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21 Apr 1997

Volume 70, Issue 16, pp. 2067-2203

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Polymeric anodes for improved polymer light-emitting diode performance

S. A. Carter, M. Angelopoulos, S. Karg, P. J. Brock, and J. C. Scott

Appl. Phys. Lett. 70, 2067 (1997); http://dx.doi.org/10.1063/1.118953 (3 pages) | Cited 188 times

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We have studied polyaniline and polyethylenedioxythiophene transparent electrodes for use as hole-injecting anodes in polymer light emitting diodes. The anodes were doped with a variety of polymer and monomer-based acids and cast from either water or organic solvents to determine the effect of the dopant and solvent on the hole-injection properties. We find that the anodes with polymeric dopants have improved device quantum efficiency and brightness relative to those with small molecule dopants, independent of conductivity, solvent, or type of conducting polymer. For the most conducting polymer anodes [σ>2(Ωcm)−1], diodes could be made without an indium tin oxide underlayer. These diodes show substantially slower degradation. © 1997 American Institute of Physics.
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85.60.Jb Light-emitting devices

Differential measurement of the coupling constant between laser eigenstates

M. Brunel, M. Vallet, A. Le Floch, and F. Bretenaker

Appl. Phys. Lett. 70, 2070 (1997); http://dx.doi.org/10.1063/1.118954 (3 pages) | Cited 12 times

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The possibility to measure the coupling constant C between eigenstates in a laser is demonstrated. Spatial separation of orthogonally polarized modes is shown to provide a simple differential tool to measure their coupling. The difference in the behaviors of linear and helicoidal eigenstates enlightens the influence of the nature of the eigenstates on their interaction in the active medium. The obtained experimental values are C = 0.16 for linear and C = 0.4 for helicoidal eigenstates in a longitudinally monomode Nd:YAG laser. The method is applicable to most kinds of laser. © 1997 American Institute of Physics.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.Fc Modulation, tuning, and mode locking

Dynamics of dual-wavelength emission from a coupled semiconductor microcavity laser

P. Michler, M. Hilpert, and G. Reiner

Appl. Phys. Lett. 70, 2073 (1997); http://dx.doi.org/10.1063/1.118955 (3 pages) | Cited 24 times

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We present an experimental demonstration of the dynamics of dual-wavelength emission from a coupled semiconductor microcavity laser after femtosecond optical excitation at 20 K. The coupled microcavity laser is comprised of two λ sized Al0.2Ga0.8As/Al0.5Ga0.5As cavities, separated by a common mirror. The bottom cavity contains three 10 nm thick GaAs quantum wells (QWs) whereas the top cavity contains three 16 nm thick GaAs QWs. Time-resolved measurements of the stimulated emission show pulses as short as 4.8 ps (10 ps) and peak delays as short as 13 ps (16 ps) for the shorter (longer) emission wavelength. Fast pulse fall times of 1 ps are observed for the pulses of the shorter emission wavelength which can be explained by the simultaneous interaction of the two photon modes with both gain regions of the two types of QWs. © 1997 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

High-index proton-exchanged waveguides in Z-cutLiNbO3 with undegraded nonlinear optical coefficients

J. Rams, J. Olivares, and J. M. Cabrera

Appl. Phys. Lett. 70, 2076 (1997); http://dx.doi.org/10.1063/1.118216 (3 pages) | Cited 9 times

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A method is described for producing high quality optical waveguides on Z-cut LiNbO3 substrates by proton exchange in pure benzoic acid vapor. Either α- or β-phase guides are obtained by varying the exchange temperature (within the 250–375 °C range) and/or the treatment duration (between 15 min and 24 h). The method presents definitive advantages with regards to common immersion methods. For both α- and β-phase guides the d33 nonlinear optical coefficient is 90% of the substrate value, and their optical losses are below 0.35 dB/cm. This is the first report on β-phase guides with almost undegraded nonlinear optical coefficients. © 1997 American Institute of Physics.
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42.65.Wi Nonlinear waveguides
42.79.Gn Optical waveguides and couplers
42.86.+b Optical workshop techniques
82.30.Hk Chemical exchanges (substitution, atom transfer, abstraction, disproportionation, and group exchange)

Planar optical waveguides fabricated by molecular beam epitaxy of Pb-doped CaF2 layers

G. Lifante, T. Balaji, and A. Muñoz-Yagüe

Appl. Phys. Lett. 70, 2079 (1997); http://dx.doi.org/10.1063/1.118956 (3 pages)

