bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of free-carrier absorption to N-ZnSe materials characterization
Authors: Ruda H. E.
Published: July 2002

Quantum theory has been applied to calculations of free-carrier absorption in N-ZnSe (including all major scattering mechanisms and screening). The electron concentration n, dependence of the free-carrier absorption coefficient α, was calculated as a function of the ionized impurity concentration and the compensation ratio θ. An inherent limit to α, αinh, was determined at photon wavelengths, λ, of 3.3, 5, and 10 μm. At 10 μm, log αinh (cm−1)≂log n (cm−3)−15.9 for 1014≲n (cm−3)≲1017. A second experimental parameter, the derivative logarithmic absorption coefficient p, is shown to provide an unambiguous method for uniquely determining n and θ, when used in conjunction with α‖λ. The relation of n (cm−3)≂6.7×1015 (3.5 −p) α (cm−1) is proposed for λ=10 μm. Experimental data from the literature are analyzed in this scheme and values of n determined by Hall-effect measurements are shown to be in excellent agreement with theoretical predictions.
Low-temperature annealing of shallow arsenic-implanted layers
Authors: Young N. D. , Clegg J. B. , Maydell-Ondrusz E. A.
Published: July 2002

Silicon layers implanted with 10 keV arsenic have been characterized using the differential Hall effect, secondary-ion-mass spectrometry, and Rutherford backscattering. Arsenic has been implanted to doses up to 2×1015 cm−2 and the layers have been annealed for 15 min at temperatures in the range 600–900 °C. The maximum free-carrier concentration and sheet resistance obtainable are 2.8×1014 cm−2 and 320 Ω/⧠, respectively, for a dose of 1×1015 cm−2 annealed at 700 °C. There is evidence for both the loss of arsenic into a thin surface layer and the incomplete electrical activation of the arsenic remaining in the bulk. It is proposed that incomplete electrical activation is due to clustering in the amorphous phase during the solid-phase-epitaxial regrowth of the layer rather than clustering in the crystalline phase after the regrowth has occurred.
A two-temperature model of the inductively coupled rf plasma
Authors: Mostaghimi Javad , Proulx Pierre , Boulos Maher I.
Published: July 2002

A two-temperature model is proposed for the computation of the two-dimensional flow and temperature fields in a rf inductively coupled plasma torch. The model is applicable to monatomic gases. The results obtained for an argon plasma indicate that, while at atmospheric conditions, deviations from local thermodynamic equilibrium (LTE) are relatively small, the situation is different under reduced pressure conditions, where substantial deviations from LTE have been noted, particularly in the energy addition region.
Metalorganic vapor-phase-epitaxial growth of Fe-doped In0.53Ga0.47As
Authors: Tell B. , Koren U. , Miller B. I.
Published: July 2002

The electrical properties of Fe-doped In0.53Ga0.47As, grown by metalorganic chemical vapor deposition, are described. Fe concentrations in the 1017–1018 cm−3 range are readily obtained, resulting in electrical resistivities of 50–1000 Ω cm. Holes are the majority carrier, but the effective mobility can be predominantly due to minority electrons. From measurements of the temperature dependence of the resistivity and mobility, the Fe acceptor ionization energy of 0.35 eV is determined.
dc electroluminescence in copper-free Zns:Mn thin films. I. Local destructive breakdown and its dependence on preparation and test conditions
Authors: Blackmore J. M. , Cattell A. F. , Dexter K. F. , Kirton J. , Lloyd P.
Published: July 2002

The proportion of random localized destructive breakdown to stable electroluminescence has been varied continuously by adjusting (1) the recipe used to fabricate dc thin-film electroluminescent devices and (2) the conditions under which they have been tested. It has been shown that neither simple geometrical artifacts nor migration effects can be responsible for localized destructive breakdown. Rather, it has been established that the experiments require an explanation based on a fundamental tendency for dc thin-film electroluminescence to be associated with a current-controlled negative differential resistance which gives rise to filamentary and sometimes destructive current concentration. It is concluded that the existence and origins of such current-controlled negative differential resistance should be tested by theoretical and materials science studies.
Electron-hole interaction and high-field transport of photoexcited electrons in GaAs
Authors: Osman M. A. , Ferry D. K.
Published: July 2002

We use a theoretical ensemble Monte Carlo method to study the response of carriers photoexcited by a 1.55-eV laser pulse to applied electric fields (less than 5 kV/cm) for excited carrier densities between 1017 cm−3 and 1018 cm−3. It is found that the electron-hole interaction reduces the fraction of electrons that transfer to the upper valleys and reduces the velocity of the electrons. These effects are more significant at low electric fields and higher excitation levels. The energy of the holes rises initially due to the energy transfer from the hot electrons through the electron-hole interaction. This is also reflected in a higher velocity for the holes during the first picosecond.
The effects of In doping on the heteroepitaxial growth of ZnS on GaP substrates
Authors: Fuke Shunro , Araki Hitoshi , Kuwahara Kazuhiro , Imai Tetsuji
Published: July 2002

Single-crystal layers of ZnS have been grown on GaP substrates in a hydrogen transport system. In order to clarify the doping effects of In on the growth behavior, some In-doping experiments with various doping processes are performed. The reversal in the orientation dependence of the growth rate and the improvement of the crystallinity of the epitaxial layers are caused by the existence of In atoms and/or In compounds at the growing surface of ZnS. The In atoms and/or In compounds which exist at the interface between the GaP substrate and ZnS epitaxial layer are shown to have no significant effect on the growth behavior.
Evidence for EL6 (E
c− 0.35 eV) acting as a dominant recombination center in n-type horizontal Bridgman GaAs
Authors: Fang Zhao-Qiang , Schlesinger T. E. , Milnes A. G.
Published: July 2002

