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24 May 1999

Volume 74, Issue 21, pp. 3081-3230

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Enhanced photoluminescence in epitaxial ZnGa2O4:Mn thin-film phosphors using pulsed-laser deposition

Yong Eui Lee, David P. Norton, and John D. Budai

Appl. Phys. Lett. 74, 3155 (1999); http://dx.doi.org/10.1063/1.124095 (3 pages) | Cited 42 times

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The growth and properties of ZnGa2O4:Mn thin-film phosphors on single crystal substrates using pulsed-laser deposition were investigated. Epitaxial film properties were compared to polycrystalline films deposited on glass substrates. Green photoluminescence was observed for as-deposited films with no postannealing required. Enhanced luminescent intensity in the epitaxial films was observed as compared to randomly oriented polycrystalline films, suggesting that grain boundaries and grain alignment strongly influence the luminescent properties. The ratio of Zn/Ga in the films also affected photoluminescence properties, with strong green emission observed in Zn-deficient films. © 1999 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
78.66.Li Other semiconductors
81.15.Fg Pulsed laser ablation deposition
81.05.Hd Other semiconductors
68.55.-a Thin film structure and morphology
68.55.Nq Composition and phase identification

Temperature dependence of far-infrared electroluminescence in parabolic quantum wells

J. Ulrich, R. Zobl, K. Unterrainer, G. Strasser, E. Gornik, K. D. Maranowski, and A. C. Gossard

Appl. Phys. Lett. 74, 3158 (1999); http://dx.doi.org/10.1063/1.124091 (3 pages) | Cited 15 times

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We have measured the far-infrared emission from parabolically graded quantum wells driven by an in-plane electric field in the temperature range from 20 to 240 K. The peak emission corresponds to the intersubband plasmon in the parabolic potential. Its photon energy (6.6/9.8 meV) remains rather unaffected by temperature variations, the full-width at half-maximum ranges from 1 (T=20 K) to 2 meV (T=240 K). The reduction of emission efficiency with increasing temperature is attributed to the change in the nonradiative lifetime. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.60.Fi Electroluminescence
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Inversion of surface composition and evolution of nanostructure in Cu/Co nanocrystals

A. S. Edelstein, V. G. Harris, D. R. Rolison, L. Kurihara, David J. Smith, J. Perepezko, and M. H. da Silva Bassani

Appl. Phys. Lett. 74, 3161 (1999); http://dx.doi.org/10.1063/1.124087 (3 pages) | Cited 8 times

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Nanocrystals of Cu/Co with a nearly pure Cu core and a Co-rich shell have been chemically synthesized. This structure results from reaction kinetics and represents an inversion of surface composition since the surface energy of Co is larger than that of Cu. Both the Cu core and the Co-rich shell initially have an fcc structure and a common lattice constant. Annealing at temperatures in the range of 300 to 600 °C causes the material to phase separate, forming small, increasingly pure Co nanocrystals which aggregate on the surface of the pure Cu nanocrystals. © 1999 American Institute of Physics.
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68.35.Dv Composition, segregation; defects and impurities
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.35.Md Surface thermodynamics, surface energies
61.46.-w Structure of nanoscale materials
61.72.Cc Kinetics of defect formation and annealing
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Tailorable, visible light emission from silicon nanocrystals

J. P. Wilcoxon and G. A. Samara

Appl. Phys. Lett. 74, 3164 (1999); http://dx.doi.org/10.1063/1.124096 (3 pages) | Cited 72 times

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Crystalline, size-selected Si nanocrystals in the size range 1.8–10 nm grown in inverse micellar cages exhibit highly structured optical absorption and photoluminescence (PL) across the visible range of the spectrum. The most intense PL for the smallest nanocrystals produced (∼2 nm) was in the blue (∼365 nm) with a radiative lifetime of ∼1 ns and is attributed to direct recombination at zone center. © 1999 American Institute of Physics.
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78.55.Ap Elemental semiconductors
78.66.Db Elemental semiconductors and insulators
78.66.Vs Fine-particle systems
78.40.Fy Semiconductors