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Molecular beam epitaxy of rare-earth-doped CaF2 layers has already been demonstrated. Optical waveguiding can be obtained if the refractive index variation due to the rare-earth doping is high enough. To tailor separately the refractive index profile and the active ion profile in the layer, the former should be modified by a passive impurity. This letter demonstrates that passive waveguides can be obtained in CaF2 epitaxial layers by the introduction of moderate concentrations of Pb. Monomode planar waveguides with a steplike index variation ranging from 0.2% to 1.2% (relative to CaF2) have been grown and characterized, paving the way for the independent engineering of refractive index and active center distributions in optical active waveguide devices made of this kind of material. © 1997 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
42.86.+b Optical workshop techniques

Noncollinear four-wave mixing in a broad area semiconductor optical amplifier

Daniel X. Zhu, Serge Dubovitsky, William H. Steier, Kushant Uppal, Denis Tishinin, Johan Burger, and P. Daniel Dapkus

Appl. Phys. Lett. 70, 2082 (1997); http://dx.doi.org/10.1063/1.118957 (3 pages) | Cited 8 times

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A high-efficiency noncollinear four-wave mixing in a broad area traveling-wave semiconductor optical amplifier is demonstrated. A key feature of the demonstrated configuration is the ability to isolate generated sidebands from the inputs. A wave-mixing efficiency of +8.2 dB with 22.6 dB of sideband isolation at 6° separation between the two pump beams was obtained. The dependence of the efficiency on pump detuning, separation angle, and probe wavelength was also investigated. Use of a high quality traveling-wave amplifier enabled us to achieve ripple-free broadband operation over 37 nm. The demonstrated configuration is a key to practical implementations of four-wave mixing based devices. © 1997 American Institute of Physics.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.55.Px Semiconductor lasers; laser diodes
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Optical properties of tensile-strained wurtzite GaN epitaxial layers

S. Chichibu, T. Azuhata, T. Sota, H. Amano, and I. Akasaki

Appl. Phys. Lett. 70, 2085 (1997); http://dx.doi.org/10.1063/1.118958 (3 pages) | Cited 35 times

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Photo-modulated electroreflectance and photoluminescence spectra of wurtzite GaN epilayers grown on a 6H-SiC (0001)Si or a Si (111) substrate were measured as a function of temperature. The valence band structure of a biaxially tensile-strained (−0.15% in c axis) epilayer was drastically changed compared to that in unstrained and compressively strained ones; the optical transition between the conduction and the uppermost valence band exhibiting the minimum transition energy was polarized parallel to the c axis, which is characteristic of the spin split-off valence band in unstrained crystal. © 1997 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.20.Jq Electro-optical effects
78.55.Cr III-V semiconductors
71.20.Nr Semiconductor compounds

Alternating Be and C doping for strain compensated GaAs/AlAs distributed Bragg reflectors

A. Mazuelas, R. Hey, B. Jenichen, and H. T. Grahn

Appl. Phys. Lett. 70, 2088 (1997); http://dx.doi.org/10.1063/1.118952 (3 pages) | Cited 2 times

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We demonstrate a new type of strain compensated, p-type distributed Bragg reflector (DBR) using alternating doping of Be in GaAs and C in AlAs with carbon concentrations as high as 2×1020 cm−3. These DBRs exhibit simultaneously a high crystalline quality, an excellent surface morphology, and no misfit dislocations, which cannot be achieved in undoped or Be-doped DBRs. The absolute optical reflectivity is as high as in the undoped DBR. The differential resistance of these structures is comparable to best reported values in Be-doped DBRs. © 1997 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
61.72.uj III-V and II-VI semiconductors
85.40.Ry Impurity doping, diffusion and ion implantation technology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.66.Fd III-V semiconductors

Enhancement of the photonic gap of opal-based three-dimensional gratings

S. G. Romanov, N. P. Johnson, A. V. Fokin, V. Y. Butko, H. M. Yates, M. E. Pemble, and C. M. Sotomayor Torres

Appl. Phys. Lett. 70, 2091 (1997); http://dx.doi.org/10.1063/1.119081 (3 pages) | Cited 45 times

