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31 Aug 1998

Volume 73, Issue 9, pp. 1167-1303

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Optical limiting performances of asymmetric pentaazadentate porphyrin-like cadmium complexes

Wenfang Sun, Clare C. Byeon, Michael M. McKerns, Chris M. Lawson, Gary M. Gray, and Duoyuan Wang

Appl. Phys. Lett. 73, 1167 (1998); http://dx.doi.org/10.1063/1.122366 (3 pages) | Cited 24 times

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The optical limiting performances of seven asymmetric pentaazadentate porphyrin-like cadmium complexes have been measured at 532 nm with nanosecond pulses. In a f/38 geometry, with sample transmission of 0.51–0.80 in a 2 mm cell, the limiting thresholds for these complexes were 1.4–3.0 mJ/cm2.The throughputs of these complexes were limited to 0.31–1.13 J/cm2 for incident fluences as high as 3.5 J/cm2. The limiting throughput was strongly influenced by the nature of the ligand. Lower bounds for the ratio of triplet excited-state to ground-state absorption cross sections have been estimated at 3.4–5.7. The lower limiting thresholds, lower limiting throughputs, as well as the ease of modification of the ligands, make these complexes promising candidates for optical power limiters. © 1998 American Institute of Physics.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
78.47.-p Spectroscopy of solid state dynamics
78.40.-q Absorption and reflection spectra: visible and ultraviolet
78.30.-j Infrared and Raman spectra

Computer simulations on near-field scanning optical microscopy: Can subwavelength resolution be obtained using uncoated optical fiber probes?

G. von Freymann, Th. Schimmel, M. Wegener, B. Hanewinkel, A. Knorr, and S. W. Koch

Appl. Phys. Lett. 73, 1170 (1998); http://dx.doi.org/10.1063/1.122118 (3 pages) | Cited 13 times

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Recent experiments claim that subwavelength resolution can be obtained with an optical scanning microscope using uncoated optical fiber probes. In these experiments, linearly polarized light is sent down the fiber which is reflected and depolarized in the tip-sample region. The internally reflected signal in the orthogonal polarization is detected. Here, numerical solutions of the vector Maxwell equations for a model are discussed. In this model, subwavelength resolution can indeed be obtained in the above mode, while this is not possible without polarization sensitivity. The influence of parameters such as polarization, different scanning modes and tip-sample distance is discussed. © 1998 American Institute of Physics.
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07.79.Fc Near-field scanning optical microscopes

Frequency dependence of radar cross section for arbitrarily shaped scatterers

Hongwei Liu, Yahia M. M. Antar, Zhendong Shi, and Zhengde Wu

Appl. Phys. Lett. 73, 1173 (1998); http://dx.doi.org/10.1063/1.122119 (3 pages)

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This letter introduces a method to perform frequency dependence of radar cross section for either simple or complex scatters in terms of model measurement. To do so, the expressions of physical scale factor based on the electromagnetic similarity are suggested by means of dimensional analysis, geometric and physical optics approximation. Using the results of model measurement within a small range of frequency, the frequency dependence of an arbitrarily shaped scatterer can be obtained. For the purpose of verification and comparison, some measurements of simple and complex shapes have been carried out. The calculated results agree well with the experimental data on the prototype itself. © 1998 American Institute of Physics.
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41.20.Jb Electromagnetic wave propagation; radiowave propagation
84.40.Xb Telemetry: remote control, remote sensing; radar

Cobalt nanoclusters in silica glass: Nonlinear optical and magnetic properties

E. Cattaruzza, F. Gonella, G. Mattei, P. Mazzoldi, D. Gatteschi, C. Sangregorio, M. Falconieri, G. Salvetti, and G. Battaglin

Appl. Phys. Lett. 73, 1176 (1998); http://dx.doi.org/10.1063/1.122120 (3 pages) | Cited 31 times

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Fused silica plates were implanted with Co ions at room temperature at the energy of 50 keV and to the fluence of 4×1016 ions cm−2. The formation of metal nanoclusters was observed by transmission electron microscopy. The cluster size distribution is narrow with a mean-diameter value of about 3 nm. Atomic in-depth distribution was determined by Rutherford backscattering spectrometry, whereas the cobalt chemical state was characterized by electron spectroscopies. Nonlinear refractive index n2 is of the order of 0.2 cm2 G W−1, as determined by the Z-scan technique at a wavelength of 770 nm for 130 fs long pulses at a 76 MHz repetition rate. Zero-field-cooled and field-cooled magnetization curves at the liquid-helium temperature exhibit features of superparamagnetic behavior that are characteristic of assemblies of single-domain nanoparticles. © 1998 American Institute of Physics.
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75.50.Kj Amorphous and quasicrystalline magnetic materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
75.50.Tt Fine-particle systems; nanocrystalline materials
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
61.46.-w Structure of nanoscale materials
61.80.Jh Ion radiation effects
61.72.up Other materials
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
79.60.Jv Interfaces; heterostructures; nanostructures
79.20.Fv Electron impact: Auger emission
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
42.65.-k Nonlinear optics