Negative capacitance of GaAs homojunction far-infrared detectors

A. G. U. Perera, W. Z. Shen, M. Ershov, H. C. Liu, M. Buchanan, and W. J. Schaff

Appl. Phys. Lett. 74, 3167 (1999); http://dx.doi.org/10.1063/1.124169 (3 pages) | Cited 27 times

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Bias, frequency and temperature-dependent capacitance characteristics of p-GaAs homojunction interfacial work-function internal photoemission (HIWIP) far-infrared detectors are reported. A strong negative capacitance phenomenon has been observed. Unlike in other devices, even up to 1 MHz in HIWIP, the negative capacitance value keeps increasing with frequency, giving a stronger effect. The origin of this effect is believed to be due to the carrier capture and emission at interface states. Fitting data based on charging-discharging current and the inertial conducting current model show good agreement with the experimental observations. © 1999 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.20.-r Electron states at surfaces and interfaces
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Stable dynamic avalanche in Si power diodes

Martin Domeij, Bo Breitholtz, Mikael Östling, and Josef Lutz

Appl. Phys. Lett. 74, 3170 (1999); http://dx.doi.org/10.1063/1.124097 (3 pages) | Cited 4 times

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A stable dynamic avalanche at a maximum power density of about 2.4 MW/cm2 was measured in small areas of 3.3 kV Si power diodes, using an optical measurement technique, and very good dynamic ruggedness was verified in a conventional turn-off measurement. Device simulations of a diode with a shallow n+ emitter indicate that impact ionization at the nn+ junction can result in negative differential resistance (NDR) and current filamentation, whereas a deep n+ emitter in the experimentally studied diode suppresses NDR. It is, therefore, proposed that the deep n+ emitter is important for the stable dynamic avalanche. © 1999 American Institute of Physics.
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85.30.Kk Junction diodes
85.30.De Semiconductor-device characterization, design, and modeling
84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables

Plasma process-induced band-gap modifications of a strained SiGe heterostructure

P. K. Swain, S. Madapur, and D. Misra

Appl. Phys. Lett. 74, 3173 (1999); http://dx.doi.org/10.1063/1.124098 (3 pages) | Cited 5 times

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Exposure to plasma etching and subsequent annealing can relax the strain of coherently strained SiGe. This work investigates the change in valence-band discontinuity in plasma-exposed SiGe films due to strain relaxation by a capacitance–voltage (C–V) profiling technique using metal–oxide–semiconductor structures. Dry and wet etched samples annealed at 500, 600, 700, and 800 °C were investigated. Valence-band discontinuity ΔEV at the Si/SiGe interface reduced with annealing temperature and completely disappeared at higher temperature annealing. Dry etched samples demonstrated a faster relaxation mechanism as compared to their wet etched counterparts. The C–V method has turned out to be a simple, fast, and efficient approach to estimate any band-gap modifications in SiGe due to process-induced damage. © 1999 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.65.Cf Surface cleaning, etching, patterning
68.60.Bs Mechanical and acoustical properties
71.20.Ps Other inorganic compounds
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances
61.72.Cc Kinetics of defect formation and annealing
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.05.Hd Other semiconductors

In situ growth of an epitaxial CoSi2 layer on a Si (100) substrate by reactive chemical-vapor deposition using a cobalt metallorganic source

Hwa Sung Rhee and Byung Tae Ahn

Appl. Phys. Lett. 74, 3176 (1999); http://dx.doi.org/10.1063/1.124067 (3 pages) | Cited 15 times

