacancies) plays a minor role in the preci-pitate formation. On the other hand Cu and Pd precipitate as metal - rich silicide particles. They form star - like colonies consisting of small particles and extended extrinsic edge - type dislocation loops. The precipitation behaviour of these two met-als is governed by the generation of Si - self - interstitials due to the large misfit of the metal - rich silicide particles.
Hydrogen-Induced Defects in Silicon by CF4/x% H2 (0≤x≤ 100) RIE and H2 Plasma
Authors: Jeng Shwu-Jen , Oehrlein Gottlieb S. , Scilla Gerald J. 
Published: March 2011

ABSTRACTThe extended defects induced by hydrogen diffusion in silicon during the process of (1) CF4/x% H2(0≤x≤100) reactive ion etching, or (2) hydrogenation in H2 plasma, or (3) passivation of boron acceptors in H2 plasma, are studied by high resolution electron microscopy and secondary ion mass spectrometry. In reactive ion etched Si, a higher density of {111} planar defects are produced as the concentration of H2 in the etching gas and/or the overetch time is increased. The Si surface appears rough after reactive ion etching. Similar {111} planar defects are also found in Si after a H2 plasma treatment at 200°C for 3 hours, while the Si surface remains smooth. Boron im-plantation (30keV, 1015 at/cm2) and furnace annealing (1000°C, 30 min) processes are found to introduce stacking faults and perfect dislocation loops into silicon wafers. After subsequent exposure of boron implanted Si to a H2 plasma (200°C, 3 hours), microprecipitates associated with dislocation loops are observed.These results indicate that the apparent surface roughness (top 30 Å layer) in reac-tive ion etched Si is caused by energetic ion bombardment (∼500 eV). However, the {111} planar defects in CF4/x% H2(x>40%) reactive ion etched Si and the {111} planar defects and microprecipitates in H2 plasma treated Si are induced by the super-saturation of hydrogen diffused into Si during the plasma treatment process.
Localization of Hydrogen in B and in Doped Silicon by ion Channeling and PAC
Authors: Wichert Th. , Skudlik H. , Carstanjen H. -D. , Enders T. , Deicher M. , Grübel G. , Keller R. , Song L. , Stutzmann M. 
Published: March 2011

ABSTRACTThe lattice site of H/D atoms in silicon doped with B and 111In atoms is investigated using the ion channeling and perturbed γγ angular correlation (PAC) technique. The results indicate that at 295 K the antibonding site is occupied by H/D and that this site is easily transformed into a near tetrahedral site under the influence of an analyzing ion beam. Based on PAC results, the population of a second site, possibly a bond-center site, is expected at low temperatures.
Hydrogen Injection Into P-Type Silicon By Chemical Etching
Authors: Tavendale A. J. , Williams A. A. , Pearton S. J. 
Published: March 2011

ABSTRACTHydrogen injection with B acceptor neutralization in p-type Si etched in HNOs and HF acid mixtures has been confirmed by isotopic [D] substitution and secondary ion mass spectrometry [SIMS] profiling. Quantitative measurements of the near-surface Injected hydrogen were made following field-aided, in-bulk transport [H+ drift] in reverse-bias annealed Schottky diodes from etched, B-doped Si. Chemical-etch injection is found to be self limiting with neutralization observed over a depth which is characteristic of the base material acceptor concentration and in the range 6–8 extrinsic Debye lengths, indicating that holes are essential in the injection mechanism. An effective diffusivity for hydrogen in etched p-Si of ∼ 2 × 10−9 cm2 s−1 was measured [300 K], considerably higher than previously reported.
Optically Detected Magnetic Resonance of Zinc Interstitials and Frenkel Pairs in ZnSe
Authors: Watkins G. D. , Rong F. , Barry W. A. , Donegan J. F. 
Published: March 2011

ABSTRACTOptical detection of magnetic resonance (ODMR) is reported for ZnSe irradiated by 2.5 MeV electrons in situ at 4.2K. Interstitial zinc atoms are detected in both isolated form and paired with zinc vacancies (Frenkel pairs) of many resolved discrete separations. The isolated interstitial produces a deep second donor state (+/++) at ∼Ec -0.8 eV and its activation energy for migration is estimated to be ∼0.6–0.7 eV. The Frenkel pairs give rise to efficient localized donor-acceptor recombination luminescence and the exchange interactions between the electron and hole on the two partners are measured directly by ODMR.
Hydrogen in III–V Semiconductors
Authors: Dautremont–Smith W. C. 
Published: March 2011