GaN epitaxial lateral overgrowth and optical characterization

X. Li, S. G. Bishop, and J. J. Coleman

Appl. Phys. Lett. 73, 1179 (1998); http://dx.doi.org/10.1063/1.122121 (3 pages) | Cited 20 times

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We demonstrate the epitaxial lateral overgrowth (ELO) of GaN from narrow stripes with triangular cross sections by atmospheric pressure metal organic chemical vapor deposition, and characterize the optical properties of these stripes at each stage of the growth using spatially resolved cathodoluminescence spectroscopy, wavelength imaging, and line scans. An improvement of the optical quality of the GaN materials grown by the ELO technique is clearly shown by the appearance of a free exciton peak, the enhancement of bandedge emission, and the weakening of the yellow emission. © 1998 American Institute of Physics.
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81.05.Ea III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.66.Fd III-V semiconductors
71.35.-y Excitons and related phenomena
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

High-power (>10 W) continuous-wave operation from 100-μm-aperture 0.97-μm-emitting Al-free diode lasers

A. Al-Muhanna, L. J. Mawst, D. Botez, D. Z. Garbuzov, R. U. Martinelli, and J. C. Connolly

Appl. Phys. Lett. 73, 1182 (1998); http://dx.doi.org/10.1063/1.122122 (3 pages) | Cited 62 times

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By incorporating a broad transverse waveguide (1.3 μm) in 0.97-μm-emitting InGaAs(P)/InGaP/GaAs separate-confinement-heterostructure quantum-well diode-laser structures we obtain record-high continuous-wave (cw) output powers for any type of InGaAs-active diode lasers: 10.6–11.0 W from 100-μm-wide-aperture devices at 10 °C heatsink temperature, mounted on either diamond or Cu heatsinks. Built-in discrimination against the second-order transverse mode allows pure fundamental-transverse-mode operation (θ⊥ = 36°) to at least 20-W-peak pulsed power, at 68×threshold. The internal optical power density at catastrophic optical mirror damage (COMD) mathCOMD is found to be 18–18.5 MW/cm2 for these conventionally facet-passivated diodes. The lasers are 2-mm-long with 5%/95% reflectivity for front/back facet coating. A low internal loss coefficient (αi = 1 cm−1) allows for high external differential quantum efficiency ηd (85%). The characteristic temperatures for the threshold current T0 and the differential quantum efficiency T1 are 210 and 1800 K, respectively. Low differential series resistance Rs: 26 mΩ; leads to electrical-to-optical power conversion efficiency values in excess of 40% from 1 W up to 10.6 W cw output power, and as much as 50% higher than those of 0.97-μm-emitting Al-containing devices. © 1998 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Aluminum based cathode structure for enhanced electron injection in electroluminescent organic devices

G. E. Jabbour, B. Kippelen, N. R. Armstrong, and N. Peyghambarian

Appl. Phys. Lett. 73, 1185 (1998); http://dx.doi.org/10.1063/1.122367 (3 pages) | Cited 145 times

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Cathodes made with Al–LiF or Al–CsF composites are found to greatly enhance the performance of organic light-emitting devices (OLEDs). With a composite cathode, devices based on an organic bilayer structure have shown lower operating voltage, higher efficiency, and better forward light output than devices with LiF/Al, Mg, or Al cathode. Unlike devices with an Al and Li alloy cathode, OLEDs with a composite cathode can be made with good reproducibility. © 1998 American Institute of Physics.
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85.60.Jb Light-emitting devices
82.45.-h Electrochemistry and electrophoresis

Optical spectroscopy of Si-related donor and acceptor levels in Si-doped GaN grown by hydride vapor phase epitaxy

J. Jayapalan, B. J. Skromme, R. P. Vaudo, and V. M. Phanse

Appl. Phys. Lett. 73, 1188 (1998); http://dx.doi.org/10.1063/1.122123 (3 pages) | Cited 41 times