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The “semimetallic” photonic band gap formed in a synthetic opal has been increased by depositing a layer (InP or TiO2) with high refractive index on the inner surface of opal voids. Reflectance spectra of the composites (nanolayers assembled within grating voids) are correlated with both the photonic structure of the opal and electronic structure of the semiconductor. © 1997 American Institute of Physics.
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42.79.Dj Gratings
42.70.Qs Photonic bandgap materials
78.30.Hv Other nonmetallic inorganics
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Photorefractive damage removal in annealed-proton-exchanged LiNbO3 channel waveguides

Elaine E. Robertson, Robert W. Eason, Yoshiatsu Yokoo, and Peter J. Chandler

Appl. Phys. Lett. 70, 2094 (1997); http://dx.doi.org/10.1063/1.118959 (3 pages) | Cited 9 times

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Ion beam implantation has been used as a postprocessing technique to dramatically reduce the photorefractive effect in lithium niobate channel waveguides. The waveguides were fabricated by proton exchange and then annealed 1.0 MeV H+ ions were implanted through the existing channel waveguides such that the “damaged layer” was created beneath the existing channel waveguide. The output characteristics from the waveguides were subsequently examined. Highly stable single-mode outputs were observed with the waveguides retaining up to 95% of their original transmission. It is thought that this decrease in photorefractive susceptibility can be explained by the implant changing the defect structure and hence photovoltaic properties of the material. © 1997 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
78.20.-e Optical properties of bulk materials and thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.-e Ferroelectricity and antiferroelectricity
42.82.Et Waveguides, couplers, and arrays
81.40.Gh Other heat and thermomechanical treatments
61.72.up Other materials
61.80.Jh Ion radiation effects

Single-chip fused hybrids for acousto-electric and acousto-optic applications

M. Rotter, C. Rocke, S. Böhm, A. Lorke, A. Wixforth, W. Ruile, and L. Korte

Appl. Phys. Lett. 70, 2097 (1997); http://dx.doi.org/10.1063/1.118960 (3 pages) | Cited 19 times

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The combination of the electronic and optical properties of a semiconductor hetero-junction and the acoustic properties of a piezoelectric substrate material yields a new class of very promising hybrids for potential acousto-electric and acousto-optic applications. LiNbO3/GaAs hybrids have been fabricated using the epitaxial lift-off technique resulting in unusually large acousto-electric and acousto-optic interaction between the quasi two-dimensional electron system in the semiconductor and surface acoustic waves on the piezoelectric substrate. Field effect tunability of the interaction at room temperature is demonstrated and possible device applications are discussed. Photoluminescence measurements show the influence of the acousto-electric fields on the optical properties of quantum well structures. © 1997 American Institute of Physics.
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42.82.Fv Hybrid systems
42.79.Jq Acousto-optical devices
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
77.65.Dq Acoustoelectric effects and surface acoustic waves (SAW) in piezoelectrics

High velocity pseudosurface waves on LiNbO3 with thin overlayers

S. N. Makarov and A. L. Belkova

Appl. Phys. Lett. 70, 2100 (1997); http://dx.doi.org/10.1063/1.118961 (2 pages) | Cited 2 times

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A numerical study is made of high velocity pseudosurface acoustic waves (HVPSAW) on coated LiNbO3. Standard YZ and 41° YX cuts are considered. In contrast to the pure substrate, the presence of typical thin overlayers leads to the appearance of a well-localized low-attenuating HVPSAW mode at certain values of the film thickness. The depth of the localization domain may be smaller than the wavelength. © 1997 American Institute of Physics.
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43.35.Pt Surface waves in solids and liquids
68.35.Gy Mechanical properties; surface strains
77.65.Dq Acoustoelectric effects and surface acoustic waves (SAW) in piezoelectrics
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.-e Ferroelectricity and antiferroelectricity

Synthesis of fullerenes via the thermal plasma dissociation of hydrocarbons

Theodora Alexakis, Peter G. Tsantrizos, Youla S. Tsantrizos, and Jean-Luc Meunier

Appl. Phys. Lett. 70, 2102 (1997); http://dx.doi.org/10.1063/1.118962 (3 pages) | Cited 10 times

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A thermal plasma process is described for the synthesis of fullerenes via the dissociation of hydrocarbons. The plasma reactor is equipped with a nontransferred dc plasma torch which was used to dissociate hydrocarbons. The hydrocarbons investigated include CH4, C2H2, CBrF3, CCl2F2, and C2Cl4. The best results are obtained with C2Cl4. The collection temperature of the fullerene soot in the process was found to play a critical role in the collection rate of fullerenes. © 1997 American Institute of Physics.
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81.05.ub Fullerenes and related materials
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
52.75.Hn Plasma torches
81.20.-n Methods of materials synthesis and materials processing

