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1 Jan 2000

Volume 87, Issue 1, pp. 1-623

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Abnormal temperature dependence of band-gap energies observed in (InAs)/(GaAs) and (InP)/(GaP) superlattices with strong lateral composition modulation

Shu-Tsun Chou

J. Appl. Phys. 87, 285 (2000); http://dx.doi.org/10.1063/1.371857 (4 pages) | Cited 2 times

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An abnormal variation of the band-gap energy with temperature was observed in both the (InAs)2.2/(GaAs)2 and (InP)2/(GaP)2 short-period-superlattice (SPS) structures. Strong lateral composition modulation induced two horizontally adjacent regions with different In content in the SPS regions. Due to the difference of thermal expansion coefficients among the substrate and the two adjacent regions in the SPS structures, it is proposed that a thermal strain has been generated and accommodated by altering the lattice constant in the growth direction. The magnitude of lattice variation depends on the relative thermal expansion and compressibility of the two adjacent materials. The net modification of the lattice thermal expansion in the In-rich region results in the abnormal variation of band-gap energies with temperature. © 2000 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
65.40.De Thermal expansion; thermomechanical effects
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Valence band photoemission, band bending, and ionization energy of GaAs(100) treated in alcoholic sulfide solution

Mikhail V. Lebedev and Masakazu Aono

J. Appl. Phys. 87, 289 (2000); http://dx.doi.org/10.1063/1.371858 (6 pages) | Cited 6 times

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Valence band and Fermi level position on a p-GaAs(100) surface treated in the solution of ammonium sulfide in isopropanol have been studied by ultraviolet photoemission spectroscopy. Sulfur treatment and subsequent annealing affect features of 0.8 and 3.7 eV binding energy in normal emission valence band spectrum of a bare semiconductor and the effect is related to the variation of surface chemical bonds. It has been found that after sulfur treatment surface band bending and ionization energy increase by 0.4 and 0.3 eV, respectively. Annealing at 310 °C or higher results in the decrease of the ionization energy with the temperature. The position of the surface Fermi level sharply changes from 1.5–1.20 to 0.85 eV above the valence band maximum when the surface is annealed at 360 °C. © 2000 American Institute of Physics.
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79.60.Dp Adsorbed layers and thin films
81.65.Rv Passivation
73.20.Hb Impurity and defect levels; energy states of adsorbed species

Dependence of indium–tin–oxide work function on surface cleaning method as studied by ultraviolet and x-ray photoemission spectroscopies

Kiyoshi Sugiyama, Hisao Ishii, Yukio Ouchi, and Kazuhiko Seki

J. Appl. Phys. 87, 295 (2000); http://dx.doi.org/10.1063/1.371859 (4 pages) | Cited 158 times

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The effect of the method used to clean indium–tin–oxide (ITO) on its work function was investigated by ultraviolet photoemission spectroscopy (UPS) and x-ray photoemission spectroscopy. With only ultrasonic cleaning in the organic solvent, considerable carbon contamination remained on the ITO surface and the work function was low (4.5 eV). In contrast, ultraviolet (UV)–ozone treatment removed significant carbon contamination, with an increase in the work function to 4.75 eV, which improves the hole-injection efficiency into the organic hole-transport layer in organic electroluminescent devices. Although carbon contamination on the ITO surface was also removed by Ar+ sputtering, it was accompanied by the removal of oxygen from ITO, and the work function was reduced (4.3 eV). Three factors, i.e.,: (i) C-containing contaminants, (ii) the O/In ratio, and (iii) the In/Sn ratio on the ITO surface affect the work function. The present results and those of other workers suggest that these three factors affect the work function in the order: (ii)>(i)>(iii), and (i) is the main cause of the increase in the work function in the UV–ozone or O2 plasma treatments. © 2000 American Institute of Physics.
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73.30.+y Surface double layers, Schottky barriers, and work functions
81.65.Cf Surface cleaning, etching, patterning
68.35.Dv Composition, segregation; defects and impurities
79.60.Bm Clean metal, semiconductor, and insulator surfaces
43.35.Zc Use of ultrasonics in nondestructive testing, industrial processes, and industrial products
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
85.60.Jb Light-emitting devices

