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18 Oct 1999

Volume 75, Issue 16, pp. 2347-2507

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Optical and structural properties of InAs quantum dots in a GaAs matrix for a spectral range up to 1.7 μm

M. V. Maximov, A. F. Tsatsul’nikov, B. V. Volovik, D. A. Bedarev, A. Yu. Egorov, A. E. Zhukov, A. R. Kovsh, N. A. Bert, V. M. Ustinov, P. S. Kop’ev, Zh. I. Alferov, N. N. Ledentsov, D. Bimberg, I. P. Soshnikov, and P. Werner

Appl. Phys. Lett. 75, 2347 (1999); http://dx.doi.org/10.1063/1.125010 (3 pages) | Cited 35 times

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We demonstrate the possibility of extending the spectral range of luminescence due to InAs quantum dots (QDs) in a GaAs matrix up to 1.7 μm. Realization of such a long wavelength emission is related to formation of lateral associations of QDs during InAs deposition at low substrate temperatures (∼320–400 °C). © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr 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

Time-resolved soft x-ray absorption spectroscopy of silicon using femtosecond laser plasma x rays

Hidetoshi Nakano, Yoshinori Goto, Peixiang Lu, Tadashi Nishikawa, and Naoshi Uesugi

Appl. Phys. Lett. 75, 2350 (1999); http://dx.doi.org/10.1063/1.125011 (3 pages) | Cited 17 times

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We measured time-resolved soft x-ray absorption of photoexcited silicon by means of pump-probe spectroscopy, using a picosecond soft x-ray pulse from femtosecond laser-produced plasma as a probe. We observed a 5% increase in the absorption caused by 1010 W/cm2 intensity laser pulse irradiation near the LII,III edge at 100 eV. The change was observed only when the laser and the soft x-ray pulses overlapped on the sample both in time and space. © 1999 American Institute of Physics.
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78.70.Dm X-ray absorption spectra
52.70.La X-ray and γ-ray measurements
78.47.-p Spectroscopy of solid state dynamics

Red electroluminescence from ZnGaS:Mn thin films

V. Dimitrova, A. Draeseke, J. Tate, T. Yokoyama, B. L. Clark, and D. A. Keszler

Appl. Phys. Lett. 75, 2353 (1999); http://dx.doi.org/10.1063/1.125012 (3 pages) | Cited 2 times

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We demonstrate color shifting from the yellow to the red in the electroluminescence from (ZnGa)S:Mn films. We observe threshold voltages down to about 35 V, extremely low for such devices. We discuss the materials characteristics of the phosphor films, and the potential for improvement of the luminous intensity of the devices. © 1999 American Institute of Physics.
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78.60.Fi Electroluminescence
78.66.Hf II-VI semiconductors
81.05.Dz II-VI semiconductors
85.60.Jb Light-emitting devices

Parametric fluorescence in periodically poled silica fibers

G. Bonfrate, V. Pruneri, P. G. Kazansky, P. Tapster, and J. G. Rarity

Appl. Phys. Lett. 75, 2356 (1999); http://dx.doi.org/10.1063/1.125013 (3 pages) | Cited 17 times

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We report the observation of quasiphase matched parametric fluorescence from a periodically poled silica fiber. A pair-photon production rate of more than 100 MHz around 1532 nm was achieved in second-order nonlinear gratings for 300 mW of pump power at 766 nm. These results are very promising for the realization of reliable all-fiber single-photon sources for quantum cryptography systems and metrology applications. © 1999 American Institute of Physics.
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42.81.Gs Birefringence, polarization
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.55.Hx Other solid inorganic materials
42.79.Dj Gratings
42.70.Ce Glasses, quartz

Laser-induced nano-oxidation on hydrogen-passivated Ge (100) surfaces under a scanning tunneling microscope tip

Y. F. Lu, Z. H. Mai, G. Qiu, and W. K. Chim

Appl. Phys. Lett. 75, 2359 (1999); http://dx.doi.org/10.1063/1.125014 (3 pages) | Cited 35 times