Horizontal Bridgman grown n-type GaAs is shown to contain two important electron traps EL6 (0.35 eV) and EL2 (0.80 eV) in the 1015 cm−3 concentration range. A heat treatment at 800 °C for 1 h results in the reduction of EL6 to about 1013 cm−3 to a depth of at least 10 μm and an increase in EL2 by an amount about equal to the reduction of EL6. Measurement of the minority-carrier (hole) diffusion lengths in this depth range by an electron beam induced current (EBIC) technique shows an inverse correlation with the concentration of the EL6 trap. The results may be explained if EL6 is assumed to be VGa-VAs, EL2 to be AsGa-VAs, and the interaction between the two traps to involve Asi.
Auger electron spectroscopy, transmission electron microscopy, and scanning electron microscopy studies of Nb/Al/Nb Josephson junction structures
Authors: Chang Chuan C. , Gurvitch M. , Hwang D. M. , Blonder C. W.
Published: July 2002

Al films deposited on Nb can be oxidized and used to make Josephson junction devices. We studied the structure of Al films deposited under ‘‘warm’’ (estimated to be near 200 °C) and ‘‘cold’’ (near room temperature) conditions because the cold films produced better Josephson junction devices. For the warm case, the Al film was composed of islands with open channels between them, which we attribute to a high mobility of the Al atoms that lowers the island nucleation density. The Nb surface was extremely flat, which we ascribe to the high surface atom mobility at the higher deposition temperature. The cold Al film was of uniform thickness which can be explained by a high island nucleation density. The cold Nb films had an undulating surface, caused by the lack of surface atom mobility during deposition. There was no evidence of Al-Nb interdiffusion, even after postdeposition heating to 300 °C. Auger spectroscopy, transmission electron microscopy, and scanning electron microscopy were needed to obtain these definitive conclusions.
From heavy fermion to mixed valence, a study of Ce(Pb1−xSnx)3
Authors: Lin C. L. , Crow J. E. , Schlottmann P. , Mihalisin T.
Published: July 2002

CePb3 has been shown to be a heavy-fermion antiferromagnetic system with a Neél temperature, TN=1.1 K, and CeSn3 is a mixed valent system with considerable  f-spd hybridization. Studies of pseudobinary alloys from CePb3 to CeSn3 provide an excellent opportunity to examine systematically the evolution of physical properties as the  f-spd hybridization increases and the heavy-fermion state is suppressed. Measurements of the temperature dependence of the resistivity, magnetic susceptibility, and specific heat for the pseudobinary alloy Ce(Pb1−xSnx)3 are presented and discussed. Some features obtained from this study are that, upon substitution of Sn for Pb in CePb3, the electronic specific-heat coefficient and low-temperature magnetic susceptibility display a monotonic variation with increasing x and TN is rapidly suppressed.
Domain structures in polycrystalline Tb0.27Dy0.73Fe2 (Terfenol) in the applied field region of optimum magnetoelastic properties
Authors: Branwood A. , Janio A. L. , Piercy A. R.
Published: July 2002

A Bitter colloid technique has been used to study field-induced domain changes in polycrystalline Tb0.27Dy0.73Fe2 (Terfenol) in the bias field region where the incremental strain and magnetomechanical coupling coefficients are known to maximize. The dominant feature of the structures in this critical field region was found to be the formation of stripelike domains with their long directions inclined at large angles to the applied field. One of a series of optical micrographs showing domain changes at increasing applied fields, and electron micrographs of the dried colloid showing finer details of these domains at chosen bias fields, are presented for grains whose orientations have been determined by x-ray methods. It was found that the majority of these domains were separated by 71° walls. Such an arrangement might be expected in view of the high magnetoelastic coefficients characteristic of this field region.
Electron avalanche injection on 10-nm dielectric films
Authors: Dori Leonello , Arienzo Maurizio , Nguyen Thao N. , Fischetti Massimo V. , Stein Kenneth J.
Published: July 2002

Uniform electron avalanche injection has been successfully performed on 10-nm SiO2 and on composite 8-nm SiO2+4-nm Si3N4 gate dielectrics. The films were grown on boron-implanted substrates to obtain the optimum surface impurity concentration for uniform injection. The electrical properties indicated high-quality and low-defect density dielectrics with no deleterious effects introduced by the ion implantation. A voltage flat-band Vfb shift and trap analysis were performed on both structures with and without post oxidation anneal, using metal or n-polysilicon gate. The results obtained have confirmed the trends found in thicker oxides and pointed out the presence of deep water-related centers. The composite structure, SiO2+Si3N4, showed high electron trapping due to two Coulombic centers normally invoked for Poole–Frenkel conduction in Si3N4. These centers are usually undetected by high-field injection experiments.
High-frequency limits of superconducting tunnel junction mixers
Authors: Winkler D. , Claeson T.
Published: July 2002