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Uniform epitaxial CoSi2 layers have been grown in situ on a (100) Si substrate at temperatures above 600 °C by reactive chemical-vapor deposition of cyclopentadienyl dicarbonyl cobalt, Co(η5-C5H5)(CO)2. Co-rich phases such as Co2Si and CoSi were suppressed during cobalt metallorganic chemical-vapor deposition at substrate temperatures above 500 °C. A thin carbon layer was found on the top of the epitaxial CoSi2 layer grown on the Si substrate due to incomplete decomposition of the cobalt metallorganic source and diffusion of Co into the Si substrate. In spite of the existence of a surface carbon layer, an ion channeling minimum yield, χmin, of 8% in Rutherford backscattering/channeling spectrometry has been achieved in the epitaxial layer, indicating a nearly perfect epitaxial order. The carbon pileup on the surface of the CoSi2 layer at the initial stage of Co deposition seems to play the role of a cobalt diffusion barrier, avoiding the formation of Co-rich phases. © 1999 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.-a Thin film structure and morphology
85.40.Ls Metallization, contacts, interconnects; device isolation
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
82.80.Yc Rutherford backscattering (RBS), and other methods of chemical analysis

Acoustic driving effect on radiative decays of excitons in ZnSe/ZnS single quantum wells

O. A. Korotchenkov, A. Yamamoto, T. Goto, M.-W. Cho, and T. Yao

Appl. Phys. Lett. 74, 3179 (1999); http://dx.doi.org/10.1063/1.124099 (3 pages) | Cited 3 times

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We report that acoustic driving of ZnSe/ZnS quantum wells can yield ≥ 30% shortening of the fast component (on the order of 102 ps) of exciton radiative decays and relatively enhanced tail emissions at greater instants. The shortening is attributed to the driving-induced relocalization of excitons to lower-energy states while the enhancement is indicative of the drift diffusion of mobile populations in the driving electric field. These results suggest that the radiative recombination predominantly occurs from localized excitons. © 1999 American Institute of Physics.
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78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
71.35.-y Excitons and related phenomena
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
81.05.Dz II-VI semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.20.Fz Weak or Anderson localization
68.35.Gy Mechanical properties; surface strains

Growth of cubic GaN by phosphorus-mediated molecular beam epitaxy

Y. Zhao, C. W. Tu, I.-T. Bae, and T.-Y. Seong

Appl. Phys. Lett. 74, 3182 (1999); http://dx.doi.org/10.1063/1.124100 (3 pages) | Cited 10 times

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GaN epitaxial layers were grown on wurtzite GaN-on-sapphire substrates by phosphorus-mediated molecular beam epitaxy at different growth temperatures. The films were characterized by reflection high-energy electron diffraction, x-ray diffraction, energy-dispersive x-ray spectroscopy, and transmission electron microscopy. The growth temperature plays an important role in P incorporation as well as GaN crystallization. The introduction of the phosphorus flux during growth leads to a preferential growth of zinc-blende epilayers. The phase transition during growth is attributed to the modification of surface stoichiometry by the impinging phosphorus flux. © 1999 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
68.35.Rh Phase transitions and critical phenomena

Reactive ion etch-induced effects on the near-band-edge luminescence in GaN

R. Cheung, S. Withanage, R. J. Reeves, S. A. Brown, I. Ben-Yaacov, C. Kirchner, and M. Kamp

Appl. Phys. Lett. 74, 3185 (1999); http://dx.doi.org/10.1063/1.124101 (3 pages) | Cited 15 times

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GaN grown on c-plane sapphire substrates has been reactive ion etched successfully in a SF6 plasma with an etch rate of 29 nm/min. The etch rate does not change with substrate temperatures between 10 and 50 °C. Optical transitions have not been destroyed after etching, instead, two additional lower energy transitions appear close to the band-edge luminescence. The two additional transitions are related to defect states that bind excitons. The defect-bound states exhibit different behavior compared to the free excitonic states in that their normalized intensities decrease more rapidly as temperature increases, the peaks exist only up to 80 K, and their line energies show no temperature dependence. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
81.05.Ea III-V semiconductors
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
71.55.Eq III-V semiconductors
71.35.Cc Intrinsic properties of excitons; optical absorption spectra

Linear optical properties of a heavily Mg-doped Al0.09Ga0.91N epitaxial layer

M. J. Bergmann, Ü. Özgür, H. C. Casey, J. F. Muth, Y. C. Chang, R. M. Kolbas, R. A. Rao, C. B. Eom, and M. Schurman

Appl. Phys. Lett. 74, 3188 (1999); http://dx.doi.org/10.1063/1.124102 (3 pages) | Cited 1 time

