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30 Sep 1996

Volume 69, Issue 14, pp. 1991-2139

Page 2 of 3 Pages Previous Page Next Page | Jump to Page

Real‐time assessment of overlayer removal on GaN, AlN, and AlGaN surfaces using spectroscopic ellipsometry

N. V. Edwards, M. D. Bremser, T. W. Weeks, R. S. Kern, R. F. Davis, and D. E. Aspnes

Appl. Phys. Lett. 69, 2065 (1996); http://dx.doi.org/10.1063/1.116881 (3 pages) | Cited 31 times

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Spectroscopic ellipsometry was used to assess the preparation of smooth and abrupt GaN, AlN, and AlGaN surfaces by wet chemical treatments in real time. About 20–50 Å of overlayer typically can be removed from air‐exposed samples. © 1996 American Institute of Physics.
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07.60.Fs Polarimeters and ellipsometers
81.65.Cf Surface cleaning, etching, patterning
81.05.Ea III-V semiconductors

Realization of optically pumped second‐order GaInN‐distributed‐feedback lasers

R. Hofmann, H.‐P. Gauggel, U. A. Griesinger, H. Gräbeldinger, F. Adler, P. Ernst, H. Bolay, V. Härle, F. Scholz, H. Schweizer, and M. H. Pilkuhn

Appl. Phys. Lett. 69, 2068 (1996); http://dx.doi.org/10.1063/1.116882 (3 pages) | Cited 21 times

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Room temperature distributed‐feedback (DFB) laser operation is demonstrated with emission wavelengths ranging from 389 to 399 nm. Second‐order DFB gratings were defined by electron beam lithography and reactive ion etching in the top GaN barrier layer of a GaInN/GaN double heterostructure grown by metalorganic vapor phase epitaxy. Our data allow a precise determination of the effective refractive index neff(λ) over the whole emission range. neff(λ) is compared with previously published values for GaN and GaInN. © 1996 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
78.45.+h Stimulated emission
78.66.Fd III-V semiconductors

Nitridation of sapphire. Effect on the optical properties of GaN epitaxial overlayers

N. Grandjean, J. Massies, and M. Leroux

Appl. Phys. Lett. 69, 2071 (1996); http://dx.doi.org/10.1063/1.116883 (3 pages) | Cited 80 times

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GaN layers were grown by gas‐source molecular beam epitaxy on sapphire substrates using ammonia as a nitrogen source. The nitridation of an Al2O3 surface prior to the GaN growth was followed in situ by reflection high‐energy electron diffraction. A strong variation of the surface lattice parameter was observed corresponding to the formation of an AlN relaxed layer. The nucleation of GaN on such a nitridated surface is facilitated, as checked by atomic force microscopy. Optimization of the nitridation procedure is achieved by investigating the photoluminescence properties of GaN thin films grown for different nitridation times. It is found that the band‐edge and the yellow‐band luminescences are strongly dependent on the nitridated starting surface. Finally, the optimized nitridation process is used to grow high‐quality GaN epitaxial layers. © 1996 American Institute of Physics.
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71.55.Eq III-V semiconductors
78.66.Fd III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)

Electric field dependent intersubband optical transitions in a ZnCdSe–ZnSe superlattice

Z. P. Guan and T. Kobayashi

Appl. Phys. Lett. 69, 2074 (1996); http://dx.doi.org/10.1063/1.116884 (3 pages) | Cited 1 time

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The polarization dependence of the excitonic transition in ZnSe‐Zn0.8Cd0.2Se superlattices was studied by low‐field electroreflection spectroscopy. A new peak observed in the lower energy side of the n=2 heavy‐hole exciton E2hh at room temperature is attributed to the forbidden transition in zero field from the n=2 heavy‐hole state to the n=1 electron state. This reflection change is found to be polarization dependent. © 1996 American Institute of Physics.
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78.20.Jq Electro-optical effects
78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors

High efficiency and fast modulation of Er‐doped light emitting Si diodes

S. Coffa, G. Franzò, and F. Priolo

Appl. Phys. Lett. 69, 2077 (1996); http://dx.doi.org/10.1063/1.116885 (3 pages) | Cited 56 times