We have investigated high-frequency limits of superconducting quasiparticle mixers from experiments on Al/Al-oxide-In/Al (or Ag) tunnel junctions, and from calculations based on Tucker’s quantum theory of mixing (QTM). The small superconducting energy gap of Al enabled us to study mixer performance at around the junction gap frequency,  fg =(Δ1+Δ2)/h≊87 GHz, of superconductor-insulator-superconductor (SIS) mixers, and at twice the junction gap frequency for S-I-normal metal (SIN) mixers ( fg =Δ1/h) with available millimeter wave sources. Because of the low transition temperature of Al (Tc ≊1.3 K), a dilution refrigerator was used for providing temperatures below 1 K. The best mixer conversion efficiency was obtained for a low-resistance (∼34 Ω) six-junction array SIS mixer operated at  f/fg ≊1 (in this case 73 GHz). The coupled single sideband conversion gain (with no image rejection) was −13.8 dB and the available conversion gain was estimated to −8.4 dB. Complicating nonequilibrium phenomena made it difficult to compare the performance of these relatively high-current-density mixers to the QTM. However, good agreement between calculated and corresponding measured conversion efficiencies and dynamic resistance values was obtained for the low-current-density mixers. Noise due to switching between rf-induced Josephson steps and interference from Josephson mixing could be quenched by a magnetic field. Several high-frequency limits are considered in this paper (such as Josephson switching noise, nonequilibrium phenomena, pair breaking, and energy gap limitations). Our results indicate that submillimeter wave SIS mixer receivers are likely to perform well, at least up to their gap frequencies, i.e., the THz region for large gap superconductors. Our QTM calculations showed that conversion gain larger than unity should be possible up to twice the gap frequency. Above this frequency the conversion loss will increase rapidly.
Cross-sectional transmission electron microscope study of residual defects in BF+2 implanted (111) Si
Authors: Nieh C. W. , Chen L. J.
Published: July 2002

A combined cross-sectional and plain-view transmission electron microscope study of residual defects in 110-keV 5×1015/cm2 BF+2 -implanted (111) Si has been carried out. The samples were annealed isothermally in N2 ambient at 600–1100 °C with 100 °C increments. The distribution, density, and size of point defect clusters, twins, equiaxial loops, elongated loops, and bubbles were analyzed in detail. The origin and evolution of the residual defects are discussed.
Atomic model for the EL0 defect in GaAs
Authors: Wager J. F. , Van Vechten J. A.
Published: July 2002

We propose atomic models for the stable and metastable configurations of the bi-stable, oxygen-related defect in GaAs known as EL0. They consist of an O on As site donor as a nearest neighbor to a divacancy for the stable configuration and an O on Ga site acceptor between two As vacancies for the metastable configuration. We discuss analogies and distinctions between EL0 and EL2, another important bi-stable complex. We suggest that this complex is prominent in O-containing GaAs because divacancies migrate relatively rapidly and so are prone to formation of complexes.
A study of the oxidation of selected metal silicides
Authors: Frampton R. D. , Irene E. A. , d’Heurle F. M.
Published: July 2002

I n situ ellipsometry was used to investigate the oxidation behavior of a group of silicides, CoSi2, CrSi2, Ir3Si5, Ru2Si3, and WSi2, on single-crystal silicon substrates. These observations were complemented by ex situ ellipsometric measurements on these silicides, as well as on Mn11Si19, MoSi2, NiSi, NiSi2, and ReSi2. Refractive index measurements necessary for the oxide thickness calculations were made using ellipsometry on the bare silicide surfaces. Three regimes of oxidation behavior were identified: one group of silicides oxidized much faster than Si itself, CoSi2, CrSi2, NiSi, and NiSi2; another group was intermediate in oxidation rate between the fast group and Si at low temperature, typically comprising the refractory silicides MoSi2 and WSi2; the third group oxidized at about the same rate as Si and included the semiconducting silicides Ir3Si5, ReSi2, and Ru2Si3. The oxidation of Mn11Si19 led to an oxide containing a small amount of Mn. The oxidation rates of the silicides scale with both the reported carrier concentrations and the measured absorption index. Thus, the electronic properties of the silicides are thought to be responsible for the oxidation behavior. Buffered HF etch rates of the oxides grown on silicides indicate that the oxides grown on the rapidly oxidizing silicides are less dense than the oxides on the intermediate and slowly oxidizing silicides.
Diffusion of B and As from polycrystalline silicon during rapid optical annealing
Authors: Böhm H. J. , Wendt H. , Oppolzer H. , Masseli K. , Kassing R.
Published: July 2002

The diffusion of B and As from polycrystalline Si into single-crystal Si during rapid optical annealing (ROA) has been investigated. Samples were characterized by secondary ion mass spectrometry, transmission electron microscopy, and sheet resistance measurements. It is demonstrated that very shallow diffusion profiles in the single-crystal Si can be formed by ROA. At 1050 °C/5 s, for instance, a junction depth of ∼35 nm is obtained for As diffusion. The effect of polycrystalline Si/mono-Si interface treatment on the dopant diffusion and the polycrystalline Si grain structure will be discussed.
Transient photoconductivity measurements in semi-insulating GaAs. II. A digital approach
Authors: Abele J. C. , Kremer R. E. , Blakemore J. S.
Published: July 2002

We describe an experimental setup designed to study photoconductive transients in semi-insulating materials. The method, known as photoinduced transient spectroscopy, is based on a digital signal-averaging technique. Although this digital method eliminates or reduces many of the experimental problems encountered when using an analog approach, several new problems arise. The method is described, and the difficulties are illustrated using data obtained from both Cr-doped and nominally undoped samples of GaAs.
Dislocation structure in InxGa1−xAs/GaAs strained-layer superlattices
Authors: Rajan K. , Devine R. , Moore W. T. , Maigné P.
Published: July 2002