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The room-temperature absorption coefficient and ordinary refractive index for a ∼0.4-μm-thick p-type wurtzite Al0.09Ga0.91N epitaxial layer were determined via optical transmission measurements. The layer was grown by metal organic chemical vapor deposition and heavily doped ( ∼ 5×1019 cm−3) with Mg. Additional measurements of the refractive index by prism coupling to the layer confirmed the transmission results. The low-temperature AlN buffer layer altered the expected interference fringes of the transmission spectrum below the band-gap energy and had to be accounted for in the analysis. The absorption coefficient exhibited band-tail effects and had a reduced slope near band-gap energy as compared to undoped GaN. Using a detailed balance argument, the reduced slope was consistent with the lack of a peak in the continuous-wave photoluminescent emission. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.40.Fy Semiconductors
71.20.Nr Semiconductor compounds
71.55.Eq III-V semiconductors
78.55.Cr III-V semiconductors

Domain configuration in pulsed laser deposited films of rhombohedral PbZr0.65Ti0.35O3

M. Tyunina, J. Wittborn, K. V. Rao, J. Levoska, S. Leppävuori, and A. Sternberg

Appl. Phys. Lett. 74, 3191 (1999); http://dx.doi.org/10.1063/1.124103 (3 pages) | Cited 8 times

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Highly oriented perovskite ferroelectric films of rhombohedral PbZr0.65Ti0.35O3, with [001] direction normal to the substrate surface, have been produced by pulsed laser deposition on La0.5Sr0.5CoO3/MgO (100). The domains in the films were detected using atomic force microscopy, registering the electromechanical response of the films in the presence of a low ac field. We observe a direct correlation between domain configuration and the microstructural features in the as-deposited films. In the large (∼200 nm) grains, an ordered polydomain configuration with {100} domain boundaries and “puckering” of the top surface of the grains are observed. The smaller grains are found to be single domain. The observed domain configuration in our films is significantly different from the lamellar pattern reported recently. © 1999 American Institute of Physics.  
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.Dj Domain structure; hysteresis
68.55.-a Thin film structure and morphology
81.15.Fg Pulsed laser ablation deposition
77.55.-g Dielectric thin films
77.65.-j Piezoelectricity and electromechanical effects
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(Ba,Sr)TiO3 thin films with conducting perovskite electrodes for dynamic random access memory applications

B. Nagaraj, T. Sawhney, S. Perusse, S. Aggarwal, R. Ramesh, V. S. Kaushik, S. Zafar, R. E. Jones, J.-H. Lee, V. Balu, and J. Lee

Appl. Phys. Lett. 74, 3194 (1999); http://dx.doi.org/10.1063/1.124104 (3 pages) | Cited 34 times

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Interfaces and hence electrodes determine the performance of (Ba,Sr)TiO3 (BST) capacitors for ultralarge scale integration dynamic random access memories. Electrode materials forming a rectifying contact on BST drastically reduce the dielectric constant and hence the capacitance and charge storage density of the capacitor, when the dielectric thickness is reduced. This can limit the role of Pt as an electrode material for gigabit dynamic random access memories (DRAM). The conducting oxide, La0.5Sr0.5CoO3 (LSCO) with its perovskite structure, has structural and chemical compatibility with BST. Our results in LSCO/BST/LSCO capacitor show that the mechanism of conduction is not interface limited but predominantly bulk limited. A 75 nm BST film with LSCO electrodes shows a leakage current density of 1×10−7 A/cm2 at 1 V, 85 °C. The dielectric constant at 1 V, 105 Hz is 350, making LSCO a potential contact electrode for DRAM memories. © 1999 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
77.55.-g Dielectric thin films
84.32.Tt Capacitors
84.30.Sk Pulse and digital circuits
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
73.50.Fq High-field and nonlinear effects

Large etch-selectivity enhancement in the epitaxial liftoff of single-crystal LiNbO3 films