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We demonstrate that the electrical excitation of Er ions incorporated within the depletion layer of a p+−n+ Si diode allows one to simultaneously obtain efficient pumping of rare earth ions and a fast turnoff time of the electroluminescence signal. In fact it is found that during pumping, under reverse bias at the breakdown, a high internal quantum efficiency (10−4) can be achieved since the Er ions are excited with a cross section of 6×10−17 cm2 and exhibit a decay lifetime of 100 μs at room temperature. On the other hand, when the diode is turned off, the electroluminescence signal dies off in less than 10 μs (a limit set by the time response of the adopted detector). These results are explained by observing that fast nonradiative decay of the excited Er ions can occur by Auger transfer of the energy to a free electron or to an electron bound to an Er‐related level in the bandgap. These processes are inhibited within the depletion layer and only set in when, at the turnoff, the excited Er ions are suddenly embedded within the heavily doped (∼1019/cm3) neutral region of the diode. © 1996 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
61.72.uf Ge and Si

Influence of the buffer layers on the morphology and the transport properties in InAs/(Al,Ga)Sb quantum wells grown by molecular beam epitaxy

H.‐R. Blank, M. Thomas, K. C. Wong, and H. Kroemer

Appl. Phys. Lett. 69, 2080 (1996); http://dx.doi.org/10.1063/1.116886 (3 pages) | Cited 24 times

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The growth of modulation‐doped InAs/(Al,Ga)Sb quantum wells on GaAs substrates employing molecular beam epitaxy requires care in the nucleation and the use of buffer layers to achieve high quality material. Despite a 7% lattice mismatch between the substrate and the active layers, fully relaxed epitaxial growth can be accomplished, and quantum wells with electron sheet concentrations of 7×1012 cm−2 having low‐temperature mobilities as high as 300 000 cm2/V s have been routinely fabricated recently in our laboratory. In the present work the combination of atomic force microscopy and van der Pauw measurements is used to investigate and explain the strong influence of the buffer layers on the morphology in the quantum well that is shown to be responsible for the great differences in the observed low‐temperature mobilities. © 1996 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
73.61.Ey III-V semiconductors

Er doping of AlN during growth by metalorganic molecular beam epitaxy

J. D. MacKenzie, C. R. Abernathy, S. J. Pearton, U. Hömmerich, X. Wu, R. N. Schwartz, R. G. Wilson, and J. M. Zavada

Appl. Phys. Lett. 69, 2083 (1996); http://dx.doi.org/10.1063/1.116887 (3 pages) | Cited 36 times

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The doping of AlN during growth by metalorganic molecular beam epitaxy with an Er effusion source has resulted in AlN:Er films exhibiting strong room‐temperature 1.54 μm photoluminescence (PL). The luminescence detected in the AlN:Er grown during this study was orders of magnitude greater in intensity than that from ion‐implanted samples and represents the first demonstration of strong emission from rare‐earth doped, epitaxial group III nitrides. Secondary ion mass spectroscopy was used to verify a dynamic range for this doping technique of 3×1017–2×1021 Er cm−3 with varying effusion cell temperature. The effects of growth temperature on Er incorporation and segregation behavior were also determined. PL studies, including room‐temperature and thermal quenching experiments, were conducted. © 1996 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Growth and characterization of heteroepitaxial CdTe and ZnTe on Ge(001) buffer layers

David J. Smith, S.‐C. Y. Tsen, Y. P. Chen, S. Sivananthan, and J. B. Posthill

Appl. Phys. Lett. 69, 2086 (1996); http://dx.doi.org/10.1063/1.116888 (3 pages) | Cited 4 times

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The microstructure of heteroepitaxial CdTe (001) and ZnTe(001) epilayers grown on Ge(001) buffer layers by molecular beam epitaxy has been characterized using electron microscopy. Apart from occasional {111} stacking faults originating at the interfacial region, the prevailing defects present in both systems are identified by high‐resolution imaging as perfect Lomer edge dislocations with Burgers vectors of the type a/2〈110〉 parallel to the interface plane, which are indicative of well‐relaxed material. Double‐crystal rocking‐curve measurements using Ge(001) buffer layers give full‐width‐at‐half‐maximum values of 210 arc‐sec for a 7.5μm thick ZnTe film and 125 arc‐sec for a 12μm thick CdTe film. Use of the Ge buffer layers on Si(001) substrates represents a valuable precursor for eventual growth of mercury cadmium telluride since this allows the substrate orientation to be maintained. The buffer layer also permits a substantial reduction of the in situ annealing temperature needed for substrate oxide removal. © 1996 American Institute of Physics.
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68.55.-a Thin film structure and morphology
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Time‐resolved photoluminescence studies of GaN epilayers grown by gas source molecular beam epitaxy on an AlN buffer layer on (111) Si