The dislocation structure in InGaAs/GaAs strained-layer superlattices has been characterized by transmission electron microscopy. It is shown that most of the dislocations are confined to the buffer/strained-layer superlattice interface. We have also found that the strained-layer interface can be an effective barrier to dislocation propagation. Extended dislocations, which are potentially electrically active defects, are shown to exist in the strained-layer superlattice.
Effects of Si thin interfacial layer on W/GaAs contacts
Authors: Kuriyama Youichi , Ohfuji Shin-ichi , Nagano Jin
Published: July 2002

Chemical reactions and Schottky-barrier characteristics of W(200-nm-thick)/Si(0–2.5-nm)/GaAs contacts annealed at 800 °C have been investigated. The Si interfacial layer and the W film were sputter deposited successively on chemically etched GaAs substrates to fabricate Schottky-barrier diodes. The W/Si/GaAs diodes show nearly the same Schottky-barrier characteristics as tungsten-silicide (WSi0.6)/GaAs diodes. By using secondary ion mass spectrometry, the Si layer is found to suppress Ga and As atom diffusion from GaAs substrates into W films during annealing at 800 °C for 60 min. A reduction of natively oxidized GaAs surfaces is also observed at the initial stage of Si layer deposition by x-ray photoemission spectroscopy. These results suggest that the Si layer eliminates native oxides from GaAs surfaces, resulting in tungsten-silicide/GaAs intimate contact formation at the interface, and the Si stuffs diffusion paths of Ga and As atoms at W grain boundaries with W-Si-O ternary compounds.
An electron-spin resonance study of the structure of plasma-deposited silicon-oxynitride films
Authors: Denisse C. M. M. , Janssen J. F. M. , Habraken F. H. P. M. , Van der Weg W. F. , Schuivens E. G. P.
Published: July 2002

We have measured electron-spin resonance spectra of silicon-oxynitride layers grown by plasma-enhanced chemical vapor deposition from gas mixtures of SiH4, N2O, and NH3. The analyses were performed on untreated, thermally annealed, and gamma irradiated samples. A relatively small spin density (about 1017 cm−3) is found for the as-deposited layers. Since the resonances remain weak upon annealing, gamma irradiation was performed in order to acquire more structural information on the silicon-oxynitride network. The evolution of the spin density upon annealing is discussed in relation to the hydrogen release during annealing. In the as-deposited and annealed samples, g values were found close to 2.0055. This strongly suggests the presence of silicon clusters in the material. Spin densities remain low upon annealing unless we anneal at temperatures as high as 1000 °C. For these temperatures, smaller g values are observed. Irradiation with gamma rays induces similar signals except for oxygen-rich samples. These show a narrow line at a g value of about 2.001, which can be ascribed to E′ centers. The intensity of this signal falls rapidly with decreasing oxygen content, which implies that these materials are not made up of a mixture of a silicon-nitride and a silicon-oxide phase.
The first stages of oxidation of a-Si studied with Auger electron spectroscopy
Authors: Vidal R. , Koropecki R. , Arce R. , Ferrón J.
Published: July 2002

We have studied the first stages of low-pressure oxidation of amorphous silicon using Auger electron spectroscopy. The application of the principal component analysis to the Si L2,3 core-valence-valence transition spectra, acquired during the oxidation, allows us for the interpretation of the oxidation kinetics of the a-Si. Using the target transformation method we have isolated the Auger spectra of the components present during the oxidation process. We observe an intermediate state in the Si-SiO2 interface formed during the oxidation. This state was attributed to a SiOx-type compound.
Variations of electron traps in bulk n-GaAs by rapid thermal processing
Authors: Katayama Masayuki , Usami Akira , Wada Takao , Tokuda Yutaka
Published: July 2002

Rapid thermal processing (RTP) using halogen lamps for liquid encapsulated Czochralski grown GaAs doped with Si has been studied by deep-level transient spectroscopy, capacitance-voltage, and photoluminescence measurements. RTP is performed at 700, 800, and 900 °C for 6 s with and without SiO2 encapsulation. Three electron traps ED1(Ec −0.26 eV), ED2(Ec −0.49 eV), and ED3(Ec −0.55 eV) are produced depending on RTP conditions. The trap ED1 is observed in all RTP samples, and its depth profiles vary with RTP conditions. The decrease of the shallow donor concentration occurs for RTP samples above 800 °C, especially for those without encapsulation. It is thought that these results, which are peculiar to the RTP method, are related to the production of As interstitials and As vacancies by the large thermal stress induced by the rapid heating for RTP. The decrease of the concentration of trap EL2(Ec −0.81 eV) is not observed with RTP as reported in the furnace processing. This is due to the effect of the short-time processing of RTP.
Formation of shallow n+p junctions
Authors: Naem A. A. , Calder I. D.
Published: July 2002

The effects of preamorphization and rapid thermal annealing (RTA) on the formation of shallow arsenic junctions have been investigated. Single-crystal silicon substrates were preamorphized with a Si+ implant (3.0×1015 ions/cm2 at 60 keV) followed by an As+ implant (1.0×1015 to 1.0×1016 ions/cm2 at 50 keV) through a 200-Å oxide cap. As+implantation into single-crystal silicon was also investigated. RTA and reference furnace anneals were carried out to recrystallize the amorphous layers into single crystals and to activate the arsenic implants. Experimental results have been obtained for amorphous layer characteristics, residual damage, dopant profiles, junction depth, sheet resistance, and carrier concentration. Measurements were made by spreading resistance probe (SRP) and secondary ion mass spectrometry (SIMS) profiling, Rutherford backscattering spectrometry (RBS), and transmission electron microscopy (TEM); a limited amount of junction leakage data was also obtained. Arsenic depth profiles as measured by SIMS, RBS, and SRP are compared. The agreement between the three profiling techniques is fair to good. RTA resulted in junctions with crystal quality and dopant activation similar to those of furnace annealed junctions with less impurity profile broadening. Preamorphization did not result in a significant reduction in the junction depth and inhibited complete removal of extended defects. Two criteria for an acceptable anneal were considered; damage removal was not considered to be as significant as leakage current reduction. An optimum RTA cycle was determined to be 1050 °C for 20 s.
Dynamical conversion of optical modes in garnet films induced by ferrimagnetic resonance
Authors: Neite B. , Dötsch H.
Published: July 2002