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Laser-induced nano-oxidation on hydrogen-passivated Ge (100) surfaces under a scanning tunneling microscope tip in air has been investigated. A 532 nm Nd:YAG pulsed laser with a pulse duration of 7 ns was used. A 2×2 oxide dot array with dot sizes between 20 and 30 nm and an oxide single line with a width less than 30 nm have been created using an electrochemical-etched tungsten tip under laser irradiation. The modified regions were characterized by atomic force microscope. The apparent depth of oxide layer as a function of laser intensity has been studied. The advantages and drawbacks of using a continuous wave laser and a pulsed laser will be discussed. © 1999 American Institute of Physics.
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81.05.Cy Elemental semiconductors
81.65.Rv Passivation
81.65.Mq Oxidation
79.20.Ds Laser-beam impact phenomena
61.82.Fk Semiconductors

High-efficiency interband cascade lasers with peak power exceeding 4 W/facet

J. L. Bradshaw, Rui Q. Yang, J. D. Bruno, J. T. Pham, and D. E. Wortman

Appl. Phys. Lett. 75, 2362 (1999); http://dx.doi.org/10.1063/1.125015 (3 pages) | Cited 19 times

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Mid-IR (3.8–3.9 μm) interband cascade lasers based on InAs/GaInSb type-II heterostructures have been demonstrated at temperatures up to 210 K. From several lasers at temperatures above 100 K, we observed a slope greater than 750 mW/A per facet corresponding to a differential external quantum efficiency exceeding 460%. Also, a peak optical output power exceeding 4 W/facet and peak power efficiency of 7% were observed from one laser at 80 K. © 1999 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

High-power truncated-inverted-pyramid (AlxGa1−x)0.5In0.5P/GaP light-emitting diodes exhibiting >50% external quantum efficiency

M. R. Krames, M. Ochiai-Holcomb, G. E. Höfler, C. Carter-Coman, E. I. Chen, I.-H. Tan, P. Grillot, N. F. Gardner, H. C. Chui, J.-W. Huang, S. A. Stockman, F. A. Kish, M. G. Craford, T. S. Tan, C. P. Kocot, et al.

Appl. Phys. Lett. 75, 2365 (1999); http://dx.doi.org/10.1063/1.125016 (3 pages) | Cited 199 times

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A truncated-inverted-pyramid (TIP) chip geometry provides substantial improvement in light extraction efficiency over conventional AlGaInP/GaP chips of the same active junction area (∼0.25 mm2). The TIP geometry decreases the mean photon path-length within the crystal, and thus reduces the effects of internal loss mechanisms. By combining this improved device geometry with high-efficiency multiwell active layers, record-level performance for visible-spectrum light-emitting diodes is achieved. Peak efficiencies exceeding 100 lm/W are demonstrated (100 mA dc, 300 K) for orange-emitting (λp ∼ 610 nm) devices, with a peak luminous flux of 60 lumens (350 mA dc, 300 K). In the red wavelength regime (λp ∼ 650 nm), peak external quantum efficiencies of 55% and 60.9% are measured under direct current and pulsed operation, respectively (100 mA, 300 K). © 1999 American Institute of Physics.
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85.60.Jb Light-emitting devices

Measurement of internal spatial modes and local propagation properties in optical waveguides

G. H. Vander Rhodes, B. B. Goldberg, M. S. Ünlü, S. T. Chu, W. Pan, T. Kaneko, Y. Kokobun, and B. E. Little

Appl. Phys. Lett. 75, 2368 (1999); http://dx.doi.org/10.1063/1.125017 (3 pages) | Cited 18 times