Magnetoresistance of constricted ferromagnetic wires

A. O. Adeyeye, R. P. Cowburn, and M. E. Welland

J. Appl. Phys. 87, 299 (2000); http://dx.doi.org/10.1063/1.371860 (4 pages) | Cited 7 times

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We describe a systematic study of magnetoresistance (MR) behavior of individual constricted 25 nm thick Ni80Fe20 wires. The structures consist of a 5 μm support and a narrow wire with width w in the range 100–500 nm. When the field is applied parallel to the wire axis, we observe two switching fields (for w⩽200 nm) corresponding to the distinct coercive fields of the narrow part of the wire and the 5 μm support structure, as compared to one switching field observed for w=500 nm. The MR response to the field applied perpendicular to the wire width is found to be very sensitive to w due to the demagnetizing field. We are able to deduce from the field sequence measurements the spin orientations in the fabricated structures. We have shown that it is possible to laterally control spin orientation for tailor made magnetic devices. © 2000 American Institute of Physics.
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72.15.Gd Galvanomagnetic and other magnetotransport effects
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Bb Fe and its alloys

Improved algorithm for modeling collision broadening through a sequence of scattering events in semiclassical Monte Carlo

Leonard F. Register and Karl Hess

J. Appl. Phys. 87, 303 (2000); http://dx.doi.org/10.1063/1.371861 (9 pages) | Cited 4 times

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An improved, more physically accurate algorithm is presented for modeling collision broadening in semiclassical Monte Carlo. More specifically, the method of connecting a sequence of collision broadened scattering events is addressed. Sequences of collision broadened scattering events are analyzed via basic theory and illustrated via first-principles simulations using the quantum transport simulator Schrödinger Equation Monte Carlo in which, in contrast to semiclassical Monte Carlo, real scattering and collision broadening are inseparable processes. It is demonstrated that the requirement for energy conservation in the coupled carrier-phonon system prohibits the accumulation of the uncertainty in the carrier energy associated with collision broadening through a sequence of scattering events, accumulation that is possible with the conventional treatment of collision broadening in semiclassical Monte Carlo. Based on this analysis, basic changes to the treatment of collision broadening in semiclassical Monte Carlo are suggested. The potential significance of these changes is then assessed via simplified semiclassical Monte Carlo simulations. In particular, the exaggeration of the high-energy tail of the carrier distribution possible with the conventional treatment of collision broadening in semiclassical Monte Carlo is demonstrated to be an artifact of the above described nonphysical accumulation of the collision broadening contributions, not of the form of the collision broadening used (Lorentzian, etc.) as often assumed; with this more physically accurate new algorithm, well-behaved high-energy tails of the carrier distribution are obtained even with full Lorentzian broadening. © 2000 American Institute of Physics.
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72.20.Ht High-field and nonlinear effects
72.10.Bg General formulation of transport theory

Charge transport in a blue-emitting alternating block copolymer with a small spacer to conjugated segment length ratio

Dongge Ma, I. A. Hümmelgen, Xiabin Jing, Zhiyong Hong, Lixiang Wang, Xiaojiang Zhao, Fosong Wang, and F. E. Karasz

J. Appl. Phys. 87, 312 (2000); http://dx.doi.org/10.1063/1.371862 (5 pages) | Cited 28 times

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We analyze current versus voltage data obtained using single carrier injection in several metal/polymer/metal sandwich structures. The polymer used in each case is a soluble blue-emitting alternating block copolymer. Our experimental results demonstrate that the electron transport is space-charge limited by the high density of traps having an exponential energy distribution (temperature dependent characteristic energy) in the copolymer. The electron mobility of 8×10−10 cm2/V s is directly determined using space-charge-limited current analytical expressions. Hole transport is also space-charge limited, with a mobility of 2×10−6 cm2/V s. A hole trap with energy 0.17 eV is observed. We compare these results with those obtained for related block copolymers with different spacer and conjugated segment lengths and discuss the influence of spacer length and conjugated segment length on the charge transport properties. © 2000 American Institute of Physics.
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73.40.Sx Metal-semiconductor-metal structures
72.20.Fr Low-field transport and mobility; piezoresistance
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Le Polymers; organic compounds (including organic semiconductors)
72.20.Ht High-field and nonlinear effects