A. M. Radojevic, M. Levy, R. M. Osgood, A. Kumar, H. Bakhru, C. Tian, and C. Evans

Appl. Phys. Lett. 74, 3197 (1999); http://dx.doi.org/10.1063/1.124115 (3 pages) | Cited 30 times

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We report on a large etch selectivity enhancement in the epitaxial liftoff of He+-implanted single-crystal lithium niobate (LiNbO3) films upon rapid thermal annealing. A buried sacrificial layer is formed by ion implantation. Heat treatment is found to reduce the time needed for film detachment by a factor as large as 100. Implant damage and postanneal stress-induced etch selectivity become nearly independent of implantation energy upon annealing. Large (0.5×1 cm2) 5–10-μm-thick single-crystal LiNbO3 films of excellent quality are detached in just a matter of a few hours. © 1999 American Institute of Physics.
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81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.65.Cf Surface cleaning, etching, patterning
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
61.72.Cc Kinetics of defect formation and annealing
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Ms Insulators
61.72.up Other materials
61.80.Jh Ion radiation effects
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
85.40.Ry Impurity doping, diffusion and ion implantation technology
81.40.Gh Other heat and thermomechanical treatments
68.60.Dv Thermal stability; thermal effects

Pauli-blocking imaging of single strain-induced semiconductor quantum dots

C. Obermüller, A. Deisenrieder, G. Abstreiter, K. Karrai, S. Grosse, S. Manus, J. Feldmann, H. Lipsanen, M. Sopanen, and J. Ahopelto

Appl. Phys. Lett. 74, 3200 (1999); http://dx.doi.org/10.1063/1.124116 (3 pages) | Cited 13 times

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The photoluminescence (PL) of InP strained-induced quantum dots in a GaInAs/GaAs quantum well is measured at low temperature (4.2 K) using near-field scanning optical microscopy. The PL originating from the first three confined levels of eight individual dots is mapped out over an area of 1.4×1.4 μm. The spatial resolution of the PL of the lowest energy level is found to be limited to about 0.5 μm. In contrast, the mapping of the PL of the higher excited state shows a much improved spatial resolution of the order of 150 nm which is the instrument resolution. This effect is understood in terms of Pauli-blocking of the dot level filling. © 1999 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
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Electroluminescence of europium silicate thin film on silicon

Jifa Qi, Takahiro Matsumoto, Masanori Tanaka, and Yasuaki Masumoto

Appl. Phys. Lett. 74, 3203 (1999); http://dx.doi.org/10.1063/1.124105 (3 pages) | Cited 13 times

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We report an electroluminescent device fabricated by a europium silicate layer on a silicon substrate. The device exhibits uniform-intense white color electroluminescence with an external quantum efficiency about 0.1% at room temperature, a low operating threshold voltage (about 6 V) and a fast response to the modulation signal at the frequency of 1 MHz. © 1999 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
81.15.Cd Deposition by sputtering
78.66.Li Other semiconductors

Combined laser and atomic force microscope lithography on aluminum: Mask fabrication for nanoelectromechanical systems

G. Abadal, A. Boisen, Z. J. Davis, O. Hansen, and F. Grey

Appl. Phys. Lett. 74, 3206 (1999); http://dx.doi.org/10.1063/1.124106 (3 pages) | Cited 10 times

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A direct-write laser system and an atomic force microscope (AFM) are combined to modify thin layers of aluminum on an oxidized silicon substrate, in order to fabricate conducting and robust etch masks with submicron features. These masks are very well suited for the production of nanoelectromechanical systems (NEMS) by reactive ion etching. In particular, the laser-modified areas can be subsequently locally oxidized by AFM and the oxidized regions can be selectively removed by chemical etching. This provides a straightforward means to define the overall conducting structure of a device by laser writing, and to perform submicron modifications by AFM oxidation. The mask fabrication for a nanoscale suspended resonator bridge is used to illustrate the advantages of this combined technique for NEMS. © 1999 American Institute of Physics.
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07.10.Cm Micromechanical devices and systems
85.40.Hp Lithography, masks and pattern transfer
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
07.79.Lh Atomic force microscopes
81.65.Cf Surface cleaning, etching, patterning
81.65.Mq Oxidation