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Internal spatial modes and local properties controlling optical wave propagation have been measured in glass/silica buried waveguides. The period of the observed standing modes provides a direct measure of the local effective index. The measured effective index and transverse model shape determines the values of all components of the wave vector. In addition, we describe a technique that can obtain detailed information about the locations of remote dielectric interfaces. © 1999 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
42.70.Ce Glasses, quartz
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
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Effect of growth interruptions on the interfaces of InGaAs/AlAsSb superlattice

Nikolai Georgiev and Teruo Mozume

Appl. Phys. Lett. 75, 2371 (1999); http://dx.doi.org/10.1063/1.125018 (3 pages) | Cited 6 times

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The effect of growth interruption times combined with selective group-V species exposure of InGaAs/AlAsSb short-period superlattice structure was investigated with photoluminescence, x-ray diffraction, and reflection high-energy electron diffraction. Reflection electron diffraction shows surface reconstruction transitions dependent on the time and species type exposure procedure. A shift in the photoluminescence peak position is observed from samples grown under different species type exposure compared to the samples grown without interruption, Sb termination being at a lower energy and As termination at higher energy, respectively. This is interpreted in terms of increased mixing of Sb in the interface InGaAs layers. © 1999 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.05.Ea III-V semiconductors
78.55.Cr III-V semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
78.66.Fd III-V semiconductors
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Intermixing in quantum-dot ensembles with sharp adjustable shells

S. Fafard and C. Nì. Allen

Appl. Phys. Lett. 75, 2374 (1999); http://dx.doi.org/10.1063/1.125019 (3 pages) | Cited 95 times

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State-filling spectroscopy is used to study the effects of alloy intermixing in quantum-dot (QD) ensembles having well-defined electronic shells. Rapid thermal annealing is performed on samples of self-assembled QDs grown with different intersublevel energy spacings. For InAs/GaAs QDs, the intersublevel is tuned between ∼90 and 25 meV. The intense and sharp shell structures observed in photoluminescence indicate unambiguously that the QDs retained their zero-dimensional density of states after the diffusion of the potential, which also causes strong blueshifts (up to ∼200 meV) and a pronounced narrowing of the inhomogeneously broadened emission (down to ∼12 meV). © 1999 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.05.Ea III-V semiconductors
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.72.Cc Kinetics of defect formation and annealing
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
61.82.Fk Semiconductors
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation
73.20.At Surface states, band structure, electron density of states

Coherence based contrast enhancement in x-ray radiography with a photoelectron microscope

Y. Hwu, B. Lai, D. C. Mancini, J. H. Je, D. Y. Noh, M. Bertolo, G. Tromba, and G. Margaritondo

Appl. Phys. Lett. 75, 2377 (1999); http://dx.doi.org/10.1063/1.125020 (3 pages) | Cited 5 times

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We show that a photoelectron spectromicroscope of the photoelectron emission microscope type can be used as an x-ray imaging detector for radiology. Using high penetration hard-x-ray photons (wavelength <0.1 nm), samples as thick as a few millimeters can be imaged with submicron resolution. The high imaging resolution enables us to substantially decrease the object-detector distance needed to observe coherent based contrast enhancement with respect to the standard film-based detection technique. Our result implies several advantages, the most important being a marked reduction of the required source emittance for contrast enhanced radiology. © 1999 American Institute of Physics.
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07.85.-m X- and γ-ray instruments
87.80.-y Biophysical techniques (research methods)
87.64.ks Electron and photoelectron

Damage nucleation and vacancy-induced structural transformation in Si grain boundaries

A. Maiti, S. T. Pantelides, M. F. Chisholm, and S. J. Pennycook

Appl. Phys. Lett. 75, 2380 (1999); http://dx.doi.org/10.1063/1.125021 (3 pages) | Cited 8 times