Thermoelectric properties of pure and doped FeMSb (M=V,Nb)

D. P. Young, P. Khalifah, R. J. Cava, and A. P. Ramirez

J. Appl. Phys. 87, 317 (2000); http://dx.doi.org/10.1063/1.371863 (5 pages) | Cited 24 times

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The thermoelectric properties of the pure and doped half-Heusler compounds FeVSb and FeNbSb are reported. The electrical resistivities are between 0.2 and 20 mΩ cm at room temperature. Thermoelectric power measurements indicate that FeVSb is an n-type material with moderate Seebeck coefficients near −70 μV/K at 300 K. The thermal conductivity at room temperature is large, approximately 0.1 W/cm K, and increases with decreasing temperature. Chemical substitutions, which have a dramatic effect on the transport properties, were performed in an effort to enhance the thermoelectric performance. Band-structure calculations are presented for the pure materials. © 2000 American Institute of Physics.
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72.15.Jf Thermoelectric and thermomagnetic effects
71.20.Be Transition metals and alloys

Time-resolved photocurrent and electric field measurements in high resistivity CdTe

G. Ghislotti, S. Pietralunga, L. Ripamonti, R. Sacco, S. Micheletti, and F. Bosisio

J. Appl. Phys. 87, 322 (2000); http://dx.doi.org/10.1063/1.371864 (7 pages) | Cited 3 times

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We studied current and electric field transients in high resistivity CdTe:In crystals by means of nanosecond time-resolved photocurrent and electro-optic sampling measurements. Electron and hole dynamics have been investigated for different excitation regimes (incident photon fluence and wavelength). A numerical solution for a drift-diffusion model in presence of several defect centers is given which allows to interpret experimental results. Current decay can be described by two time constants of about 10 and 100 ns, the first one being predominant for low incident photon energy (<1 eV). By comparison with the numerical model, the fast and slow time constants are related to hole and electron trapping, respectively. Electric field decays in a millisecond time scale. This is related to charge trapped in a deep recombination center located at 0.75 eV from the conduction band. © 2000 American Institute of Physics.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.47.-p Spectroscopy of solid state dynamics
72.80.Ey III-V and II-VI semiconductors
72.40.+w Photoconduction and photovoltaic effects
71.55.Gs II-VI semiconductors
78.20.Jq Electro-optical effects

Monte Carlo method for the investigation of electron diffusion in degenerate semiconductors

P. Borowik and J. L. Thobel

J. Appl. Phys. 87, 329 (2000); http://dx.doi.org/10.1063/1.371865 (5 pages) | Cited 1 time

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We propose an efficient Monte Carlo method for calculating diffusion coefficients in degenerate semiconductors by simulating two populations of particles: one obeying the nonlinear Boltzmann equation and the other obeying the linearized Boltzmann equation. The required numbers of particles and observation times are very different for the two populations. With the aim of improving computing efficiency, we have developed a rejection technique in order to account for the coupling between the two populations. We apply this method to the study of highly degenerate GaAs. We compare diffusivity and noise spectral density in order to investigate the noise reduction induced by degeneracy. We find that the magnitude of this effect is strongly sensitive to the applied field. We also suggest a possible application of our method to the accurate determination of low-field mobility. © 2000 American Institute of Physics.
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72.20.Fr Low-field transport and mobility; piezoresistance
72.20.Ht High-field and nonlinear effects
72.80.Ey III-V and II-VI semiconductors
02.50.Ng Distribution theory and Monte Carlo studies
02.70.Rr General statistical methods
72.70.+m Noise processes and phenomena

Two dimensional electron gases induced by spontaneous and piezoelectric polarization in undoped and doped AlGaN/GaN heterostructures

O. Ambacher, B. Foutz, J. Smart, J. R. Shealy, N. G. Weimann, K. Chu, M. Murphy, A. J. Sierakowski, W. J. Schaff, L. F. Eastman, R. Dimitrov, A. Mitchell, and M. Stutzmann

