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27 May 1996

Volume 68, Issue 22, pp. 3063-3198

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Extraction of real‐space correlation function of a rough surface by light scattering using diode array detectors

Y. P. Zhao, H.‐N. Yang, G.‐C. Wang, and T.‐M. Lu

Appl. Phys. Lett. 68, 3063 (1996); http://dx.doi.org/10.1063/1.116423 (3 pages) | Cited 10 times

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Based on an inverse transform method originally developed by Chandley and modified by us in the present work, we show that the height‐height correlation function of a rough Si surface can be obtained directly from a single intensity distribution profile of light scattering. A novel diode array detectors arrangement was used to obtain the intensity profile. The roughness parameters, including the interface width, lateral correlation length, and roughness exponent were extracted from the height‐height correlation function and were compared with that obtained by an atomic force microscope. © 1996 American Institute of Physics.
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61.05.C- X-ray diffraction and scattering
68.35.B- Structure of clean surfaces (and surface reconstruction)

Spurious momentum mismatch introduced by an approximate model of acousto‐optic interactions

Yih‐Tyng Wu and Betty Lise Anderson

Appl. Phys. Lett. 68, 3066 (1996); http://dx.doi.org/10.1063/1.116424 (3 pages)

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In acousto‐optic interactions, the concept of momentum mismatch introduced by some books is misleading and nonexistent because the mismatch itself is caused by the approximate model used to explain the interactions. The so‐called mismatch is very small and should not be handled with an approximate model. We use an exact model to satisfy Bragg condition, conservation of energy, and conservation of momentum. The difference between the exact model and the approximate model is actually what causes the mismatch. © 1996 American Institute of Physics.
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43.35.Sx Acoustooptical effects, optoacoustics, acoustical visualization, acoustical microscopy, and acoustical holography

Compaction‐ and photoelastic‐induced index changes in fiber Bragg gratings

H. G. Limberger, P.‐Y. Fonjallaz, R. P. Salathé, and F. Cochet

Appl. Phys. Lett. 68, 3069 (1996); http://dx.doi.org/10.1063/1.116425 (3 pages) | Cited 49 times

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The tension on the core of single‐mode fibers is strongly increased by the formation of a Bragg grating. This tension increase lowers the refractive index because of the photoelastic effect. On the other hand, the compaction of the core network results in an increased refractive index. The two contributions are evaluated from axial stress measurements, from the determined index modulation amplitude, and from the mean index change of the Bragg gratings. The total Bragg grating index modulation is smaller than the compaction‐induced index modulation by 30%–35% because of the photoelastic effect. © 1996 American Institute of Physics.
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42.81.-i Fiber optics

Faraday rotation of Hoya FR5 glass at cryogenic temperature

Hyeon Gon Lee, Y. H. Won, and G. S. Lee

Appl. Phys. Lett. 68, 3072 (1996); http://dx.doi.org/10.1063/1.116426 (3 pages) | Cited 3 times

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Faraday rotation and magnetization in Hoya FR5 glass is investigated in a magnetic field up to 80 kG under cryogenic temperature between 4.2 K and 10 K at the wavelength of 514.5 nm. For H/T≳10 kG K−1, the saturation is observed both in magnetization and in Faraday rotation and is interpreted by using the quantum theory of paramagnetism about the doped Tb3+ active ion. It is found that the temperature dependence of the Verdet constant is correlated with the magnetic susceptibility and the dispersion of the Verdet constant is due to the effective electric dipole transition of 4f8→4f75d1 with the resonance wavelength of 213 nm. © 1996 American Institute of Physics.
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42.70.Ce Glasses, quartz
78.20.Ls Magneto-optical effects

Double acceptor doped Ge: A new medium for inter‐valence‐band lasers

E. Bründermann, A. M. Linhart, L. Reichertz, H. P. Röser, O. D. Dubon, W. L. Hansen, G. Sirmain, and E. E. Haller

Appl. Phys. Lett. 68, 3075 (1996); http://dx.doi.org/10.1063/1.116427 (3 pages) | Cited 19 times

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We report on intervalence‐band laser emission from Be‐ and Zn‐doped germanium crystals. The duty cycle of 10−3 at a repetition rate of 1 kHz is one order of magnitude larger than the highest duty cycle reported for p‐Ge lasers doped by group II acceptors. This improvement is due to the much larger hole binding energy of double acceptors Be and Zn which results in a strong reduction of the internal absorption of the generated far‐infrared radiation. Laser action has been achieved with crystal volumes as small as 0.04 cm−3, and a laser pulse length of 25 μs has been reached. Germanium crystals doped with these acceptors may offer an opportunity for achieving the ultimate goal of continuous wave operation. © 1996 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
78.45.+h Stimulated emission
44.30.+v Heat flow in porous media
72.20.My Galvanomagnetic and other magnetotransport effects