It is demonstrated that ferrimagnetic resonance can be applied to induce a dynamical conversion of optical modes in a magnetic garnet film. The fundamental and first-harmonic Fourier components of the converted mode are measured as a function of frequency and bias field; a dynamical conversion efficiency of 2% is obtained. The amplitude of the first harmonic depends very critically on the orientation of the magnetization with respect to the film normal. The results are confirmed by calculations on the basis of Faraday rotation and Cotton–Mouton effect.
Electron self-trapping in SiO2
Authors: Aslam M.
Published: July 2002

Electron trapping and detrapping behavior of SiO2 has been studied at different temperatures by applying avalanche injection technique to metal oxide semiconductor capacitors. Experimental evidence is presented for the transfer of electrons initially captured at 100 K by shallow centers with σ≂10−16 cm2 to the deep centers with σ≂10−19 cm2. The trapping sites with σ<10−16 cm2 that are located near Si-SiO2 interface exhibit the highest probability of charge transfer. The centers with σ>10−16 cm2 show no transfer of charge. It is proposed that the electrons localized at 100 K by the centers with σ≤10−16 cm2 undergo a self-trapping process that is triggered by a lattice relaxation. The lattice relaxation seems to be encouraged by the strain in the interfacial region.
A magnetic multipole reactor for high-flux reactive-ion etching
Authors: Kuypers A. D. , Granneman E. H. A. , Hopman H. J.
Published: July 2002

A 13.56-MHz rf discharge has been combined with two kinds of magnetic field. A multipole field, generated by permanent magnets in the surrounding walls, is used to confine the plasma. Superimposed on this is a variable magnetic field parallel to the substrate surface, which is shown to give a considerable increase in plasma density and reduction of electrode self-bias. Etch rates of SiO2 in a CF4 discharge of 5000 Å/min at mTorr pressures are presented.
Preparation and characteristics of ZnS thin films by intense pulsed ion beam
Authors: Shimotori Yutaka , Yokoyama Meiso , Isobe Hironobu , Harada Shigetoshi , Masugata Katsumi , Yatsui Kiyoshi
Published: July 2002

A new deposition system has been developed for the preparation of ZnS thin films by an intense pulsed ion beam (1 MeV, 80 ns). The maximum beam-power density of ∼5 GW/cm2 is concentrated on ZnS, so that a high-temperature plasma is easily produced. The plasma composed of Zn and S expands to be deposited onto a substrate kept at room temperature. Clear evidence has been obtained on the production of polycrystalline ZnS thin films with hexagonal structure. The deposition rate is estimated to be ∼108 Å/s, which is several orders of magnitude higher than with any other method.
Annealing behavior of Si implanted InP
Authors: Kräutle Herbert
Published: July 2002

Rapid thermal annealing with a lamp furnace and conventional furnace annealing have been applied to InP 〈100〉 implanted with Si ions of 40 and 350 keV and doses of 1013–1015 cm−2. After examination of different capping layers, phosphorus silica glass was chosen. Sheet carrier concentration, Hall mobility, and carrier-concentration depth profiles were measured. A time of 10 s at 800 °C is sufficient to activate the dopants. Rutherford backscattering channeling measurements show the damage and the recrystallization due to different annealing procedures. To optimize the annealing of the damage, a relatively long time for the heat treatment is necessary which, however, results in enhanced diffusion of the dopants.
Abnormal behavior of midgap electron trap in HB-GaAs during thermal annealing
Authors: Min Suk-Ki , Kim Eun Kyu , Cho Hoon Young
Published: July 2002

The behavior of the EL2 family in horizontal Bridgman-(HB) grown GaAs by two thermal annealing methods, furnace annealing and rapid thermal annealing, was studied through deep level transient spectroscopy (DLTS) measurements, and a similar behavior of another group of electron traps was observed. As the annealing time is increased, the EL2 trap (Ec-0.81 eV) is transformed to the new trap, EX2 (Ec-0.73 eV), and finally to the other new trap, EX1 (Ec-0.86 eV). Also the EL6 group (Ec-0.18, 0.22, 0.27, and 0.35 eV) varied similarly to the EL2 family as a trap (Ec-0.27 eV) is transformed to the first trap (Ec-0.18 eV) and then the second trap (Ec-0.22 eV). This result revealed that the EL2 family is related to the EL6 group. From the study of photocapacitance quenching, the existence of metastable states of the EL2 family is identified. These results suggest that the atomic structure of the EL2 trap may be an arsenic antisite with an interstitial arsenic and a double vacancy, such as VAsAsIVGaAsGa or its complex.
Magnetoresistance of very thin cobalt-gold multilayers with perpendicular anisotropy
Authors: Dupas C. , Renard J. P. , Seiden J. , Vélu E. , Renard D.
Published: July 2002