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Atomic resolution Z-contrast scanning transmission electron microscopy reveals preferential nucleation of electron-beam-induced damage in select atomic columns of a Si tilt grain boundary. Atomic scale simulations find that the region of initial damage nucleation corresponds to columns where the formation energies of vacancies and vacancy complexes are very low. The calculations further predict that vacancy accumulation in certain pairs of columns can induce a structural transformation to low-density dislocation “pipes” with all atoms fourfold coordinated. © 1999 American Institute of Physics.
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61.72.Mm Grain and twin boundaries
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
61.72.J- Point defects and defect clusters
61.80.Fe Electron and positron radiation effects
61.82.Fk Semiconductors
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

An initiation mechanism of thermal instability of a metal-diamond-vacuum field emission regime

N. S. Xu, Z. X. Yu, S. Z. Deng, J. Chen, and S. S. Wu

Appl. Phys. Lett. 75, 2383 (1999); http://dx.doi.org/10.1063/1.125121 (3 pages) | Cited 3 times

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An analysis is carried out of the physical origin of thermal instability that can trigger a catastrophic vacuum breakdown event in vacuum microelectronic devices based on flat diamond emitters. The temperature rise in a diamond film will enhance internal field emission across metal–diamond interface. This effect can lead to a regenerative process that can initiate a breakdown event at temperature lower than the melting point of an emitter. A set of equations has been developed. These theoretical findings are successfully applied to explain the instability of field emission from the nondoped diamond films. © 1999 American Institute of Physics.
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85.45.Db Field emitters and arrays, cold electron emitters
85.45.Bz Vacuum microelectronic device characterization, design, and modeling
79.70.+q Field emission, ionization, evaporation, and desorption
68.60.Dv Thermal stability; thermal effects
52.80.Vp Discharge in vacuum

Photostimulated luminescence in a rare earth-doped fluorobromozirconate glass ceramic

A. Edgar, J.-M. Spaeth, S. Schweizer, S. Assmann, P. J. Newman, and D. R. MacFarlane

Appl. Phys. Lett. 75, 2386 (1999); http://dx.doi.org/10.1063/1.125022 (3 pages) | Cited 17 times

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Photostimulated luminescence at room temperature was observed in a fluorozirconate glass which was doped with 1% Eu2+ or 1% Ce3+ and 5% Br− ions. Small crystals of BaBr2 (high-pressure phase) form in the glass on cooling. The Eu2+ and Ce3+ luminescence spectra comprised two emission lines each: for Eu2+ one line at 413 nm and a broader band centered at 485 nm, and for Ce3+ one line at 320 nm and a broader band at 425 nm. The luminescence is attributed to the 5d14fn−1→4fn emissions of the rare earth ions. In both cases only one of the emission bands showed photostimulated luminescence. The stimulation band for both rare earth ions was centered at 570 nm. © 1999 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
42.70.Ce Glasses, quartz

Violet/blue light-emitting cerium silicates

Won Chel Choi, Ho Nyung Lee, Eun Kyu Kim, Yong Kim, Chong-Yun Park, Hong Seung Kim, and Jeong Yong Lee

Appl. Phys. Lett. 75, 2389 (1999); http://dx.doi.org/10.1063/1.125023 (3 pages) | Cited 12 times

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We observed violet/blue light emitted from cerium silicates which may be useful for silicon-based optoelectronics. The cerium silicate was produced during a rapid thermal annealing at high temperature (>1100 °C) from the interface between silicon substrate and cerium oxide film. Detailed experiments including x-ray diffraction, high-resolution transmission electron microscope, and Auger depth profiling showed that the cerium silicate consists of Ce4.667(SiO4)3O and Ce2Si2O7 phases. The photoluminescence of the cerium silicate is very strong at room temperature. Specifically, the 358 nm luminescence line is attributed to the Ce2Si2O7 phase. © 1999 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation
81.40.Gh Other heat and thermomechanical treatments
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
68.35.Ct Interface structure and roughness

Crystallization kinetics and glass transition of Zr41Ti14Cu12.5Ni10−xFexBe22.5 bulk metallic glasses