Localized Kerr‐type nonlinearities in GaAs/AlGaAs multiple quantum well structures at 1.55 μm

C. J. Hamilton, J. H. Marsh, D. C. Hutchings, J. S. Aitchison, G. T. Kennedy, and W. Sibbett

Appl. Phys. Lett. 68, 3078 (1996); http://dx.doi.org/10.1063/1.116428 (3 pages) | Cited 13 times

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We report the use of a novel impurity free vacancy disordering technique which has been used to produce waveguides with different Kerr‐type nonlinear coefficients. The technique relies on standard SiO2 dielectric caps to promote disordering and Ga2O3 caps to suppress disordering. Band‐gap shifts of around 40 nm and consequent changes in n2 of more than 60% are reported. © 1996 American Institute of Physics.
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66.30.J- Diffusion of impurities
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials

Optical switching of coherent VO2 precipitates formed in sapphire by ion implantation and annealing

Laurence A. Gea and L. A. Boatner

Appl. Phys. Lett. 68, 3081 (1996); http://dx.doi.org/10.1063/1.116429 (3 pages) | Cited 22 times

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Coherent precipitates of vanadium dioxide have been formed in the near‐surface region of sapphire by the stoichiometric coimplantation of vanadium and oxygen combined with subsequent thermal processing at temperatures ranging from 700 to 1000 °C. The embedded VO2 precipitates, which are three‐dimensionally oriented with respect to the Al2O3 host lattice, undergo a first‐order monoclinic‐to‐tetragonal (and also semiconducting‐to‐metallic) phase transition at ∼77 °C. This transformation is accompanied by a significant variation in the optical transmission of the implanted region and results in the formation of an optically active, thermally ‘‘switchable’’ surface region on Al2O3. © 1996 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
78.66.Li Other semiconductors
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Ion implantation‐induced strong photosensitivity in high‐purity fused silica: Correlation of index changes with VUV color centers

M. Verhaegen, J. L. Brebner, L. B. Allard, and J. Albert

Appl. Phys. Lett. 68, 3084 (1996); http://dx.doi.org/10.1063/1.116430 (3 pages) | Cited 8 times

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We have studied optical changes induced by ArF (6.4 eV/193 nm) excimer laser light illumination of high purity SiO2 implanted with Si 2+ (5 MeV) at a fluence of 1015 ions/cm2. Optical absorption was measured from 3 eV (400 nm) to 8 eV (155 nm) and showed evidence of several well‐defined absorption bands. A correlation in the bleaching behavior appears to exist between the so‐called D band (located at 7.15 eV) and the well‐known B2α band which is attributed to oxygen vacancies. Changes in the refractive index as a function of ArF illumination were measured and found to be in good quantitative agreement with a Kramers–Kronig analysis of the optical absorption data. © 1996 American Institute of Physics.
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78.66.Jg Amorphous semiconductors; glasses
42.70.Ce Glasses, quartz
78.66.Nk Insulators

Metallic particle sizing on flat surfaces: Application to conducting substrates

F. Moreno, J. M. Saiz, P. J. Valle, and F. González

Appl. Phys. Lett. 68, 3087 (1996); http://dx.doi.org/10.1063/1.116431 (3 pages) | Cited 12 times

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A fast and accurate microsizing method is introduced and analyzed for metallic protuberances on flat substrates. It is based on the measurement of the minima angular positions of the S‐polarized far field scattering patterns at normal incidence. The proposed method has been theoretically and experimentally checked for both cylindrical and spherical metallic protuberances on conducting flat substrates. The excellent agreement between theory and experiment proves the efficiency of the method. We also comment on the application of this method for other protuberance geometries and different substrates other than metallic. © 1996 American Institute of Physics.
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42.25.Fx Diffraction and scattering
68.35.B- Structure of clean surfaces (and surface reconstruction)

Evolution of the crystallographic position of As impurities in heavily doped Si crystals as their electrical activity changes

A. Herrera‐Gómez, P. M. Rousseau, G. Materlik, T. Kendelewicz, J. C. Woicik, P. B. Griffin, J. Plummer, and W. E. Spicer

Appl. Phys. Lett. 68, 3090 (1996); http://dx.doi.org/10.1063/1.116432 (3 pages) | Cited 18 times