M. Godlewski, J. P. Bergman, B. Monemar, U. Rossner, and A. Barski

Appl. Phys. Lett. 69, 2089 (1996); http://dx.doi.org/10.1063/1.116889 (3 pages) | Cited 15 times

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Optical properties of GaN epilayers grown by gas source molecular beam epitaxy on a (111) Si substrate with an AlN buffer layer are described. The mechanism of energy transfer between different excitonic emissions is proposed based on the results of time‐resolved photoluminescence (PL) and PL kinetics measurements. It is suggested that tunneling of excitons between bound and free excitons is responsible for the observed PL decay transients and their temperature dependence. © 1996 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics
78.55.Cr III-V semiconductors
71.35.-y Excitons and related phenomena

Epitaxial Pb(Zr0.53Ti0.47)O3/LaNiO3 heterostructures on single crystal substrates

Tao Yu, Yan‐Feng Chen, Zhi‐Guo Liu, Si‐Bei Xiong, Li Sun, Xiao‐Yuan Chen, Lian‐Je Shi, and Nai‐Ben Ming

Appl. Phys. Lett. 69, 2092 (1996); http://dx.doi.org/10.1063/1.116890 (3 pages) | Cited 13 times

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Epitaxial near‐stoichiometric ferroelectric Pb(Zr0.53Ti0.47)O3 thin films were fabricated on epitaxial metallic LaNiO3 electrodes deposited on (001) SrTiO3 and (001) LaAlO3 single crystal substrates by pulsed laser ablation. The P–E hysteresis loop of PZT in the trilayer of Ag/PZT/LNO/STO was measured using the Sawyer–Tower circuit. The remnant polarization Pr and coercive field Ec at room temperature were 30 μC/cm2 and 69.3 kV/cm (peak‐to‐peak voltage=30 V, 50 Hz), respectively. © 1996 American Institute of Physics.
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77.80.Dj Domain structure; hysteresis
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
81.15.Fg Pulsed laser ablation deposition

Transient photocurrent induced in gallium nitride by two‐photon absorption

J. Miragliotta and D. K. Wickenden

Appl. Phys. Lett. 69, 2095 (1996); http://dx.doi.org/10.1063/1.116891 (3 pages) | Cited 10 times

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We have studied the subband gap induced, transient photocurrent in an epitaxial GaN film immersed in an electrolyte solution. For photon energies near the midgap position, one‐ and two‐photon (TP) contributoins were observed in the photocurrent. The one‐photon term exhibited a sublinear intensity dependence and was attributed to carrier generation from traps in the gap. The TP current was negligible for energies below Egap/2. Above this energy, the dispersion was consistent with previous calculations of the TP absorption coefficient [β(ω)] in direct gap semiconductors. A relationship between the TP photocurrent and β(ω) determined a value for the latter of ∼1.5 cm/GW at photon energies above Egap/2. © 1996 American Institute of Physics.
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73.40.Mr Semiconductor-electrolyte contacts
73.50.Pz Photoconduction and photovoltaic effects
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Electroluminescence from erbium and oxygen coimplanted GaN

J. T. Torvik, R. J. Feuerstein, J. I. Pankove, C. H. Qiu, and F. Namavar

Appl. Phys. Lett. 69, 2098 (1996); http://dx.doi.org/10.1063/1.116892 (3 pages) | Cited 33 times

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Room temperature operation of erbium and oxygen coimplanted GaN m‐i‐n (metal–insulator–n‐type) diodes is demonstrated. Erbium related electroluminescence at λ=1.54 μm was detected under reverse bias after a postimplant anneal at 800°C for 45 min in flowing NH3. The integrated light emission intensity showed a linear dependence on applied reverse drive current. © 1996 American Institute of Physics.
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78.60.Fi Electroluminescence
85.60.Jb Light-emitting devices

Suppression of wavy growth in metalorganic vapor phase epitaxy grown GaInAs/InP superlattices

U. Bangert, A. J. Harvey, C. Dieker, and H. Hardtdegen

Appl. Phys. Lett. 69, 2101 (1996); http://dx.doi.org/10.1063/1.116893 (3 pages) | Cited 5 times

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The effects of growth temperature, V–III partial pressure ratio in the gas phase, and the nature of the carrier gas on the morphology of lattice matched InGaAs/InP multiple quantum well stacks are investigated. Preliminary results of an extension of this study to strained InGaAs/InP systems are presented. © 1996 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Radiation hardness of N2O grown oxynitrides assessed using the conductance technique