Yan Xin Zhuang, Wei Hua Wang, Yong Zhang, Ming Xiang Pan, and De Qian Zhao

Appl. Phys. Lett. 75, 2392 (1999); http://dx.doi.org/10.1063/1.125024 (3 pages) | Cited 49 times

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The crystallization kinetics and glass transition behavior of Zr41Ti14Cu12.5Ni10−xFexBe22.5 (x = 0, 2, and 5) bulk metallic glasses (BMGs) have been investigated by means of differential scanning calorimeter under nonisothermal conditions. The glass transition temperature Tg, the onset crystallization temperature Tx, and the crystallization peak temperature Tpi of the BMGs are found to depend on the heating rate during the continuous heating. The effective activation energy and the frequency factor of the glass transition and crystallization of the BMGs are determined by the Kissinger method. The glass forming ability of the glass forming alloys has been discussed in view of the crystallization kinetics. © 1999 American Institute of Physics.
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61.43.Fs Glasses
64.70.D- Solid-liquid transitions
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition

Strain relaxation of faceted Ge islands on Si(113)

Jian-hong Zhu, C. Miesner, K. Brunner, and G. Abstreiter

Appl. Phys. Lett. 75, 2395 (1999); http://dx.doi.org/10.1063/1.125025 (3 pages) | Cited 20 times

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We studied the formation and strain relaxation of Ge islands on Si(113) grown at 700 °C by molecular beam epitaxy. Atomic force microscopy reveals that they are mainly (113) top faceted and show a mesa-like shape. Initially formed Ge islands tend to elongate along [33math] due to their anisotropic shear strain. With increasing Ge coverage, they grow mainly laterally towards particular directions, forming large V-shaped Ge clusters. This is analyzed to be caused by the formation of {111} slide plane-associated dislocations. The dislocations are shown to be localized in the islands. Considerable Si material has diffused into the Ge islands. Strain and Ge content in the islands are quantitatively analyzed by micro-Raman spectroscopy. © 1999 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.30.Am Elemental semiconductors and insulators
78.66.Db Elemental semiconductors and insulators
81.05.Cy Elemental semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.Nq Composition and phase identification
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation
68.35.Gy Mechanical properties; surface strains
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)

A two-component phosphor approach for engineering electroluminescence phosphors

T. C. Jones, W. Park, and C. J. Summers

Appl. Phys. Lett. 75, 2398 (1999); http://dx.doi.org/10.1063/1.125026 (3 pages) | Cited 3 times

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The electroluminescence (EL) properties of SrS:Cu, SrS:Ag, and SrS:Ag,Cu thin-film phosphors are reported. SrS:Cu and SrS:Ag are shown to exhibit very different EL properties with SrS:Cu possessing a luminance and efficiency of 30.8 cd/m2 and 0.2 lm/W, compared to SrS:Ag whose luminance and efficiency are 0.7 cd/m2 and 0.001 lm/W, respectively. In contrast, SrS:Ag,Cu exhibits the high luminance and efficiency of SrS:Cu, but the saturated chromaticity of SrS:Ag, which exhibits an excellent blue chromaticity of (0.17,0.15). The improved electroluminescent luminance, efficiency, and color purity of SrS:Ag,Cu are explained by the energy transfer from the Cu+ to Ag+ ions. These results suggest a concept to improve EL performance through the use of a class of two-component phosphors, which exhibit superior color, brightness, and excitation efficiency. © 1999 American Institute of Physics.
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78.60.Fi Electroluminescence
78.66.Nk Insulators
85.60.Pg Display systems

Electron-induced crosslinking of aromatic self-assembled monolayers: Negative resists for nanolithography

W. Geyer, V. Stadler, W. Eck, M. Zharnikov, A. Gölzhäuser, and M. Grunze

Appl. Phys. Lett. 75, 2401 (1999); http://dx.doi.org/10.1063/1.125027 (3 pages) | Cited 92 times