J. Appl. Phys. 87, 334 (2000); http://dx.doi.org/10.1063/1.371866 (11 pages) | Cited 33 times

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Two dimensional electron gases in AlxGa1−xN/GaN based heterostructures, suitable for high electron mobility transistors, are induced by strong polarization effects. The sheet carrier concentration and the confinement of the two dimensional electron gases located close to the AlGaN/GaN interface are sensitive to a large number of different physical properties such as polarity, alloy composition, strain, thickness, and doping of the AlGaN barrier. We have investigated these physical properties for undoped and silicon doped transistor structures by a combination of high resolution x-ray diffraction, atomic force microscopy, Hall effect, and capacitance–voltage profiling measurements. The polarization induced sheet charge bound at the AlGaN/GaN interfaces was calculated from different sets of piezoelectric constants available in the literature. The sheet carrier concentration induced by polarization charges was determined self-consistently from a coupled Schrödinger and Poisson equation solver for pseudomorphically and partially relaxed barriers with different alloy compositions. By comparison of theoretical and experimental results, we demonstrate that the formation of two dimensional electron gases in undoped and doped AlGaN/GaN structures rely both on piezoelectric and spontaneous polarization induced effects. In addition, mechanisms reducing the sheet carrier concentrations like nonabrupt interfaces, dislocations, and the possible influence of surface states on the two dimensional electron gases will be discussed briefly. © 2000 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
77.65.-j Piezoelectricity and electromechanical effects
77.22.Ej Polarization and depolarization
85.30.Tv Field effect devices
72.20.My Galvanomagnetic and other magnetotransport effects
61.72.Lk Linear defects: dislocations, disclinations

Temperature behavior of multiple tunnel junction devices based on disordered dot arrays

A. S. Cordan, Y. Leroy, A. Goltzené, A. Pépin, C. Vieu, M. Mejias, and H. Launois

J. Appl. Phys. 87, 345 (2000); http://dx.doi.org/10.1063/1.371867 (8 pages) | Cited 29 times

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Nanometer-sized multijunction arrays are expected to exhibit a large Coulomb blockade effect. However, up to now, only highly disordered arrays can be fabricated. In this article, we evaluate the consequences of disorder on the dispersion of the device characteristics. We show that, as observed for regular arrays, the threshold voltage Vth increases with the length of the multijunction array. At very low temperature, the Vth dispersion is small. Conversely, at higher temperature, a large dispersion in Vth is observed. We evidence the importance of the different array parameters with respect to the device characteristics. We show that the crucial parameters are the tunnel resistances and, therefore, for a two-dimensional array, the total resistance of the minimal resistance path is the most relevant parameter. © 2000 American Institute of Physics.
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73.23.Hk Coulomb blockade; single-electron tunneling

Comparison of zinc-blende and wurtzite GaN semiconductors with spontaneous polarization and piezoelectric field effects

Seoung-Hwan Park and Shun-Lien Chuang

J. Appl. Phys. 87, 353 (2000); http://dx.doi.org/10.1063/1.371915 (12 pages) | Cited 82 times

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The electronic properties of (001)-, (111)-oriented zinc-blende and (0001)-oriented wurtzite crystals are investigated theoretically, where the spontaneous polarization and piezoelectric (PZ) field effects are taken into account. We show that the Luttinger–Kohn 6×6 Hamiltonians for the valence bands of the zinc-blende crystals written in the wurtzite bases for (001) and (111) crystal orientations and the Hamiltonian for the (0001)-orientation of wurtzite crystals can all be block diagonalized to two 3×3 Hamiltonians, which have analytical solutions for eigenvalues and eigenvectors. We then derive analytical expressions for the strain dependent band-edge effective masses and interband optical matrix elements of zinc-blende and wurtzite GaN crystals and compare their numerical results as well as valence band structures. Although the compressively strained zinc-blende quantum wells in materials such as GaAs- and ZnSe-based systems show reduced threshold carrier densities due to the lower in-plane effective mass, we find that for GaN the reduction of the effective mass with the biaxial compressive strain is not significant in both zinc-blende and wurtzite structures. An alternative method is the application of a uniaxial strain to reduce the in-plane effective masses in both structures. It is also found that the valence band structures and the overlap integral of the electron and hole wave functions of GaN/AlGaN quantum-well structures are affected significantly by the PZ field for (111) zinc-blende structures and by both the spontaneous polarization and PZ fields for (0001) wurtzite structures. © 2000 American Institute of Physics.
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71.20.Nr Semiconductor compounds
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
77.65.Ly Strain-induced piezoelectric fields