C. J. Anthony, M. J. Uren, and V. Nayar

Appl. Phys. Lett. 69, 2104 (1996); http://dx.doi.org/10.1063/1.116894 (3 pages)

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Oxynitrides on (100) silicon grown in a N2O ambient have been 60Co gamma irradiated. The conductance technique has been used to show that irradiation under bias can produce lateral charge nonuniformities at the Si:SiO2 interface. The ratio of induced fast to slow interface state density was found to be roughly independent of bias and nitridation, suggesting a common origin for these two types of defects.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
61.80.Ed γ-ray effects
73.20.At Surface states, band structure, electron density of states

Impact of surface stoichiometry control during the initial stages of growth on the stacking fault concentration in ZnSe epilayers grown by molecular beam epitaxy

M. H. Jeon, L. C. Calhoun, B. P. Gila, M. H. Ludwig, and R. M. Park

Appl. Phys. Lett. 69, 2107 (1996); http://dx.doi.org/10.1063/1.116895 (3 pages) | Cited 5 times

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We have determined that the surface stoichiometry maintained during the first five monolayers of ZnSe epitaxial growth can have a significant influence on the stacking fault concentration in 2 μm thick epilayers. In particular, we have been able to minimize the stacking fault concentration to a level in the 104 cm−2 range (comparable to the stacking fault concentration in the ZnSe substrates used for epitaxy) by appropriate selection of a delay time (∼30 s for a substrate temperature of 300 °C) employed during an alternate element (Zn and Se) exposure phase of growth. The delay time in question is the time elapsed between closing the Se shutter and opening the Zn shutter. We show that the surface stoichiometry (Zn to Se atomic ratio) can be tailored during the delay phase since Se thermal desorption occurs at the growth temperature in a controlled fashion from an initially Se‐terminated surface, and, it is postulated that selection of an optimum delay time corresponding to the attainment of a near‐stoichiometric surface results in the growth of low stacking fault concentration material. © 1996 American Institute of Physics.
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61.66.Bi Elemental solids
61.66.Dk Alloys
61.72.Nn Stacking faults and other planar or extended defects
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Identification of compositionally invariant deep levels introduced by plastic strain in epitaxial Ge0.30Si0.70 and deformed bulk Si

P. N. Grillot and S. A. Ringel

Appl. Phys. Lett. 69, 2110 (1996); http://dx.doi.org/10.1063/1.116896 (3 pages) | Cited 4 times

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Deep hole traps introduced by dislocations and other strain relaxation‐induced defects in relaxed, epitaxial Ge0.30Si0.70 layers grown on Si are quantitatively compared to hole traps introduced by plastic deformation of bulk Si. Deep level transient spectroscopy (DLTS) spectra on these samples are shown to be virtually identical in every detail, with the key difference being a translation in temperature that results from the change in valence band energy with GexSi1−x composition. A one‐to‐one correlation is demonstrated for each hole trap detected in p‐type Ge0.30Si0.70 to a given level in p‐type plastically deformed (PD) bulk Si, with the measured differences in DLTS activation energy between each correlated level being approximately equal to the difference in valence band energy (∼0.12 eV) between relaxed Ge0.30Si0.70 and bulk Si. These hole traps are explained to be characteristic of defects induced by plastic strain within the GexSi1−x material system for x=0–0.30, independent of the composition and deformation method, implying invariant defect configurations. This comparison also reveals a hole trap at H(0.60) in Ge0.30Si0.70 not previously reported in PD Si, which we tentatively attribute to hole capture at the dislocation kink sites. © 1996 American Institute of Physics.
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71.55.Cn Elemental semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
81.40.Lm Deformation, plasticity, and creep

The dose, energy, and time dependence of silicon self‐implantation induced transient enhanced diffusion at 750 °C

H. S. Chao, P. B. Griffin, J. D. Plummer, and C. S. Rafferty

Appl. Phys. Lett. 69, 2113 (1996); http://dx.doi.org/10.1063/1.116897 (3 pages) | Cited 19 times