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Arsenic impurities in silicon can be electrically activated beyond their electrical solubility to as high as 4×1021/cm3 by ion implantation and laser melting; further annealing decreases this activity to its equilibrium saturation level. To characterize the deactivation process, we used x‐ray standing‐wave spectroscopy. Hall effect, and secondary‐ion‐mass spectroscopy. Our results indicate that the As impurities remain in substitutional positions even after 85% of the activation has been lost, so deactivation cannot be due to As migration to interstitial sites or to large precipitates. © 1996 American Institute of Physics.
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61.72.uf Ge and Si

Link‐up of 90° domain boundaries with interface dislocations in BaTiO3/LaAlO3

Z. R. Dai, Z. L. Wang, X. F. Duan, and Jiming Zhang

Appl. Phys. Lett. 68, 3093 (1996); http://dx.doi.org/10.1063/1.116433 (3 pages) | Cited 17 times

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Interface microstructures of BaTiO3/LaAlO3 grown by metalorganic chemical vapor deposition (MOCVD) are studied using high‐resolution transmission electron microscopy (HRTEM). Interface dislocations in BaTiO3/LaAlO3 have been shown to be directly linked up with the 90° domain boundaries in BaTiO3. This association is a result of strain relief due to a phase transformation when cooled down from the growth temperature. The Burgers vector of the interface dislocations is 〈010〉. © 1996 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
77.80.-e Ferroelectricity and antiferroelectricity

Amorphous films formed by solid‐state reaction in an immiscible Y–Mo system and their structural relaxation

Y. G. Chen and B. X. Liu

Appl. Phys. Lett. 68, 3096 (1996); http://dx.doi.org/10.1063/1.116434 (3 pages) | Cited 21 times

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Amorphous films of 300 nm thick were obtained by solid state reaction in an immiscible Y–Mo system with a positive heat of mixing being +26 kJ/mol. The experimental results revealed that the Y51Mo49 multilayers, including 19% interfacial atoms, were vitrified by thermal annealing at 300 °C for one and half hours, and that the formed amorphous films recrystallized at about 600 °C. These confirmed that the excess interfacial free energy stored in the multilayered films elevated the initial energetic state of the multilayers to a level higher than that of the amorphous phase, providing a major driving force in solid state amorphization. The elastic modulus and hardness changes of the formed amorphous films upon annealing were characterized by nanoindentation, and the results were in accordance with the proposed free volume model for the amorphous structure. ] © 1996 American Institute of Physics.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics

Bias current dependent resistance peaks in NiFe/Ag giant magnetoresistance multilayers

L. S. Kirschenbaum, C. T. Rogers, P. D. Beale, S. E. Russek, and S. C. Sanders

Appl. Phys. Lett. 68, 3099 (1996); http://dx.doi.org/10.1063/1.116435 (3 pages) | Cited 1 time

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We show that thin‐film Ni82Fe18/Ag multilayer structures display multiple peaks in their magnetoresistance curves when biased at current densities above 106 A/cm2. These peaks appear for annealed and unannealed structures, and their number is correlated with the number of NiFe layers. At high bias currents, the peak positions shift linearly with the internal magnetic field created by the bias current. The peak positions extrapolate to nonzero fields at zero bias currents, providing an upper bound on the magnetic layer‐layer coupling strength of J0≊10−20 J (kB×700 K). The peak positions do not shift with temperature over the range 200–375 K; their widths narrow with increasing temperature. The single‐domain magnetic moment μ is estimated as 10−17 J/T (106 μB) from the peak widths of ∼0.8 kA/m. © 1996 American Institute of Physics.
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75.47.De Giant magnetoresistance
73.61.At Metal and metallic alloys
75.50.Bb Fe and its alloys
75.60.-d Domain effects, magnetization curves, and hysteresis

Chemical beam epitaxial growth of Si‐doped GaAs and InP by using silicon tetraiodide

Shigekazu Izumi, Norio Hayafuji, Kazuhiko Ito, Kazuhiko Sato, and Mutsuyuki Otsubo

Appl. Phys. Lett. 68, 3102 (1996); http://dx.doi.org/10.1063/1.116436 (3 pages) | Cited 4 times