Microstructure and electrical resistivity of Cu and Cu3Ge thin films on Si1−xGex alloy layers

M. O. Aboelfotoh, M. A. Borek, and J. Narayan

J. Appl. Phys. 87, 365 (2000); http://dx.doi.org/10.1063/1.371868 (4 pages) | Cited 4 times

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We have studied the reaction between Cu and ϵ1-Cu3Ge thin films and Si1−xGex (x=0.5) alloy layers epitaxially grown on Si(100) in the temperature range of 250–400 °C. In this temperature range, Cu reacts with the alloy to form a Cu3Si1−xGex ternary phase with an ordered body-centered-cubic crystal structure, and no Ge segregation occurs during the reaction. Unlike ϵ1-Cu3Ge, the Cu3Si1−xGex films exhibit a high-room-temperature resistivity of ∼150 μΩ cm. However, the Cu3Si1−xGex phase is not observed when Ge is added to Cu to form ϵ1-Cu3Ge. In contrast to the results reported for films of ϵ1-Cu3Ge formed on Si(100) substrates, the outdiffusion of Si into the ϵ1-Cu3Ge films is found to be suppressed when the films are formed on Si0.5Ge0.5 layers at temperatures up to 500 °C, and their resistivity remains low (typically less than 10 μΩ cm at room temperature), indicating the increased stability of ϵ1-Cu3Ge on Si1−xGex alloys. Furthermore, the ϵ1-Cu3Ge films form a sharp interface with the Si0.5Ge0.5 layers. These results indicate that ϵ1-Cu3Ge is an attractive candidate for contacts to SiGe-based devices. © 2000 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
68.55.-a Thin film structure and morphology
73.61.At Metal and metallic alloys

Characterization of an AlGaN/GaN two-dimensional electron gas structure

A. Saxler, P. Debray, R. Perrin, S. Elhamri, W. C. Mitchel, C. R. Elsass, I. P. Smorchkova, B. Heying, E. Haus, P. Fini, J. P. Ibbetson, S. Keller, P. M. Petroff, S. P. DenBaars, U. K. Mishra, et al.

J. Appl. Phys. 87, 369 (2000); http://dx.doi.org/10.1063/1.371869 (6 pages) | Cited 36 times

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An AlxGa1−xN/GaN two-dimensional electron gas structure with x=0.13 deposited by molecular beam epitaxy on a GaN layer grown by organometallic vapor phase epitaxy on a sapphire substrate was characterized. X-ray diffraction maps of asymmetric reciprocal lattice points confirmed that the thin AlGaN layer was coherently strained to the thick GaN layer. Methods for computing the aluminum mole fraction in the AlGaN layer by x-ray diffraction are discussed. Hall effect measurements gave a sheet electron concentration of 5.1×1012 cm−2 and a mobility of 1.9×104 cm2/V s at 10 K. Mobility spectrum analysis showed single-carrier transport and negligible parallel conduction at low temperatures. The sheet carrier concentrations determined from Shubnikov–de Haas magnetoresistance oscillations were in good agreement with the Hall data. The electron effective mass was determined to be 0.215±0.006 m0 based on the temperature dependence of the amplitude of Shubnikov–de Haas oscillations. The quantum lifetime was about one-fifth of the transport lifetime of 2.3×10−12 s. © 2000 American Institute of Physics.
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73.61.Ey III-V semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
68.35.Ct Interface structure and roughness
72.20.Ee Mobility edges; hopping transport
72.20.My Galvanomagnetic and other magnetotransport effects
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

Photoemission study of aluminum/tris-(8-hydroxyquinoline) aluminum and aluminum/LiF/tris-(8-hydroxyquinoline) aluminum interfaces