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We have explored the interaction of self-assembled monolayers of 1,1′-biphenyl-4-thiol (BPT) with low energy electrons. X-ray photoelectron, infrared, and near edge x-ray absorption fine structure spectroscopy showed that BPT forms well-ordered monolayers with the phenyl rings tilted ∼15° from the surface normal. The films were exposed to 50 eV electrons and changes were monitored in situ. Even after high (∼10 mC/cm2) exposures, the molecules maintain their preferred orientation and remain bonded on the gold substrate. An increased etching resistance and changes in the infrared spectra imply a crosslinking between neighboring phenyl groups, which suggests that BPT can be utilized as an ultrathin negative resist. This is demonstrated by the generation of patterns in the underlying gold. © 1999 American Institute of Physics.
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68.18.-g Langmuir-Blodgett films on liquids
61.80.Fe Electron and positron radiation effects
61.82.Pv Polymers, organic compounds
85.40.Hp Lithography, masks and pattern transfer
68.55.-a Thin film structure and morphology
79.60.Fr Polymers; organic compounds
79.60.Dp Adsorbed layers and thin films
78.30.Jw Organic compounds, polymers
78.66.Qn Polymers; organic compounds
78.70.Dm X-ray absorption spectra
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Characterization of silicon-silicon bonds on the Si(100) surfaces

Dominic R. Alfonso

Appl. Phys. Lett. 75, 2404 (1999); http://dx.doi.org/10.1063/1.125028 (3 pages) | Cited 1 time

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The bonding nature of the surface atoms in the (2×1) and c(4×2) reconstruction of the Si(100) surface has been characterized using local analysis technique in the context of nonorthogonal tight binding approximation. We demonstrate the capability of this method to yield a real-space picture of the bonding character of the surface atoms for these systems. We also report our analysis of the surface atom bonds on the Si(100) substrate with single-dimer vacancy. © 1999 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
81.05.Cy Elemental semiconductors
61.50.Lt Crystal binding; cohesive energy
68.35.Rh Phase transitions and critical phenomena
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)

Polarization fields determination in AlGaN/GaN heterostructure field-effect transistors from charge control analysis

J. A. Garrido, J. L. Sánchez-Rojas, A. Jiménez, E. Muñoz, F. Omnes, and P. Gibart

Appl. Phys. Lett. 75, 2407 (1999); http://dx.doi.org/10.1063/1.125029 (3 pages) | Cited 32 times

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AlxGa1−xN/GaN heterostructure field-effect transistors with different Al concentrations (0.15<x<0.25) and barrier widths (150 Å<WB<350 Å) have been fabricated and characterized. Experimental results were analyzed by using a self-consistent solution of the Schrödinger and Poisson equations with the proper boundary conditions. The total (piezoelectric and spontaneous) polarization has been included as a fitting parameter in the self-consistent calculations. From the analysis of the transistor charge-control experimental data, a linear increase of the polarization field with the Al concentration has been found. Our results indicate that the slope of such dependence, and the magnitude of the total polarization field are lower than the predicted ones using the usually accepted values of the piezoelectric and spontaneous polarization coefficients. © 1999 American Institute of Physics.
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85.30.Tv Field effect devices
77.65.-j Piezoelectricity and electromechanical effects
85.30.De Semiconductor-device characterization, design, and modeling
02.30.Jr Partial differential equations
02.60.Lj Ordinary and partial differential equations; boundary value problems

On field emission from a semiconducting substrate

Richard Waters and Bart Van Zeghbroeck

Appl. Phys. Lett. 75, 2410 (1999); http://dx.doi.org/10.1063/1.125030 (3 pages) | Cited 8 times

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A theoretical examination of field emission from the conduction band of a semiconducting substrate is reported. The analysis includes a comparison with Fowler–Nordheim theory, and it is concluded that the formalism of the Fowler–Nordheim theory is incorrect when applied to carriers originating from a semiconducting substrate. The use of a Fowler–Nordheim analysis results in an error in the extraction of the barrier height that is dependent upon the applied electric field across the oxide, conduction band offset, and temperature. A lower limit of the error was calculated to be between 5% and 15%. An analytical expression is developed to describe the field emission of electrons from the conduction band of a semiconductor. © 1999 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
73.20.At Surface states, band structure, electron density of states