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The short anneal time behavior of transient enhanced diffusion of dopants in silicon is investigated experimentally using a buried boron marker layer structure and varying Si implant doses and implant energies. The diffusion behavior of the marker layer shows that the diffusivity enhancements are, to the first order, independent of the implant conditions at short anneal times, while the overall transient motion increases with increasing implant conditions. The data are analyzed using an interstitial clustering model that includes both cluster evaporation and cluster growth terms. © 1996 American Institute of Physics.
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61.72.uf Ge and Si
66.30.J- Diffusion of impurities

Metalorganic chemical vapor deposition of monocrystalline GaN thin films on β‐LiGaO2 substrates

P. Kung, A. Saxler, X. Zhang, D. Walker, R. Lavado, and M. Razeghi

Appl. Phys. Lett. 69, 2116 (1996); http://dx.doi.org/10.1063/1.116898 (3 pages) | Cited 34 times

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We report the metalorganic chemical vapor deposition growth and characterization of monocrystalline GaN thin films on β‐LiGaO2 substrates. The influence of the growth temperature on the crystal quality was studied. The structural, electrical, and optical properties of the films were assessed through scanning electron microscopy, x‐ray diffraction, Hall measurements, optical transmission, photoluminescence. © 1996 American Institute of Physics.
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73.61.Ey III-V semiconductors
68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.66.Fd III-V semiconductors

Planar microwave devices fabricated by ion‐implantation patterning of high‐temperature superconductors

D. C. DeGroot, D. A. Rudman, Kuan Zhang, Q. Y. Ma, H. Kato, and N. A. F. Jaeger

Appl. Phys. Lett. 69, 2119 (1996); http://dx.doi.org/10.1063/1.116899 (3 pages) | Cited 7 times

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We have applied ion‐implantation inhibit patterning as a new method of fabricating low‐loss microwave transmission lines in high‐temperature superconductor thin films. To determine the effectiveness of this technique, we fabricated coplanar waveguide transmission lines in YBa2Cu3O7−δ thin films that had been deposited on LaAlO3 substrates using pulsed laser deposition. Microwave characterizations of these lines are compared to a reference line fabricated with conventional ion milling. At 76 K and 12 GHz, the attenuation constants of the ion‐implanted transmission lines are approximated 0.02 dB/mm, and the overall loss response is indistinguishable from that of the ion‐milled device. © 1996 American Institute of Physics.
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85.25.Hv Superconducting logic elements and memory devices; microelectronic circuits
84.40.Lj Microwave integrated electronics
74.78.-w Superconducting films and low-dimensional structures

Terahertz radiation from superconducting YBa2Cu3O7−δ thin films excited by femtosecond optical pulses

M. Hangyo, S. Tomozawa, Y. Murakami, M. Tonouchi, M. Tani, Z. Wang, K. Sakai, and S. Nakashima

Appl. Phys. Lett. 69, 2122 (1996); http://dx.doi.org/10.1063/1.117175 (3 pages) | Cited 44 times

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Ultrashort electromagnetic waves (600 fs width) from superconducting YBCO thin films have been observed by irradiating current‐biased samples with femtosecond optical laser pulses (80 fs width). The Fourier component of the pulse extends up to ∼2 THz. The characteristics of the radiation are studied and the radiation mechanism is ascribed to the ultrafast supercurrent modulation by the laser pulses, which induce the nonequilibrium superconductivity. © 1996 American Institute of Physics.
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74.25.N- Response to electromagnetic fields
74.78.-w Superconducting films and low-dimensional structures

Low noise high‐temperature superconducting bolometers for infrared imaging

S. J. Berkowitz, A. S. Hirahara, K. Char, and E. N. Grossman

Appl. Phys. Lett. 69, 2125 (1996); http://dx.doi.org/10.1063/1.117174 (3 pages) | Cited 15 times

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High‐temperature superconducting bolometric infrared detectors offer the promise of matching the sensitivity of HgCdTe detectors, but with an extended detection range to longer wavelengths (λ≳15μm). We fabricated high‐temperature superconducting bolometers using an all‐epitaxial micromachining technology based upon a YBa2Cu3Ox thin film on a yttria‐stabilized zirconia free‐standing 50×50μm2 membrane supported on a LaAlO3 substrate. This structure has simultaneously a low thermal conductance and a low heat capacity. Using this technology, we have made array‐compatible pixels for infrared camera applications with optical noise equivalent powers as low as 6.3×10−13 W/√Hz at 32 Hz. Over more than 1 octave of frequency range, these bolometers are limited by fundamental (chiefly phonon) noise sources rather than excess film noise. © 1996 American Institute of Physics.
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85.25.Pb Superconducting infrared, submillimeter and millimeter wave detectors
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
74.25.Gz Optical properties
74.78.-w Superconducting films and low-dimensional structures