Identification of the terminating structure of 6H–SiC(0001) by coaxial impact collision ion scattering spectroscopy

O. Ishiyama, T. Nishihara, M. Shinohara, F. Ohtani, S. Nishino, and J. Saraie

Appl. Phys. Lett. 70, 2105 (1997); http://dx.doi.org/10.1063/1.119042 (3 pages) | Cited 6 times

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The terminating structure of 6H–SiC(0001) substrates fabricated by the Acheson method was directly identified by means of coaxial impact collision ion scattering spectroscopy (CAICISS). The CAICISS spectra showed that the topmost surfaces of the samples were Si-terminated planes for both the front and rear faces. It was also shown that the (0001)Si face was composed of Si-terminated flat terraces and steps, the height of which corresponded to one-half the unit cell length along the 6H–SiC c axis. © 1997 American Institute of Physics.
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68.08.-p Liquid-solid interfaces
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
67.25.bh Films and restricted geometries
68.35.B- Structure of clean surfaces (and surface reconstruction)
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Extended x-ray absorption fine structure study of AlxGa(1−x)N films

K. E. Miyano, J. C. Woicik, Lawrence H. Robins, C. E. Bouldin, and D. K. Wickenden

Appl. Phys. Lett. 70, 2108 (1997); http://dx.doi.org/10.1063/1.118963 (3 pages) | Cited 24 times

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Extended x-ray absorption fine structure above the Ga–K edge has been used to study the local structure of AlxGa1−xN films grown by metal organic chemical vapor deposition. With increasing Al content, x, the Ga–N bond length decreases, but much less than the average bond length. On the other hand, the x dependence of the Ga–Ga and Ga–Al distances does follow the variation of the average cation–cation distance. We conclude that bond angle distortions accommodate the differences between the Ga–N and Al–N bond lengths. © 1997 American Institute of Physics.
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78.70.Dm X-ray absorption spectra
61.50.Lt Crystal binding; cohesive energy

Enhancement on field emission characteristics of pulsed laser deposited diamondlike carbon films using Au precoatings

F. Y. Chuang, C. Y. Sun, H. F. Cheng, and I. N. Lin

Appl. Phys. Lett. 70, 2111 (1997); http://dx.doi.org/10.1063/1.118964 (3 pages) | Cited 7 times

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Using Au precoatings has been observed to significantly enhance the field emission properties of diamondlike carbon (DLC) films deposited on Si substrates. The electron emission can be turned on at a low field as 7 V/μm and a large emission current density as 2000 μA/cm2 can be obtained at 20 V/μm applied field. However, preannealing the Au-coated Si substrates at 500 °C for 30 min is necessary to achieve such a performance. Microscopic examination on surface and cross-sectional morphologies of the DLC/Au/Si films using atomic force microscopy and scanning electron microscopy, respectively, in conjunction with the elemental depth profile examination of these films using secondary ion mass spectroscopy, indicated that substantial interdiffusion between DLC, Au, and Si layers has occurred. Such kind of reaction is proposed to lower the resistance for electrons to transport across the interfaces and, thereafter, enhances the field emission properties of the DLC/Au/Si films. © 1997 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
81.15.Fg Pulsed laser ablation deposition
73.61.Ng Insulators

Measurement and manipulation of Mn clusters on clean and fullerene terminated Si(111)-7×7

M. D. Upward, P. Moriarty, P. H. Beton, S. H. Baker, C. Binns, and K. Edmonds

Appl. Phys. Lett. 70, 2114 (1997); http://dx.doi.org/10.1063/1.118965 (3 pages) | Cited 16 times

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We have investigated the properties of Mn clusters deposited on clean semiconductor surfaces using an ultrahigh vacuum scanning tunnelling microscope. The clusters were formed using a gas aggregation source and were deposited on Si(111)-7×7 and Si(111)-7×7 terminated by a C60 monolayer. A distribution of cluster widths was observed with a most frequent value of 2.6 nm. There was no evidence of either cluster coalescence or preferential bonding sites. The clusters had an irregular shape, but did not appear to be grossly deformed upon adsorption onto the surface. The clusters could be selectively removed from the C60 terminated surface during scanning at negative sample bias. © 1997 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
61.46.-w Structure of nanoscale materials
82.70.-y Disperse systems; complex fluids