Interface engineering in preparation of organic surface-emitting diodes

L. S. Hung and C. W. Tang

Appl. Phys. Lett. 74, 3209 (1999); http://dx.doi.org/10.1063/1.124107 (3 pages) | Cited 83 times

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Surface-emitting organic light emitting diode (OLED) was prepared by sputter deposition of indium-tin-oxide on a buffered organic layer structure. Confirming a previous report, a thin film of copper phthalocyanine (CuPc) was found to be a useful buffer layer in preventing sputter damage to the OLED layer structure, particularly the underlying Alq emissive layer. However, the CuPc layer forms an electron-injection barrier with the Alq layer, resulting in increased electron-hole recombination in the nonemissive CuPc layer, and thus a substantial reduction in electroluminescence efficiency. Incorporation of Li at the CuPc/Alq interface was found to reduce the injection barrier at the interface and recover the overall device efficiency with good surface emission characteristics. © 1999 American Institute of Physics.
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85.60.Jb Light-emitting devices
81.15.Cd Deposition by sputtering
78.60.Fi Electroluminescence
78.66.Qn Polymers; organic compounds

Organic light-emitting diode with 20 lm/W efficiency using a triphenyldiamine side-group polymer as the hole transport layer

S. E. Shaheen, G. E. Jabbour, B. Kippelen, N. Peyghambarian, J. D. Anderson, S. R. Marder, N. R. Armstrong, E. Bellmann, and R. H. Grubbs

Appl. Phys. Lett. 74, 3212 (1999); http://dx.doi.org/10.1063/1.124108 (3 pages) | Cited 22 times

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We have used triphenyldiamine side-group polymers as hole transport layers in multilayer organic light-emitting diodes using 8-hydroxyquinoline aluminum (Alq3) as an emission layer. The device efficiency systematically increases as the ionization potential of the hole transport layer is shifted further from the work function of the indium–tin–oxide anode. We attribute this trend to better balance of hole and electron charges in the device. An optimized device consisting of a fluorinated version of the polymer as the hole transport layer, quinacridone doped Al as the emission layer, and a LiF/Al cathode results in a peak external luminous efficiency of 20 lm/W. © 1999 American Institute of Physics.
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85.60.Jb Light-emitting devices
73.61.Ph Polymers; organic compounds

A metal/insulator tunnel transistor with 16 nm channel length

Ryouta Sasajima, Kouji Fujimaru, and Hideki Matsumura

Appl. Phys. Lett. 74, 3215 (1999); http://dx.doi.org/10.1063/1.124109 (3 pages) | Cited 8 times

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A nanometer transistor, metal/insulator tunnel transistor (MITT), which consists of only metal and insulator is experimentally studied. In the MITT, the Fowler–Nordheim tunneling currents through an insulator in lateral metal/insulator/metal structure are controlled by changing a voltage at a gate electrode upon the middle insulator, due to variation of tunnel-barrier thickness at the insulator. It is demonstrated that the MITT with 16 nm channel length fabricated by conventional photolithography can operate similarly to the conventional metal/oxide/semiconductor field-effect transistor with on/off ratio of current larger than 105. The result indicates that the MITT is a promising candidate for future switching transistors in ultralarge scale integrated circuits. © 1999 American Institute of Physics.  
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85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
85.40.Hp Lithography, masks and pattern transfer
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
73.40.Rw Metal-insulator-metal structures

Determination of the mobility gap of microcrystalline silicon and of the band discontinuities at the amorphous/microcrystalline silicon interface using in situ Kelvin probe technique

S. Hamma and P. Roca i Cabarrocas

Appl. Phys. Lett. 74, 3218 (1999); http://dx.doi.org/10.1063/1.124110 (3 pages) | Cited 15 times