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Silicon tetraiodide (SiI4), which has a very weak Si–I bond strength (70 kcal/mol), is successfully employed as a novel Si dopant in the chemical beam epitaxy of GaAs and InP. No precracking is necessary before supplying SiI4 with He carrier gas. High electrical quality is ascertained for both GaAs and InP with linear Si doping controllability in the range from 2×1016 to 6×1018 cm−3 with a uniformity of less than 2% within a 3‐in.‐diam area. The electron mobility in a GaAs with a carrier concentration of 1×1017 cm−3 is 4400 cm2/V s and that in InP with a carrier concentration of 4×1017 cm−3 is 2400 cm2/V s, respectively. Abrupt interfaces and precise on‐off controllability without any memory effect is also confirmed by secondary‐ion‐mass, spectroscopy measurements. The electrical activation ratio of Si in SiI4 for both GaAs and InP is almost 100% in the range studied here. These versatile features suggest that SiI4 is a promising candidate as a Si dopant source for chemical beam epitaxy growth. © 1996 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Band‐edge photoluminescence from pseudomorphic Si0.96Sn0.04 alloy

Al‐Sameen T. Khan, Paul R. Berger, Fernando J. Guarin, and Subramanian S. Iyer

Appl. Phys. Lett. 68, 3105 (1996); http://dx.doi.org/10.1063/1.116437 (3 pages) | Cited 7 times

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Band‐edge related photoluminescence from a strained Si0.96Sn0.04 alloy grown by molecular beam epitaxy on Si(100) substrate has been seen for the first time. We report band‐edge related photoluminescence from a compressively strained pseudomorphic Si0.96Sn0.04 alloy. The luminescence observed consisted of two dominant features, a well‐resolved band‐edge luminescence consisting of a no‐phonon and a transverse optical phonon replica, and a deep‐level broad luminescence peak around 770 meV. The band‐edge feature is attributed to a no‐phonon free excitonic recombination in the binary alloy and exhibits a near linear power dependence. We also observe a red shift of the energy gap of Si0.96Sn0.04 alloy with respect to Si, which corresponds to the bulk alloy effect. © 1996 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
78.66.Li Other semiconductors

Structural nature of the Si/SiO2 interface through infrared spectroscopy

R. A. B. Devine

Appl. Phys. Lett. 68, 3108 (1996); http://dx.doi.org/10.1063/1.116438 (3 pages) | Cited 42 times

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The spatial variations of the transverse‐optic and longitudinal‐optic mode vibrations of the bridging oxygen asymmetric stretch have been studied in the region of the SiO2/Si interface in thermally grown oxides. Comparing the behavior of the two modes it is concluded that vibrational frequency shifts are due primarily to stoichiometry changes and not stress or densification. Fitting to and deconvolution of the measured peak lineshifts as a function of oxide thickness enables us to deduce that the region of stoichiometry variation is ≤1.6 nm. © 1996 American Institute of Physics.
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68.55.-a Thin film structure and morphology
78.30.-j Infrared and Raman spectra

Using doping superlattices to study transient‐enhanced diffusion of boron in regrown silicon

K. S. Jones, R. G. Elliman, M. M. Petravić, and P. Kringhøj

Appl. Phys. Lett. 68, 3111 (1996); http://dx.doi.org/10.1063/1.116439 (3 pages) | Cited 24 times

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A boron‐doped silicon superlattice consisting of three boron spikes separated by 1700 Å of undoped silicon has been grown by molecular beam epitaxy and used to study the evolution of point defects following an amorphizing implant of Si+. After MBE growth, the wafer was implanted at 77 K with either 146 or 292 keV Si+ at a dose of 5×1015/cm2. These implants produced amorphous layer depths that coincided with the depths of either the middle B peak or just below the deepest B peak. The samples were then annealed at 800 °C in an Ar ambient. Secondary‐ion‐mass spectrometry and transmission electron microscopy were used to monitor the diffusion of the boron spikes upon annealing and the evolution of the extended defects upon annealing, respectively. For the lower‐energy sample, an enhancement in the B diffusivity of over 500× was observed for both the surface B spike and the deepest B spike. The higher‐energy implant shows conclusively that the back flow of interstitials into the regrown region is coming from the end‐of‐range damage just below the amorphous/crystalline interface. These results show that for these implant conditions the end‐of‐range damage does not act as a barrier to flow of interstitials to the surface. In addition it is noted that boron in the regrown silicon does not cluster whereas the boron below the amorphous crystalline interface does. Both of these features must be accounted for when modeling boron diffusion in regrown silicon. © 1996 American Institute of Physics.
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66.30.J- Diffusion of impurities
61.72.uf Ge and Si