Infrared and photoluminescence spectroscopy of p-doped self-assembled Ge dots on Si

L. P. Rokhinson, D. C. Tsui, J. L. Benton, and Y.-H. Xie

Appl. Phys. Lett. 75, 2413 (1999); http://dx.doi.org/10.1063/1.125031 (3 pages) | Cited 15 times

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We report infrared photocurrent (PC) and photoluminescence (PL) spectroscopy of self-assembled Ge dots grown on Si(100) by molecular beam epitaxy. PL spectra show a transition from two- to three-dimensional growth as the Ge thickness exceeds 7 Å. The sum of the PC peak energy and PL energy from Ge dots is found to be approximately equal to the energy band gap of Si. Boron doping changes the energy spectrum of the dots: PL peaks from both doped Ge dots and from the wetting layer are shifted to higher energy, compared to the undoped samples. Also, the TO phonon energy from the wetting layer is reduced to 38 meV. © 1999 American Institute of Physics.
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78.66.Db Elemental semiconductors and insulators
73.61.Cw Elemental semiconductors
78.55.Ap Elemental semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.30.Am Elemental semiconductors and insulators
72.40.+w Photoconduction and photovoltaic effects
73.50.Pz Photoconduction and photovoltaic effects
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
63.20.-e Phonons in crystal lattices

Studies of metal–ferroelectric–GaN structures

W. P. Li, R. Zhang, Y. G. Zhou, J. Yin, H. M. Bu, Z. Y. Luo, B. Shen, Y. Shi, R. L. Jiang, S. L. Gu, Z. G. Liu, Y. D. Zheng, and Z. C. Huang

Appl. Phys. Lett. 75, 2416 (1999); http://dx.doi.org/10.1063/1.125032 (2 pages) | Cited 24 times

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A GaN-based metal–insulator–semiconductor (MIS) structure has been fabricated by using ferroelectric Pb(Zr0.53Ti0.47)O3 instead of conventional oxides as insulator gate. Because of the polarization field provided by ferroelectric and the high dielectric constant of ferroelectric insulator, the capacitance–voltage characteristics of GaN-based metal–ferroelectric–semiconductor (MFS) structures are markedly improved compared to those of other previously studied GaN MIS structures. The GaN active layer in MFS structures can reach inversion just under the bias of smaller than 5 V, which is the generally applied voltage used in semiconductor-based integrated circuits. The surface carrier concentration of the GaN layer in the MFS structure is decreased by one order compared with the background carrier concentration. The GaN MFS structures look promising for the practical application of GaN-based field effect transistors. © 1999 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ej Polarization and depolarization
85.30.Tv Field effect devices

Theory of the charge-transport properties of naphthyl diamine used in organic light-emitting devices

R. Q. Zhang, C. S. Lee, and S. T. Lee

Appl. Phys. Lett. 75, 2418 (1999); http://dx.doi.org/10.1063/1.125033 (3 pages) | Cited 10 times

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The electronic structures of a prototypical electroluminescent molecule, N,N′-bis-(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB), with various extra charges (+6 to −6 atomic units), have been theoretically studied by means of the PM3 and ab initio molecular orbital theories as well as density functional theory in combination with a decomposition of the density of states. It was found that, under positive charging, the essential distribution feature of the molecular orbitals at constituent atoms in the NPB molecule can still favor carrier transport, but cannot do so under negative charging. By explaining the efficient hole-transporting property of NPB, the present study elucidates the potential of the theoretical approach for the selection of optimum carrier-transporting organic materials. © 1999 American Institute of Physics.  
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85.60.Jb Light-emitting devices
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.20.Rv Polymers and organic compounds
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