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A method to determine the mobility gap of thin films and the band discontinuities in heterojunctions is presented. It combines in situ contact potential measurements with dark conductivity activation energy measurements. The method is applied to determine the mobility gap of microcrystalline silicon (μc-Si:H) and the band discontinuities at the μc-Si:H/amorphous silicon (a-Si:H) interface. The mobility gap of μc-Si:H depends on its crystalline volume fraction and varies between 1.48 and 1.55 eV. The main band discontinuity occurs at the valence band side. The consequences of the band discontinuities on a-Si:H based solar cells using μc-Si:H doped layers are discussed. © 1999 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.61.Cw Elemental semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
72.20.Ee Mobility edges; hopping transport
73.20.-r Electron states at surfaces and interfaces
84.60.Jt Photoelectric conversion
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
73.40.Cg Contact resistance, contact potential

Raman characterization of SiNx deposition on undoped Al0.48In0.52As and n+ Ga0.47In0.53As layers for InP high electron mobility transistor applications

B. Boudart, C. Gaquière, S. Trassaert, M. Constant, A. Lorriaux, and N. Lefebvre

Appl. Phys. Lett. 74, 3221 (1999); http://dx.doi.org/10.1063/1.124111 (3 pages) | Cited 4 times

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Effects of SiNx deposition on undoped Al0.48In0.52As and n+ Ga0.47In0.53As bulk layers grown on InP substrate have been investigated using Raman spectroscopy. No significant effects induced from the dielectric deposition have been observed in the Al0.48In0.52As material, whatever the thickness and the temperature deposition used in the technological process. On the contrary, slight modifications of the Raman spectra have been noticed for n+ Ga0.47In0.53As samples passivated at 300 °C. The observed differences have been interpreted as a surface potential decrease of 0.15 V and correlated to electrical measurements made on InP-based high electron mobility transistors. In this case, an increase of the maximum drain current has been observed in agreement with the surface potential change deduced from Raman experiments. © 1999 American Institute of Physics.
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81.65.Rv Passivation
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.30.Tv Field effect devices
78.66.Fd III-V semiconductors
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
78.30.Fs III-V and II-VI semiconductors
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Ultrasonic characterization of plastic foams via measurements with static pressure variations

Christophe Ayrault, Alexei Moussatov, Bernard Castagnède, and Denis Lafarge

Appl. Phys. Lett. 74, 3224 (1999); http://dx.doi.org/10.1063/1.124112 (3 pages) | Cited 4 times

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A method for ultrasonic characterization of plastic foams by changing the static pressure of air that saturates the foam has been proposed. The method is based on high frequency asymptotic expressions of the standard Johnson–Allard equivalent fluid model. It is shown, both experimentally and theoretically, that the real part of squared acoustical refractive index and logarithm of the transmission coefficient depend linearly on the inverse of the square root of applied static pressure. These linear relations provide a simple and convenient way to determine experimentally the constitutive parameters. The method is illustrated with industrial open-cell foams. Advantages, limitations, and perspectives are discussed. © 1999 American Institute of Physics.
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43.35.-c Ultrasonics, quantum acoustics, and physical effects of sound
43.20.El Reflection, refraction, diffraction of acoustic waves
43.50.-x Noise: its effects and control
62.65.+k Acoustical properties of solids

Instant holography

P. S. Ramanujam, M. Pedersen, and S. Hvilsted

Appl. Phys. Lett. 74, 3227 (1999); http://dx.doi.org/10.1063/1.124113 (3 pages) | Cited 37 times

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Instant photography, epitomized by Polaroid films is characterized by the rapid appearance of an image after exposure. We describe here an instant off-axis holographic process, characterized by exposures as short as 5 ns and an instant display process, not requiring any wet chemical processing. The holograms are made in a side-chain azobenzene polyester and can be erased through a thermal treatment of the film enabling the film to be reused. Significantly, an atomic force microscopic scan of the film shows a strong surface relief after the 5 ns exposure paving the way for a cheap, mass replication of the holograms using a micromolding technique. © 1999 American Institute of Physics.
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42.40.Ht Hologram recording and readout methods
42.70.Ln Holographic recording materials; optical storage media
42.70.Jk Polymers and organics
42.40.Eq Holographic optical elements; holographic gratings
68.35.B- Structure of clean surfaces (and surface reconstruction)
42.79.Vb Optical storage systems, optical disks
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