Smectic layer rotation by dc field in ferroelectric liquid crystal

K. Nakayama, M. Ozaki, and K. Yoshino

Appl. Phys. Lett. 70, 2117 (1997); http://dx.doi.org/10.1063/1.118966 (3 pages) | Cited 11 times

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The smectic layer rotation of a ferroelectric liquid crystal (FLC) has been investigated by applying a dc electric field. The smectic layer of FLC doped with a small amount of an ionic impurity can be rotated around the axis perpendicular to the glass plates upon application of dc voltage. This smectic layer rotation is interpreted in terms of the electrohydrodynamic flow due to an ionic impurity. © 1997 American Institute of Physics.
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61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order
77.84.Nh Liquids, emulsions, and suspensions; liquid crystals

Microstructural study of hollandite-type MnO2 nano-fibers

M. Benaissa, M. José-Yacamán, T. D. Xiao, and P. R. Strutt

Appl. Phys. Lett. 70, 2120 (1997); http://dx.doi.org/10.1063/1.119253 (3 pages) | Cited 9 times

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A new morphology of manganese oxide in the form of nano-fibers was synthesized using a novel synthetic route, and structurally characterized using high-resolution transmission electron microscopy. The obtained manganese oxide, doped with potassium, adopts a hollandite-type structure with “few useful defects” which provide an open tunneled structure in three-dimensions. This characteristic is actually believed to improve, to a high extent, the ionic conductivity of the material and exhibits the doped hollandite-type manganese oxide as a highly promising candidate for electrochemical applications such as rechargeable batteries. © 1997 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
61.72.-y Defects and impurities in crystals; microstructure

Cyclotron resonance and quantum Hall effect studies of the two-dimensional electron gas confined at the GaN/AlGaN interface

W. Knap, S. Contreras, H. Alause, C. Skierbiszewski, J. Camassel, M. Dyakonov, J. L. Robert, J. Yang, Q. Chen, M. Asif Khan, M. L. Sadowski, S. Huant, F. H. Yang, M. Goiran, J. Leotin, et al.

Appl. Phys. Lett. 70, 2123 (1997); http://dx.doi.org/10.1063/1.118967 (3 pages) | Cited 48 times

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We report on high magnetic fields (up to 40 T) cyclotron resonance, quantum Hall effect and Shubnikov-de-Hass measurements in high frequency transistors based on Si-doped GaN–AlGaN heterojunctions. A simple way of precise modelling of the cyclotron absorption in these heterojunctions is presented. We clearly establish two-dimensional electrons to be the dominant conducting carriers and determine precisely their in-plane effective mass to be 0.230±0.005 of the free electron effective mass. The increase of the effective mass with an increase of two-dimensional carrier density is observed and explained by the nonparabolicity effect. © 1997 American Institute of Physics.
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73.43.-f Quantum Hall effects
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.20.My Galvanomagnetic and other magnetotransport effects
76.40.+b Diamagnetic and cyclotron resonances
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Direct and indirect excitation of Er3+ ions in Er: AIN

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

Appl. Phys. Lett. 70, 2126 (1997); http://dx.doi.org/10.1063/1.118951 (3 pages) | Cited 37 times

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Photoluminescence (PL) excitation and time-resolved PL measurements were conducted on erbium doped AlN. The Er:AlN film was grown by metal organic molecular beam epitaxy with a solid Er effusion source. The resulting Er concentration was 2–5×1019 Er/cm3. Photoluminescence excitation measurements revealed that Er3+ in Er:AlN can be excited either through direct optical pumping into Er3+ 4f levels or through an indirect carrier-mediated process. With respect to these two Er3+ excitation schemes, distinct Er3+ PL decay patterns were observed. The Er3+ PL excited by direct optical excitation was longer lived than that excited via a carrier-mediated process. Time-resolved PL measurements support that at least two classes of Er3+ PL centers exist in Er:AlN, and that direct optical excitation of Er3+ 4f levels primarily excites a set of longer-lived Er3+ sites which are not excited through carrier-mediated processes. © 1997 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
71.20.Nr Semiconductor compounds
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Ey III-V and II-VI semiconductors
78.47.-p Spectroscopy of solid state dynamics

Nonuniform conduction in B-doped chemical vapor deposited diamond studied by intra- and intergrain measurements