Quoc Toan Le, Li Yan, Yongli Gao, M. G. Mason, D. J. Giesen, and C. W. Tang

J. Appl. Phys. 87, 375 (2000); http://dx.doi.org/10.1063/1.371870 (5 pages) | Cited 116 times

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We have investigated the interfaces of aluminum on tris-(8-hydroxyquinoline) aluminum (Alq3) and aluminum on LiF/Alq3, using x-ray and ultraviolet photoemission spectroscopy (UPS). Aluminum appears to react destructively with Alq3 causing significant modification of the oxygen, nitrogen, and aluminum spectra. The well-defined UPS spectrum of Alq3 is quickly destroyed by very low coverages of aluminum. With only a 5 Å layer of LiF on the Alq3, the reaction with aluminum is significantly suppressed. The Alq3 molecular orbital features in the UPS shift to higher binding energy but remain easily recognizable. In addition, a well-defined gap-state forms which is significantly different from that produced without LiF. Both the core-level spectra and the gap-state suggest that the Alq3 anion is formed in the presence of aluminum and LiF. © 2000 American Institute of Physics.
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85.60.Jb Light-emitting devices
73.61.Ph Polymers; organic compounds
78.66.Qn Polymers; organic compounds
79.60.Fr Polymers; organic compounds
79.60.Dp Adsorbed layers and thin films
73.20.At Surface states, band structure, electron density of states

Cr/Al and Cr/Al/Ni/Au ohmic contacts to n-type GaN

N. A. Papanicolaou, A. Edwards, M. V. Rao, J. Mittereder, and W. T. Anderson

J. Appl. Phys. 87, 380 (2000); http://dx.doi.org/10.1063/1.371871 (7 pages) | Cited 18 times

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In this work we investigate the performance of Cr/Al and Cr/Al/Ni/Au ohmic contacts on n-type GaN. Annealing of the contacts was achieved by using a low temperature conventional quartz tube furnace in an Ar ambient and a new vacuum annealing technique using a tungsten strip heater. Low specific contact resistivity (ρc) metallizations were achieved with furnace annealing at considerably lower temperatures (550–600 °C)than those typically required for GaN contacts by halogen lamp rapid thermal annealing (∼900 °C). Vacuum annealing was found to require temperatures similar to those used in halogen lamp rapid thermal annealing for forming ohmic contacts on n-type GaN, but with minimal oxidation of the Al surface. For the Cr/Al bilayer on GaN with n doping of 1018 cm−3, minimum specific contact resistivities of 1.6×10−4 Ω cm2 and 2.3×10−5 Ωcm2 were achieved for furnace annealing and vacuum annealing, respectively. Our experiments showed that, when Cr was used as a contact material, the simultaneous presence of Cr and Al was necessary in order to obtain the best possible ohmic properties. Furthermore, the Cr/Al contacts maintained good stability at elevated temperatures. The Cr/Al/Ni/Au system offers lower ρc values and even greater temperature stability than the Cr/Al system when annealed in the 800–1200 °C temperature range. Atomic force microscopy investigations indicated that the introduction of the Ni/Au overlayer had the effect of increasing the surface roughness after annealing. © 2000 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
73.40.Cg Contact resistance, contact potential
81.40.Gh Other heat and thermomechanical treatments
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.40.Rs Electrical and magnetic properties related to treatment conditions
61.72.Cc Kinetics of defect formation and annealing

Spin-polarized electronic current in resonant tunneling heterostructures

A. Voskoboynikov, Shiue Shin Lin, C. P. Lee, and O. Tretyak

J. Appl. Phys. 87, 387 (2000); http://dx.doi.org/10.1063/1.371872 (5 pages) | Cited 67 times

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The spin-dependent tunneling phenomenon in symmetric and asymmetric resonant semiconductor heterostructures is employed in a theoretical study to investigate the output tunnel current polarization at zero magnetic field. A simple model of the resonant tunneling structures and a simple one-electron band approximation with spin-orbit interaction are used in this work. It is shown that asymmetry in the electron distribution at the electrode regions provides spin-polarized tunnel current. An approach to optimize this spin-dependent effect is explored theoretically. In asymmetric resonant tunneling structures, we estimate theoretically that the polarization can reach 40% with a moderate applied electric field. © 2000 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.40.Gk Tunneling
73.23.-b Electronic transport in mesoscopic systems
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
71.15.-m Methods of electronic structure calculations
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