We report magnetoresistance (MR) measurements on Au/Co/Au sandwiches and Au/Co/Au multilayers, deposited on polished glass substrates in ultrahigh vacuum, with Co thickness ranging between 3 and 30 Å. The experiments were performed at room temperature in the field range 0–0.8 T and at low temperature 1.3–4.2 K in the field range 0–5 T for different field orientations with respect to the film and to the current. For Co thickness below 11 Å, the experimental data are consistent with an easy axis perpendicular to the film, in agreement with previous ferromagnetic resonance and magnetization measurements. From the hysteretic behavior of the MR, coercive fields of a few 102 Oe at room temperature are observed. In Co bilayers, the MR is enhanced with respect to the MR of simple sandwiches and indicates a square hysteresis loop. The abnormally large MR of the ultrathin Co films is attributed to a Co/Au interface resistance related to walls between Co domains with alternating perpendicular magnetization.
Characteristics of electron traps in Si-implanted and rapidly thermal-annealed GaAs
Authors: Kitagawa Akio , Usami Akira , Wada Takao , Tokuda Yutaka
Published: July 2002

Rapid thermal annealing (RTA) using halogen lamps for Si-implanted (250-keV, 2×1013 cm−2 dose) semi-insulating liquid-encapsulated Czochralski GaAs has been investigated by deep level transient spectroscopy. RTA has been performed at 700, 800 and 900 °C for 6 s with SiO2 encapsulation. For comparison, conventional furnace annealing (FA) has also been performed at 800 °C for 20 min. In the RTA samples at 700 °C, three electron traps NI1 (Ec−0.53 eV), NI4 (Ec−0.63 eV), and EL2 (Ec−0.78 eV) are observed on the Cr-doped substrate, while the traps NI1, EL2, and NI3 (Ec−0.47 eV) are observed on the undoped substrate. In RTA samples above 800 °C, the electron trap NI2 (Ec−0.55 eV) or EL2 is dominant and traps NI1, NI3, and NI4 are not detected. It is possible that three traps NI1, NI3, and NI4 are residual defects produced by Si implantation. The low concentration of the trap EL2 in FA samples is due to the out-diffusion of it. This phenomenon can be related with the change of the stoichiometry in the implanted layer by the formation of the transition region at the SiO2 /GaAs interface during FA. The notable spatial variation of the trap NI2 is observed across the wafer. On the other hand, the peculiar spatial distribution of the trap EL2 is not observed across the RTA sample. Furthermore, the trap EL2 concentration does not depend on RTA temperatures. It is possible that the spatial distribution of the trap EL2 across the RTA sample is changed by Si implantation and RTA.
Correlation between electrical and compositional properties of SiO2-InSb interfaces
Authors: Avigal Y. , Bregman J. , Shapira Yoram
Published: July 2002

We have studied interfaces of n-InSb with SiO2 films, obtained by low-temperature chemical vapor deposition, using capacitance-voltage measurements and Auger electron spectroscopy (AES). Improvements of electrical properties of MOS capacitors based on this system were sought by various pre- and post-treatments. The results show that a methanol pre-treatment causes significant improvements in the flat-band voltage (VFB) of metal-oxide-semiconductor capacitors based on this system. In addition, thermal post-annealing in oxidizing atmospheres also improved VFB. AES reveals that at the SiO2-InSb interface there is a native oxide interlayer, the width of which was found to be reduced by a factor of 2–3 due to the specified treatments. Therefore, we attribute the VFB improvement to the reduction in the density of charges and traps due to the narrowing of the interfacial native oxide, in agreement with other recent results.
Stoichiometric structures of defects in high-purity GaAs grown by the liquid encapsulated Czochralski method
Authors: Morrow Richard A.
Published: July 2002

We analyze some existing data obtained on a GaAs sample grown by the liquid encapsulated Czochralski (LEC) method from a near-stoichiometric melt after the sample was cycled through various thermal processes. By using the constraint of constant deviation from stoichiometry we are led to suggest that the defects observed or inferred to exist in the sample have the following properties: (1) the acceptor associated with the 1.45-eV photoluminescence signal has the stoichiometric structure of GaAs if doubly charged or of VGaGaAs if singly charged; (2) the (presumed) donor at Ec−0.134 eV has the stoichiometric structure of VAs; (3) another (inferred) acceptor has the stoichiometric structure of VGa; and (4) the very shallow donor at Ec−0.003 eV is the precursor of EL2 and becomes EL2 upon reaction with VGa or its stoichiometric equivalent.
Linear electro-optic effect: Comparison of GaAs/AlGaAs multi-quantum-well heterostructures with an AlGaAs solid solution at 1.1523 μm
Authors: Glick M. , Reinhart F. K. , Martin D.
Published: July 2002

We report the first comparison of electro-optic studies in multi-quantum-well structures of different well widths (66 and 122 Å thick) and an AlGaAs solid solution. We find increases in the electro-optic coefficient due to effects of the quantum-well fall within the range of experimental error. We show that far from the band gap the electro-optic coefficient, r41, for the solid solution can be approximated by averaging the results for the binary compounds GaP and GaAs. We argue that our results can be understood in the framework of an extended oscillator model.
A simulation of keV electron scatterings in a charged-up specimen
Authors: Kotera M. , Suga H.
Published: July 2002

Supposing that an insulator is charged-up negatively by an accumulation of incident primary electrons, we study how much the subsequent incident electron is influenced by the charge in the specimen. We introduce a new Monte Carlo simulation model of electron scattering in a solid taking into account an electric field around the simulated electron. In a present study the incident electron energy is 20 keV, and the insulator is a poly-methyl-methacrylate wafer of 1 mm in thickness. This paper clarifies the changes in some physical quantities, e.g., the backscattering coefficient, energy deposition, etc. due to the specimen charging during an electron beam irradiation.
Mechanism for chemical-vapor deposition of tungsten on silicon from tungsten hexafluoride
Authors: Yarmoff Jory A. , McFeely F. Read
Published: July 2002