S. Sahli and D. M. Aslam

Appl. Phys. Lett. 70, 2129 (1997); http://dx.doi.org/10.1063/1.118968 (3 pages) | Cited 6 times

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Current–voltage (I–V) measurements are performed on a B-doped polycrystalline diamond film chemically vapor deposited on commercially available 170-μm-thick undoped and polished polycrystalline diamond. Four-probe resistivity measurements in the temperature range of 7–200 °C, potential profile measurements across a few grains in the current range of 10−6–10−4 A, and two-probe I–V measurements within a single grain and across an individual grain boundary show that: (i) current flow is nonuniform and is affected by current level, (ii) potential barriers exist at the grain boundaries, and (iii) the probe contacts are Ohmic when the probes are placed on rough microstructures. Based on the grain size distribution, a simple model that distinguishes between conduction paths made of large grains and small grains is used to interpret these results. © 1997 American Institute of Physics.
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73.61.Cw Elemental semiconductors
61.72.Mm Grain and twin boundaries
73.40.-c Electronic transport in interface structures
73.20.At Surface states, band structure, electron density of states
68.35.B- Structure of clean surfaces (and surface reconstruction)

Cathodoluminescence and photoluminescence of highly luminescent CdSe/ZnS quantum dot composites

J. Rodriguez-Viejo, K. F. Jensen, H. Mattoussi, J. Michel, B. O. Dabbousi, and M. G. Bawendi

Appl. Phys. Lett. 70, 2132 (1997); http://dx.doi.org/10.1063/1.119043 (3 pages) | Cited 43 times

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We report room-temperature cathodoluminescence and photoluminescence spectra originating from ZnS overcoated CdSe nanocrystals, 33 and 42 Å in diameter, embedded in a ZnS matrix. The thin-film quantum dot composites were synthesized by electrospray organometallic chemical vapor deposition. Cathodoluminescence and photoluminescence are dominated by the sharp band-edge emission characteristic of the initial nanocrystals. The emission wavelength can be tuned in a broad window (470–650 nm) by varying the size of the dots. The cathodoluminescence intensity depends on the crystallinity of the ZnS matrix and the voltage and current density applied. © 1997 American Institute of Physics.
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78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
81.05.Dz II-VI semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Single-electron transistor fabricated by focused laser beam-induced doping of a GaAs/AlGaAs heterostructure

P. Baumgartner, W. Wegscheider, M. Bichler, G. Schedelbeck, R. Neumann, and G. Abstreiter

Appl. Phys. Lett. 70, 2135 (1997); http://dx.doi.org/10.1063/1.118969 (3 pages) | Cited 8 times

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A single-electron transistor has been fabricated by an optical fabrication method. A small dot, a source and drain reservoir, and in-plane gates are all built from the two-dimensional electron gas of an n-type GaAs/AlGaAs heterostructure. Laser-written p-doped lines are used to define this dot with a diameter of about 70 nm and to insulate it from the in-plane gates. Tunnel junctions connect the dot with source and drain. The in-plane gates are used to tune the tunnel junctions and to change the electrostatic potential of the dot. A large charging energy of 5 meV and clear Coulomb-blockade oscillations are observed at helium temperature, due to a small dot capacitance of about 3×10−17 F. © 1997 American Institute of Physics.
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85.35.Gv Single electron devices
85.40.Ry Impurity doping, diffusion and ion implantation technology
61.72.uj III-V and II-VI semiconductors
42.62.-b Laser applications
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Negative differential conductance at room temperature in three-terminal silicon surface junction tunneling device

Junji Koga and Akira Toriumi

Appl. Phys. Lett. 70, 2138 (1997); http://dx.doi.org/10.1063/1.118970 (3 pages) | Cited 11 times

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Negative differential conductance based on forward biased band-to-band tunneling is demonstrated at room temperature in a three-terminal silicon surface junction tunneling device. The device is fabricated on silicon dioxide to achieve an extremely small bulk leakage current together with a sharp drain impurity profile. A new device structure, in which the active tunneling junction is away from the field isolation, is also employed to totally eliminate excess tunneling current at the field oxide corner. It is observed that the tunneling current is largely controlled by the gate bias which modulates the tunneling distance. This functional device can be easily implemented into the fabrication process for silicon ultralarge scale integrated circuits, and is expected to be a useful post complementary metal–oxide–semiconductor device in future silicon technology. © 1997 American Institute of Physics.
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85.30.Tv Field effect devices
85.40.-e Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
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