ABSTRACTThe reversible introduction of atomic hydrogen into III–V semiconductors reduces the active concentrations of shallow donor and acceptor levels, as well as a variety of deep levels. Dissociation of the hydrogen-containing complexes by thermal annealing can restore the original active concentrations, and aid in the characterization of the complexes involved. Hydrogen is in-diffused at temperatures typically in the 150 to 300°C range, most simply from an H2 plasma.In GaAs, the III–V compound which has been subjected to the most hydrogenation studies, carrier concentrations are reduced (by up to many orders of magnitude) in both n- and p-type material. Hydrogen diffusion depths are dependent on dopant concentration, but for similar doping levels, diffusion is always deeper into p-type GaAs. In addition, the type of plasma exposure strongly influences the depth of H diffusion, with low frequency, direct exposure producing the greatest penetration depth. A variety of deep level defects in bulk material (including EL2) and in MBE-grown layers can be passivated, and partial passivation of interface-related defects in GaAs-on-Si has been demonstrated. Reactivation kinetics are dependent on the nature of the dopant or defect, with the passivation of p-GaAs being less stable than that of n-GaAs. Recent infra-red absorption studies have confirmed the formation of a donor-hydrogen complex in n-GaAs, in contrast to an As-H complex in p-GaAs. In GaAIAs, acceptors, donors, and the DX center have been passivated. In some cases, the defect passivation has greater thermal stability than that of the shallow levels, a property of potential benefit. Recently demonstrated applications of hydrogenation include an MBE GaAs MESFET with a hydrogenated channel, and a GaAs/GaAIAs double heterostructure laser with current guiding provided by resistive hydrogenated regions.
Photoluminescence Detection of Shallow Impurity Neutralization in Iii-V Compound Semiconductors
Authors: Weber Jörg , Singh Mandeep 
Published: March 2011

ABSTRACTWe studied the low-temperature photoluminescence (PL) of several III–V compound semiconductors before and after hydrogen-plasma treatment. Drastic intensity changes of the bound exciton luminescence after hydrogen plasma treatments indicate a neutralization of impurities by the atomic hydrogen. In GaP, neutralization of the sulfur donor as well as the acceptors (C, Zn, Cd) is observed. The intense luminescence of the exciton bound to isoelectronic N in GaP is fully quenched by hydrogen plasma treatment.
Intrinsic Defects in GaAs - the Case of El2
Authors: Von Bardeleben H. J. , Stievemard D. 
Published: March 2011

ABSTRACTThe arsenic antisite-arsenic interstitial pair model for the stable configuration of the EL2 defect in GaAs has stimulated new experimental and theoretical studies, the results of which lead to additional support for this model. Recent theoretical studies, taking into account the effect of a Jahn Teller distortion of the T2 Asi levels have given an insight into the stability and the electronic structure of the defect pair. Further, ODENDOR studies have directly confirmed this model and allowed one to specify the lattice location and the charge state of the Asi ion. The pair structure of this defect implies a reconsideration of the charge states of the EL2 defect, as well as the origin of the optical absorption bands for which transitions on the Asi ion and intracenter bands have also to be considered. The model leads further to a description of the metastable configuration : an arsenic molecule at the gallium vacancy site, the electronic structure of which is calculated. The vacancy related defects, known from electron irradiation studies, are not detected in LEC grown GaAs as native defects.
Metastable Defects in Silicon
Authors: Chantre A. 
Published: March 2011

ABSTRACTOriginally discovered in compound semiconductors, metastability is now being observed for many defects in silicon as well. Simple considerations indeed suggest the existence of alternate, metastable configurations for ab large variety of defect complexes, even as simple as ionic pairs. Techniques to isolate these excited defect configurations are also now well established, and being used routinely in a number of laboratories. This paper will review the recent achievements in this field. Selected examples will be described to illustrate the status of research on metastable defects in silicon.
Effects of Growth Conditions on EL-2 Concentration in OMVPE- GaAs
Authors: Venkatasubramanian R. , Lee W. I. , Ghandhi S. K. , Borrego J. M. 
Published: March 2011