The mechanism for the growth of tungsten films on silicon substrates with the use of low-pressure chemical-vapor deposition from WF6 was studied with soft-x-ray photoemission by growing films in situ. The dissociative chemisorption of WF6 on Si(111) was found to be complete, even at room temperature. The reaction is self-poisoning at room temperature, however, as the fluorine liberated from WF6 ties up the active Si sites responsible for the dissociation. The mechanism for continued growth of tungsten films at elevated temperature was determined to proceed via Si diffusion through the layer towards the surface. Post-fluorination of these films via XeF2 was employed as a means for illustrating their morphology.
The identification of dark-line defects in AlGaAs/InGaAs/GaAs heterostructures
Authors: Fitzgerald E. A. , Ashizawa Y. , Eastman L. F. , Ast D. G.
Published: July 2002

We have investigated the correlation between the structure of and the nonradiative recombination at defects in AlGaAs/InGaAs/GaAs heterostructures using scanning cathodoluminescence (CL) and transmission electron microscopy (TEM). It is shown that the dark-line defects seen in scanning CL images do not always correspond to individual misfit dislocations even for relatively low mismatched epilayers. CL and TEM images from the same area reveal that there are structures which do correlate to the dark lines seen in CL. The density of dislocations at the interface determines which structure dominates the CL image. At very low misfit, the dark lines correspond to single 60° or edge dislocations, whereas at higher misfit the dark lines correspond to groups of dislocations. Contrary to previous studies in GaAlAsP/GaAlAs semiconductor heterostructures [J. Microsc. 118, 255 (1980)], we have found that edge dislocations at AlGaAs/InGaAs and InGaAs/GaAs interfaces are higher nonradiative recombination sites than 60° dislocations. TEM micrographs show that edge dislocations form more readily along one 〈110〉 direction, possibly explaining differences in residual elastic strain measurements along different 〈110〉 directions.
Growth and structure of aluminum films on (001) silicon carbide
Authors: Bermudez V. M.
Published: July 2002

The formation and the physical and electronic structure of the interface between Al and SiC films, grown epitaxially on Si(001), are studied using x-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), and energy-loss spectra (ELS). Zr M-zeta excitation (hν=151.4 eV) is employed to obtain high surface sensitivity in the Si and Al 2p and valence-band photoemission. The first few monolayers of Al grow as layers, with Al island formation at higher coverage. Al-Si interaction is apparent as a shift of the Al 2p (Si 2p) to higher (lower) binding energy (BE) for θ≤1. A Schottky barrier height of ≊1.4 eV is estimated. At higher θ the Al 2p assumes the BE and shape characteristic of bulk Al, and the Si 2p shows satellite structure to lower BE suggesting both Si bonded to Al and C as well as Si interacting mainly with Al. Annealing (350≤T≤1050 °C) leads to a reduction in Al coverage and reversal of the trends observed during sequential deposition. Before annealing LEED shows only a weak (1×1) pattern. Annealing at successively higher temperatures leads to a sharper (1×1), followed by two-domain (4×1) and two-domain c(8×2) patterns. No clear indication of Al carbide formation is found in Auger electron spectra or in the Al 2p XPS unless the SiC, prior to Al deposition, is first treated at high temperature to generate a C-rich surface.
Stresses in sputtered Ti-Si multilayers and polycrystalline silicide films
Authors: Wessels P. J. J. , Jongste J. F. , Janssen G. C. A. M. , Mulder A. L. , Radelaar S. , Loopstra O. B.
Published: July 2002

Titanium silicon multilayers have been produced by alternating sputter deposition. The stress in the as-deposited layers is a function of the period of the multilayer structure. The multilayers were subsequently annealed to form silicide films. From stress and strain measurements on these films Poisson’s ratio is determined. After annealing, the films exhibit a tensile stress which can be attributed to the difference in thermal expansion coefficient between substrate and silicide film.
Injection currents in insulators: Exact results
Authors: Tannous C. , Yelon A.
Published: July 2002

We present an exact solution for a single-carrier injection current in a perfect insulator with arbitrary field at the injecting boundary.
Magnetic structure and dynamics anomalies in ‘‘reentrant’’ spin glasses (invited)
Authors: Hennion M. , Hennion B. , Mirebeau I. , Lequien S. , Hippert F.
Published: July 2002

Neutron studies performed at zero field and in applied field on the reentrant spin glasses Ni1−xMnx and (Fe1−xMnx) 75P16B6Al3 reveal new features both in the static and in the dynamic correlations. The small-angle scattering shows a maximum at a finite qmax value in applied field. High-energy resolution measurements show that the stiffness constant of the spin waves has a still more surprising temperature dependence than first expected: as the temperature decreases it goes through a minimum and then increases further in the lowest-temperature range. We report the evolution of these features as a function of field, temperature, and concentration. qmax varies linearly with (H)1/2 with a slope which is related to the stiffness constant D of the spin waves. The dynamic anomalies are also seen in a field which saturates the magnetization.
Magnetic properties of rapidly quenched and annealed Fe10RTi and related alloys
Authors: Zhao Z. R. , Ren Y. G. , Aylesworth K. D. , Sellmyer D. J. , Singleton E. , Strzeszewski J. , Hadjipanayis G. C.
Published: July 2002