Potential chirp‐free characteristics (negative chirp parameter) in electroabsorption modulation using a wide tensile‐strained quantum well structure

Takayuki Yamanaka, Koichi Wakita, and Kiyoyuki Yokoyama

Appl. Phys. Lett. 68, 3114 (1996); http://dx.doi.org/10.1063/1.115795 (3 pages) | Cited 17 times

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The possibility of nearly chirp‐free electroabsorption (EA) characteristics in intensity modulation at an operating wavelength of 1.55 μm is studied theoretically. The TE‐polarized EA spectra, their Kramers–Krönig (K–K) transformed refractive index changes, and the chirp parameters derived under both small‐signal and large‐signal conditions are calculated including excitonic effect within the framework of the effective mass theory. We investigate on the basis of the simulated EA results how to keep chirp parameters always negative. This can be accomplished by following two successive steps: (1) Widen the well width to increase the Stark shift. This makes it easier for the chirp parameter to turn negative at smaller applied electric field. (2) Apply tensile strain to the wide QW to induce a negative refractive index changes even in the vicinity of zero electric fields, indicating that there exists a desirable condition where the chirp parameter is negative independently of applied fields. © 1996 American Institute of Physics.
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78.66.-w Optical properties of specific thin films

Electric field screening in a multiple‐quantum‐well optically addressed spatial light modulator

S. L. Smith, L. Hesselink, and A. Partovi

Appl. Phys. Lett. 68, 3117 (1996); http://dx.doi.org/10.1063/1.115796 (3 pages) | Cited 5 times

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The transmission and photocurrent of a multiple‐quantum‐well optically addressed spatial light modulator are measured to study the screening dynamics of the internal electric field under uniform illumination. The response is modeled with a numerical device simulator which solves the conventional drift‐diffusion transport equations. Evidence is found for bipolar transport, and the photocurrent response at low internal fields is shown to decay due to the transit time of carriers across the quantum well region. For large internal fields the photocurrent response saturates and the corresponding screening rate is estimated using an analytical device model. © 1996 American Institute of Physics.
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85.30.De Semiconductor-device characterization, design, and modeling
73.50.Pz Photoconduction and photovoltaic effects
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Exciton diffusion and dissociation in a poly(p‐phenylenevinylene)/C60 heterojunction photovoltaic cell

J. J. M. Halls, K. Pichler, R. H. Friend, S. C. Moratti, and A. B. Holmes

Appl. Phys. Lett. 68, 3120 (1996); http://dx.doi.org/10.1063/1.115797 (3 pages) | Cited 317 times

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We report measurements of the photovoltaic response of two‐layer photocells formed with layers of the conjugated polymer poly(phenylenevinylene), PPV and fullerene, C60, formed between indium‐tin oxide and aluminum electrodes. Peak quantum efficiencies of up to ∼9% (electrons collected per incident photon) were measured under short‐circuit conditions. We model the photovoltaic response as arising from excitons photogenerated in the PPV layer which are able to diffuse to the interface with the C60 layer where they are ionized. We obtain a value for the exciton diffusion range of 7±1 nm, both from the spectral response and from the absolute efficiency. We demonstrate that the branching ratio for the creation of singlet excitons from absorbed photons is close to unity. © 1996 American Institute of Physics.
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73.50.Pz Photoconduction and photovoltaic effects
78.66.-w Optical properties of specific thin films

InAs quantum boxes: Highly efficient radiative traps for light emitting devices on Si

J. M. Gérard, O. Cabrol, and B. Sermage

Appl. Phys. Lett. 68, 3123 (1996); http://dx.doi.org/10.1063/1.115798 (3 pages) | Cited 63 times

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We have compared by photoluminescence (PL) the radiative quantum efficiencies η of an array of InAs/GaAs quantum boxes (QBs) obtained by self‐organized growth and of a single high quality InGaAs quantum well (QW). On GaAs substrates, η is essentially the same for both structures. A growth on a commercial GaAs‐on‐Si substrate entails drastic quenching of the integrated PL intensity and shortening of the carrier lifetime τ for the InGaAs QW, whereas both τ and η are not modified for the QB array. The efficient carrier capture by InAs QBs, combined with the localized nature of QB excitons hinders in this case the carrier diffusion toward dislocations. These superior properties of QBs on Si, which are observed over a wide range of excitation powers and for temperatures up to 300 K, opens a novel route toward efficient and reliable light emitters on Si. © 1996 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.55.Cr III-V semiconductors