ABSTRACTWe have studied, using DLTS, the EL-2 concentration in unintentionally doped OMVPE n-GaAs as a function of growth conditions such as partial pressure of Arsine, Trimethylgallium and growth temperature. The partial pressure dependencies are used to develop a model for the formation of EL-2 in the OMVPE process. The EL-2 concentration also shows a near inverse dependence on growth temperature.
Properties of the EL2 Level in Organometallic Ga1−xAlxAs
Authors: Cherifa A. Ben , Azoulay R. , Guillot G. 
Published: March 2011

ABSTRACTWe have studied by means of deep level transient spectroscopy and photocapacitance measurements deep electron traps in undoped Ga1−xAlxAs of n-type grown by metalorganic chemical vapor deposition with 0≤x≤ 0.3. A dominant deep electron trap is detected in the series of alloys. Its activation energy is found at EC-0.8 eV in GaAs and it increases with x. Its concentration is found nearly independent of x. For the first time we observed for this level in the Ga1−xAlxAs alloys, the photocapacitance quenching effect typical for the EL2 defect in GaAs thus confirming clearly that EL2 is also created in MOCVD Ga1−xAlxAs.
Absolute Pressure Derivatives of Deep Level Defects in III-V Semiconductors
Authors: Nolte D. D. , Walukiewicz W. , Hailer E. E. 
Published: March 2011

ABSTRACTBased on transition metal reference levels, we present absolute pressure derivatives for band-edges in GaAs and InP and defects in GaAs. The defect deformation potentials are directly related to the electron-lattice coupling which drives lattice relaxation around the defects. We find an exceedingly large inward lattice relaxation of the EL2 defect in GaAs upon electron emission.
Thermal Annealing and Cooling-Rate Dependent Electronic Properties of Bulk GaAs Crystals
Authors: Parsey J. M. , Asom M. T. , Kimerling L. C. , Sauer R. , Thiel. F. A. 
Published: March 2011

ABSTRACTChanges in the electronic properties of bulk GaAs crystals, grown from melts of varied As:Ga ratios, and Si-donor concentrations, were investigated by annealing in the temperature range 850°C to 1050°C. We found a gradual reduction of the free carrier concentration, a corresponding decrease in the luminescence spectral intensity, and a suppression of the near band-edge peaks with annealing time at any temperature. Deep level and impurity concentrations remained essentially constant. The magnitude of these changes was found to be determined predominantly by the annealing time and temperature, and the starting composition of the material We argue for a non-radiative native acceptor defect, or defect complex, forming during the annealing cycle. We present here the thermodynamic interpretation for this behavioi in terms of point defect equilibria.
Time Resolved Photoluminescence of Yb in InP
Authors: Klein P. B. 
Published: March 2011

ABSTRACTTime resolved photoluminescence (PL) measurements of the internal 4f-4f transitions of Yb3+ have been carried out in InP and GaP. In InP a nonexponential component is observed in the PL decay, and is interpreted in terms of carrier capture by nonequilibrium Yb3+. At low temperatures the exponential component is found to be much faster (≈12.5 μsec) than expected, and is tentatively associated with a weak coupling to resonant valence band states. As the temperature is increased, the PL intensity and the exponential component of the excited state lifetime are quenched with a thermal activation energy of ≈0.1 eV. This is interpreted as being due to the emission of a hole into the valence band by the neutral Yb acceptor.
Observation of the Ga Self-Interstitial Defect in GaP
Authors: Lee K. M. 
Published: March 2011

ABSTRACTThe first experimental evidence of an isolated self-interstitial defect in an as-grown semiconductor is reported. An optically detected magnetic resonance spectrum observed in GaP [0] was identified as arising from a Ga selfinterstitial. The large isotropic hyperfine splittings (g = 2.003 (3), A(69Ga) = 741(5)×10−4 cm−1 and A(71Ga) -941[5]×10− 4 cm−1) revealed that a single Ga atom at a Td-symmetric site is the center of the defect. The interstitial nature is established by theoretical considerations. The spin dependent recombination process is attributed to a non-radiative donor-acceptor-pair process involving the Ga++ state which is in competition with a radiative (Odeg; - A° ) pair process and an electron capture process at O-donor.
Optically Detected Magnetic Resonance Studies of Complex Antisite-Related Defects in Bulk Lec GaP
Authors: Chen W. M. , Godlewski M. , Monemar B. , Gislason H. P. 
Published: March 2011