Partitioning of Si in a Fe87Zr7Si4B2 nanocrystalline soft magnetic alloy

Y. Zhang, K. Hono, A. Inoue, and T. Sakurai

Appl. Phys. Lett. 69, 2128 (1996); http://dx.doi.org/10.1063/1.117176 (3 pages) | Cited 7 times

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We have studied partitioning of Si in nanocrystalline Fe–Zr–Si–B soft magnetic alloy by atom probe field ion microscopy (APFIM). Unlike our expectation from our previous results in nanocrystalline Fe–Si–B–Nb–Cu alloy, we have found that Si atoms are rejected from α‐Fe primary crystals and partitioned into the residual amorphous phase. This result suggests that Si addition does not cause reduction in inherent magnetostriction of α‐Fe nanoparticles, but it brings the volume fraction of the α‐Fe particles to an optimum value so that the average magnetostriction becomes zero. This conclusion has been strengthened by comparing the changes in magnetostriction constants as a function of Si content in Fe–Zr–Si–B and Fe–Si–B–Nb–Cu alloys. © 1996 American Institute of Physics.
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75.50.Kj Amorphous and quasicrystalline magnetic materials
75.50.Bb Fe and its alloys
68.37.Vj Field emission and field-ion microscopy

Electron paramagnetic resonance characterization of nonuniform distribution of hydrogen in silica optical fibers

J. Li, R. L. Lehman, and G. H. Sigel

Appl. Phys. Lett. 69, 2131 (1996); http://dx.doi.org/10.1063/1.117177 (3 pages)

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The hydrogen distribution within low‐OH silica optical fibers has been characterized by electron paramagnetic resonance in combination with a chemical etch‐back technique. The 74 G doublet, the signal generated by a hydrogen hyperfine structure of the Si E′ center, was used to investigate the spatial distribution of hydrogen reaction products in silica optical fiber and, in particular, the reaction between the twofold coordinated silicon and hydrogen. A nonuniform distribution of the 74 G species was observed with the highest concentration near the fiber surface, indicative of a corresponding nonuniform distribution of hydrogen. The polymer fiber coating appears to be the primary source of the trace amounts of hydrogen observed in the silica fibers. © 1996 American Institute of Physics.
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42.81.Cn Fiber testing and measurement of fiber parameters
76.30.-v Electron paramagnetic resonance and relaxation
61.72.S- Impurities in crystals

Reduction in flux divergence at vias for improved electromigration in multilayered AlCu interconnects

Larry Ting, Qi‐Zhong Hong, and Wei‐Yung Hsu

Appl. Phys. Lett. 69, 2134 (1996); http://dx.doi.org/10.1063/1.117178 (3 pages) | Cited 1 time

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Using of W‐plug vias in AlCu interconnects is known to significantly degrade electromigration (EM) performance because W is a diffusion barrier and prevents the depleting species by EM from being replenished at the via. In the present study, we demonstrate that this problem of limited source for EM migrating species can be dramatically alleviated in a multilayered metallization of TiN/AlCu/TiN using Al‐plug vias. EM lifetime improvements as large as by an order of magnitude are accomplished by reducing the flux divergence at the Al‐plug via. This flux divergence is critically determined by the effective thickness of some transition metal films at the via, which include a Ti/TiN stack for the via barrier and a TiN layer of antireflection coating for the bottom level metal lead. Scanning electron microscopy failure analysis also verifies that the samples with W‐plug vias have the void damages consistently located at the via. For the samples with Al‐plug vias and with the flux divergence at the via being largely reduced, the void failures locate on the metal lead and no visible damage at or within the via, indicating the reduced flux divergence at the via has become smaller than those generated on the metal lead due to microstructural variations. © 1996 American Institute of Physics.
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66.30.Qa Electromigration
85.40.Ls Metallization, contacts, interconnects; device isolation
FREE

Erratum: ‘‘Parameterization of the optical functions of amorphous materials in the interband region’’ [Appl. Phys. Lett. 69, 371 (1996)]

G. E. Jellison and F. A. Modine

Appl. Phys. Lett. 69, 2137 (1996); http://dx.doi.org/10.1063/1.118155 (1 page) | Cited 167 times

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78.20.Bh Theory, models, and numerical simulation
78.40.Pg Disordered solids
99.10.Cd Errata
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