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The optical properties of n-type GaN grown by hydride vapor phase epitaxy, with intentional Si doping levels ranging from nominally undoped to ND−NA = 4×1017 cm−3, are investigated using low temperature photoluminescence. We identify free and neutral donor-bound exciton transitions and two-electron satellites (TES) at 1.7 K. The energy difference between the principal neutral donor-bound exciton peak and its TES yields a Si donor binding energy of 22 meV. The intensity of the Si-related TES increases with increasing Si concentration. The Si donor is much shallower than the two residual donors, which have binding energies of 28 and 34 meV. This result suggests that the main residual donors in this material (and possibly in many layers grown by metal organic chemical vapor deposition and metal organic molecular beam epitaxy as well) are not Si. Silicon doping also introduces an acceptor level with a binding energy of about 224 meV. © 1998 American Institute of Physics.
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78.66.Fd III-V semiconductors
71.55.Eq III-V semiconductors
78.55.Cr III-V semiconductors
71.35.-y Excitons and related phenomena

Antireflection coatings for PbSe diode lasers

T. Beyer and M. Tacke

Appl. Phys. Lett. 73, 1191 (1998); http://dx.doi.org/10.1063/1.122368 (3 pages) | Cited 7 times

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The antireflection coating of PbSe laser diodes is crucial for external resonator lasers. In situ determination of the threshold current in cryogenic temperature operation is used in order to optimize the thickness of evaporated layers for minimum reflection. © 1998 American Institute of Physics.
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42.79.Wc Optical coatings
42.55.Px Semiconductor lasers; laser diodes
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
68.55.-a Thin film structure and morphology
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Raman study of BaFe12O19 thin films

J. Kreisel, S. Pignard, H. Vincent, J. P. Sénateur, and G. Lucazeau

Appl. Phys. Lett. 73, 1194 (1998); http://dx.doi.org/10.1063/1.122124 (3 pages) | Cited 17 times

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We report on Raman spectra of BaFe12O19 thin films. These thin films have been deposited by injection chemical vapor deposition on three different substrates: Al2O3 (001), Gd3Ga5O12 (111), and Si (100). The observed Raman-active vibrations of the films are compared with recently published Raman spectra from bulk compounds. Surprisingly, we observed nearly the same spectra for all the films, although x-ray diffraction indicates polycrystalline (Si), textured (Gd3Ga5O12), and epitaxial (Al2O3) structure. We interpret these results by supposing the coexistence of well oriented regions and randomly oriented microcrystallites, which are not detectable by x-ray diffraction. Furthermore, by Raman spectroscopy we identified an additional phase for the films deposited on Al2O3 which has not been observed by x-ray diffraction either. © 1998 American Institute of Physics.
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78.30.Hv Other nonmetallic inorganics
63.20.-e Phonons in crystal lattices
78.66.-w Optical properties of specific thin films
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Alignment of carbon nanotubes in a polymer matrix by mechanical stretching

L. Jin, C. Bower, and O. Zhou

Appl. Phys. Lett. 73, 1197 (1998); http://dx.doi.org/10.1063/1.122125 (3 pages) | Cited 223 times

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We report a method to fabricate polymer-based composites with aligned carbon nanotubes, and a procedure to determine the nanotube orientation and the degree of alignment. The composites were fabricated by casting a suspension of carbon nanotubes in a solution of a thermoplastic polymer and chloroform. They were uniaxially stretched at 100 °C and were found to remain elongated after removal of the load at room temperature. The orientation and the degree of alignment were determined by x-ray diffraction. The dispersion and the alignment of the nanotubes were also studied by transmission electron microscopy. © 1998 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

Lattice deformation and magnetic properties in epitaxial thin films of Sr1−xBaxRuO3

Noburu Fukushima, Kenya Sano, Tatsuo Schimizu, Kazuhide Abe, and Shuichi Komatsu

Appl. Phys. Lett. 73, 1200 (1998); http://dx.doi.org/10.1063/1.122126 (3 pages) | Cited 9 times

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Crystal structure and magnetic properties in epitaxially grown Sr1−xBaxRuO3 on SrTiO3 substrates were determined. Epitaxial Sr1−xBaxRuO3 exhibits a simple perovskite structure in the whole region of the Ba/Sr ratio, in contrast to the complex hexagonal layered perovskite of Ba-rich bulk Sr1−xBaxRuO3, which has plane-sharing oxygen octahedra. Tetragonal deformation was enhanced from pseudocubic in SrRuO3 to a highly distorted tetragonal lattice in BaRuO3. Electronic properties such as conductivity and magnetization were examined. A metal–insulator transition was not observed in this system, and metallic conductivity was maintained in the whole region of Ba concentration. Ferromagnetic ordering at 160 K seen in bulk SrRuO3 was observed to be suppressed in the Sr1−xBaxRuO3 films with increasing tetragonal deformation and Curie temperatures decreased to 50 K in BaRuO3. © 1998 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
68.55.-a Thin film structure and morphology
71.27.+a Strongly correlated electron systems; heavy fermions
73.61.-r Electrical properties of specific thin films