ABSTRACTA range of PGa antisite-related complex defects in LEC GaP:Cu, Li was observed with optically detected magnetic resonance. These isoelectronic defects are formed by a compensation of the PGa double donor by the CUGadouble acceptor on adjacent cation sites. T electronic structure of these defects is discussed, as well as their role in non-radiative recombination.
Ge Related Defect-Complex Induced Luminescence in InGaAsP
Authors: Arora B. M. , Chakravarty S. , Chandvankar S. S. , Rajalakshmi R. , Srivastava A. K. 
Published: March 2011

ABSTRACTGermanium doping of InGaAsP epitaxial layers grown by liquid phase epitaxy produces n type conduction with a net distribution coefficient KGe∼ 5×10-3. In addition, Ge doping introduces a broad band (∼0.2eV) of efficient luminescence which is red shifted with respect to the band edge. The intensity of this band grows with increasing Ge concentration. In all the samples, the integrated intensity of the broad band varies relatively less in the temperature range 15K to about 90K. At higher temperatures, the intensity falls exponentially with an activation energy of 0.05 - 0.07 eV. The emission spectra are compared with the configuration-coordinate model of the emission from a Ge related complex.
A Comparative Study of Different Rapid Annealing Techniques on Electrically Active Defects in Unimplanted Gallium Arsenide
Authors: Marrakchi G. , Guillot G. , Nouailhat A. 
Published: March 2011

ABSTRACTThe present paper describes the evolution of native defects and the introduction of new defects by transient annealing on unimplanted Bridgman (B) or Liquid Phase Epitaxy (LPE) Gallium Arsenide (GaAs). Three techniques covering all the timescales below those available with the conventional furnace annealing were used: Pulsed Electron Beam Annealing (PEBA), Continuous Wave Laser (CWLA) and Rapid Thermal Annealing (RTA). Electronic defects have been investigated by Deep Level Transient Spectroscopy (DLTS). The evolution of native defects and the introduction of new defects, are strongly dependent on the annealing technique. A significant decrease of EL2 concentration has been observed after PEBA, but it is not affected by CWLA or RTA under our annealing conditions. On the contrary, the other native defects EL6 and EL3 are completely annealed by RTA and PEBA. Furthermore, both DLTS spectra recorded after PEBA and RTA on the B substrates show introduction of new defects. However, CWLA does not affect the defects present in B GaAs, but an electron trap termed PL1 was introduced by this treatment in a thin oxide layer formed on the LPE grown GaAs.
Extended X-Ray Absorption Fine Structure Studies of Impurities in Semiconductors
Authors: Sette F. , Pearton S. J. , Poate J. M. , Rowe J. E. 
Published: March 2011

ABSTRACTWe discuss Extended X-ray Absorption Fine Structure (EXAFS) experiments on impurities in semiconductors. The local structure of the impurity site is determined for the first, second and third neighbor shells. These studies are carried out on absorption edges in the soft x-ray region using a novel fluorescence detection scheme which reveals improved detection sensitivity when compared with more standard electron Auger yield methods. The higher detection sensitivity allows structural studies at atomic densities as low as 1018 at/cm3 and this technique is used to study the local structure of P and S impurities in GaAs and of S in Alx Gal−x, As at concentrations of 1019–1020 at/cm3. The P atoms are substitutional on As sites, and a breathing relaxation of the P first shell Ga atoms is responsible for a P-Ga distance of 2.38Å, which is 0.07Å shorter than the As-Ga distance in GaAs(2.45Å). No detectable relaxation is observed in the P second and third atomic shells. In S-doped GaAs we find two different populations of S-Ga bonds with nearly equal intensity and both with S located on the As sub-lattice. These findings indicate two different configurations of substitutional S in GaAs. The coexistence of two similarly populated, charge compensating configurations is the first structural evidence which allows us to explain the observation that in n-doped GaAs the electrical activity of donors is lower than the atomic concentration. Finally, we present experimental results on S impurities in AlxGal−x, As (0.2<x<0.5). In this system, at the Al concentrations we studied, the S impurities are bound only to Al and not to Ga atoms. We report the formation of an extended complex which is discussed in connection with the structural identification of DX centers in these materials.