Effects of hydrogen on structural relaxation and defect evolution in amorphous silicon

Y. Hiroyama, T. Motooka, R. Suzuki, Y. Hirano, and F. Sato

Appl. Phys. Lett. 68, 3126 (1996); http://dx.doi.org/10.1063/1.115799 (3 pages) | Cited 4 times

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Hydrogenation effects on the structural relaxation and defect evolution in amorphous silicon (a‐Si) prepared by ion implantation and evaporation have been investigated using Raman scattering spectroscopy and positron lifetime measurements. Bond angle deviation Δθ in nonhydrogenated a‐Si was significantly reduced due to 300 °C annealing in atomic hydrogen atmosphere. This indicates that the reduction in Δθ of hydrogenated amorphous silicon (a‐Si:H) is not only due to relaxation during the deposition process of a‐Si:H films as proposed by Jackson et al. [Philos. Mag. B 64, 611 (1991)] but also due to posthydrogenation of nonhydrogenated a‐Si. It was also found that agglomeration of vacancy‐type defects in evaporated a‐Si during 450 °C annealing is enhanced after posthydrogenation, while no remarkable enhancement can be seen in a‐Si prepared by ion implantation. © 1996 American Institute of Physics.
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61.43.Dq Amorphous semiconductors, metals, and alloys
61.72.J- Point defects and defect clusters
71.55.Jv Disordered structures; amorphous and glassy solids

Wet thermal oxidation of AlAsSb lattice matched to InP for optoelectronic applications

O. Blum, K. M. Geib, M. J. Hafich, J. F. Klem, and C. I. H. Ashby

Appl. Phys. Lett. 68, 3129 (1996); http://dx.doi.org/10.1063/1.115800 (3 pages) | Cited 22 times

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We demonstrate wet thermal oxidation of an AlAsSb layer lattice matched to an InP substrate. Oxidation in an InGaAs/AlAsSb/InGaAs structure proceeds in a lateral direction, producing an oxide layer embedded between two layers of InGaAs. Auger analysis and Raman spectroscopy indicate conversion of the AlAsSb into an aluminum oxide with an elemental antimony layer at the top oxide‐InGaAs interface. Scanning electron microscope cross‐sectional views of partially and fully oxidized samples are also presented.
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81.65.Mq Oxidation
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
78.30.Fs III-V and II-VI semiconductors

Transport characterization of in‐plane gate devices fabricated by direct epitaxial growth on patterned substrates

M. Dilger, R. J. Haug, K. Eberl, A. Kurtenbach, Y. Kershaw, and K. v. Klitzing

Appl. Phys. Lett. 68, 3132 (1996); http://dx.doi.org/10.1063/1.115801 (3 pages) | Cited 6 times

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Direct molecular‐beam epitaxial growth of GaAs/AlxGa1−xAs heterostructures on bow‐tie shaped constrictions, prepatterned on GaAs substrates is used to fabricate in‐plane gate transistors. The fabricated devices can be tuned by applying voltages to in‐plane gates, which are also realized during the epitaxial growth. In this way, complete in‐plane gate transistors are fabricated in a single growth process. Transport measurements of the devices at 1.3 K show conductance quantization or Coulomb blockade depending on the width of the constriction. The Coulomb blockade effect in the narrowest structures is caused by the formation of a self‐assembled quantum dot in the center of the constriction. © 1996 American Institute of Physics.
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85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.23.Hk Coulomb blockade; single-electron tunneling

Change in bulk defect density of hydrogenated amorphous silicon by bias stress in thin film transistor structures

Hyuk‐Ryeol Park, Dong‐Sun Oh, and Jin Jang

Appl. Phys. Lett. 68, 3135 (1996); http://dx.doi.org/10.1063/1.115802 (3 pages) | Cited 2 times

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The changes in defect density of hydrogenated amorphous silicon (a‐Si:H) in thin film transistor (TFT) structures by prolonged bias stress or light soaking have been studied through constant photocurrent method (CPM) measurements. The CPM absorptions due to defect absorptions do not change after positive or negative bias‐stress. On the other hand, the CPM absorptions due to dangling bond defects increase remarkably after light soaking. These experimental results demonstrate that the bulk defect density of a‐Si:H in TFT structure is not changed after long time bias stress even though the characteristics of the TFT degrade significantly. © 1996 American Institute of Physics.
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72.80.Ng Disordered solids
73.61.Jc Amorphous semiconductors; glasses
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