Magnetic measurements are reported for iron-rich ternary alloys with the following compositions: Fe10NdxDy1−xTi (0≤x≤1), Fe10SmM (M=Ti, V, and Mo), and Fe10RV (R=Y, Gd, and Dy). The samples were prepared by splat cooling or melt spinning and selected samples were heat treated. The results of x-ray diffraction, electron microscopy, and thermomagnetic measurements on the Fe10NdxDy1−xTi series are presented and indicate that the rapidly quenched alloys are nearly single phase and become multiphase upon heating. Magnetic measurements on the other two series show that the substitution of V for Ti increases the saturation magnetization.
Magnetic properties, anisotropy, and microstructure of sputtered rare-earth iron multilayers
Authors: Shan Z. S. , Nafis S. , Aylesworth K. D. , Sellmyer D. J.
Published: July 2002

A study of compositionally modulated magnetic films of the form Fe/RE, particularly for RE=Nd and Dy, has been performed by vibrating sample magnetometry, ac susceptibility and x-ray diffraction. The relationship between the magnetic properties and the layer thickness was studied systematically for X-Å Fe/Y-Å Dy, as the layer thicknesses X and Y were varied from 1.8 to 20 Å. The ranges of layer thicknesses required for perpendicular anisotropy were determined. The interface and volume anisotropy energies were estimated for X-Å Fe/Y-Å Nd and the differences in the magnetic properties between X-Å Fe/7-Å Dy and X-Å Fe/7-Å Nd are discussed.
Electronic properties of UNi(Al,Ga)
Authors: Sechovsky V. , Maletta H. , Havela L. , Veenhuizen P. A. , de Boer F. R.
Published: July 2002

The transition from itinerant antiferromagnetic behavior in UNiAl to ferromagnetism in UNiGa was studied by means of magnetic and specific-heat measurements on the pseudoternary series UNi(Al,Ga). The results are discussed in terms of a trend to increasing localization of the 5f electrons when proceeding to higher Ga concentrations.
Torque analysis of the perpendicular magnetic anisotropy in Co-Cr films
Authors: Ishibashi K. , Uchiyama Y. , Hwang U. , Suzuki T.
Published: July 2002

The tilt angle of the c axis from the film normal in Co-Cr flexible media fabricated by continuous sputter deposition is determined by analyzing torque curves, and is compared with that obtained by x-ray diffraction. A discussion is given concerning the perpendicular anisotropy constant obtained from torque curves with and without considering such a tilt angle of the c axis.
Radiation damage and annealing in graphite implanted with H+2 and Mo+
Authors: Roth J. , Zuhr R. A. , Withrow S. P. , Eatherly W. P.
Published: July 2002

Radiation damage due to H+2 and Mo+ implantation into hot-worked pyrolytic graphite and into single-crystal graphite flakes has been studied using 1-MeV 4He+ ion channeling. The implant energies used, 35 keV for H+2 and 120 keV for Mo+, yielded ranges of about 1600 and 600 Å, respectively. For H2 implantation, a partially crystalline surface layer remains after a fluence of 2×1016 H/cm2; this layer is completely disordered at 2×1017 H/cm2. At higher hydrogen fluences a surface layer exfoliates. For Mo implantation the disorder introduced at a fluence of 5×1014 Mo/cm2 is sufficient to prevent channeling throughout the range. For both implant species, complete recrystallization of samples disordered up to the surface occurs for annealing only at temperatures above 2800 K. If a surface layer remains crystalline after implantation, recrystallization proceeds both from the bulk and from the surface, and crystallinity is restored at 2300 K. While hydrogen is known to be released at temperatures between 1100 and 1500 K, Mo remains within its original range distribution up to the temperature of complete recrystallization. At a temperature of 2300 K an ordering of the implanted Mo atoms with respect to the c axis is observed, indicating short-range migration within the range distribution. At 2800 K no more Mo could be found in the analyzed surface layer.
Implanted boron depth profiles in the AZ111 photoresist
Authors: Guimarães R. B. , Amaral L. , Behar M. , Fichtner P. F. P. , Zawislak F. C. , Fink D.
Published: July 2002

The isotope 10B has been implanted into the photoresist AZ111 in the 30–150 keV energy range. The corresponding depth profiles have been analyzed using the 10B(n,α)7Li reaction. At 60 keV, the profile changes from a regular shape to one with an additional tail directed towards the surface. Despite the nonregular shape of the ion distributions, it is possible to extract the characteristic range parameters such as projected range Rp, most probable range R̂, and full width at half-maximum. Good agreement is found between the experimental results and the calculations by Ziegler, Biersack, and Littmark (ZBL). It is also shown that the tail distribution follows closely the ZBL calculated ionization profiles. A tentative explanation of this behavior is given.
Characterization of Schottky barrier diodes by means of modulation technique
Authors: Kunze U. , Kowalsky W.
Published: July 2002

On the basis of the ac modulation technique a novel method is developed, which permits the extraction of the key parameters of Schottky diodes, i.e., the ideality factor, the barrier height, and the series resistance. These properties can be derived at any forward bias voltage from the current-voltage characteristic and its first and second derivative. Limitations to the method arise mainly from the voltage dependence of the effective barrier height, as can be shown by a model calculation. Applicability and exactness are demonstrated by experimental investigations of Ti/n-Si diodes with high series resistance, Yb/n-Si junctions, and Ti contacts on n-type InP, In0.73Ga0.27As0.64P0.36, and In0.53Ga0.47As.