Micro-Raman fingerprint of grain boundary in [100] oriented diamond films: Stress distribution and diamond phases

Maria Cristina Rossi

Appl. Phys. Lett. 73, 1203 (1998); http://dx.doi.org/10.1063/1.122127 (3 pages) | Cited 8 times

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Local distribution of stress state and carbon bonding in diamond films are studied by micro-Raman spectroscopy. Large changes in intensity, line shape, and peak position of the diamond Raman line occur close to the grain boundary. The characteristic feature of such region is a 1326 cm−1 Raman peak, whose detection suggests that defect incorporation at the grain boundary may promote a diamond symmetry modification from a cubic to hexagonal one. Close to intergrain locations, large anisotropic stresses also induce frequency splitting of the Raman line. Suitable stress configurations consistent with the detection of an almost unshifted component and of a largely frequency-changing mode are analyzed. © 1998 American Institute of Physics.  
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81.05.ub Fullerenes and related materials
68.60.Bs Mechanical and acoustical properties
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
78.66.Db Elemental semiconductors and insulators
61.72.Mm Grain and twin boundaries
78.30.Am Elemental semiconductors and insulators

Diffusion of iron in the silicon dioxide layer of silicon-on-insulator structures

O. Kononchuk, K. G. Korablev, N. Yarykin, and G. A. Rozgonyi

Appl. Phys. Lett. 73, 1206 (1998); http://dx.doi.org/10.1063/1.122128 (3 pages) | Cited 13 times

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The redistribution of iron implanted into the oxide layer of silicon-on-insulator structures has been measured using the secondary ion mass spectroscopy technique after annealing at 900–1050 °C. Iron diffusion has been found to be much faster in the oxide prepared by the separation-byimplantation-of-oxygen (SIMOX) procedure compared to the thermally grown oxide in the bonded and etched-back structures. In the latter case, the Fe diffusivity exhibits a thermal activation with an energy of 2.8 eV, confirming the literature data on silica glass. In the SIMOX oxide, the diffusivity depends only weakly on temperature, indicative of an essentially activation-free diffusion mechanism. Gettering of Fe at below-the-buried-oxide defects in SIMOX wafers has been observed. No iron segregation has been detected at the SiO2–Si interfaces. © 1998 American Institute of Physics.
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66.30.J- Diffusion of impurities
61.72.Cc Kinetics of defect formation and annealing
61.72.S- Impurities in crystals
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Structural relaxation enhanced by Cl ions in silica glass

K. Saito and A. J. Ikushima

Appl. Phys. Lett. 73, 1209 (1998); http://dx.doi.org/10.1063/1.122129 (3 pages) | Cited 14 times

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The effect of Cl ions on the structural relaxation in silica glass was investigated by observing the fictive temperature, which was determined from the position of infrared absorption peak around 2260 cm−1 related to the average Si–O–Si bond angle. It has been found that Cl ions reduce the relaxation time of the long-range cooperative relaxation due to viscous flow, the so-called α relaxation. Moreover, Cl ions reduce the relaxation time of a subrelaxational process, caused by local structural relaxation. Although Cl has been used in industry only for dehydrating silica glass for optical fibers, these structural relaxation enhanced by Cl may be used advantageously to develop ultralow-loss fiber glass. © 1998 American Institute of Physics.
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61.43.Fs Glasses
81.05.Kf Glasses (including metallic glasses)
78.35.+c Brillouin and Rayleigh scattering; other light scattering

Raman study of silicon nanocrystals formed in SiNx films by excimer laser or thermal annealing

V. A. Volodin, M. D. Efremov, V. A. Gritsenko, and S. A. Kochubei

Appl. Phys. Lett. 73, 1212 (1998); http://dx.doi.org/10.1063/1.122130 (3 pages) | Cited 25 times

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Silicon nitride films of different stoichiometric composition were studied using Raman spectroscopy. A Raman signal due to Si–Si, Si–N bond vibrations in silicon nanoclusters was detected in as-deposited films. The appearance of Raman peaks in the range 493–514 cm−1 after thermal and pulse laser treatments was interpreted as formation of silicon nanocrystals with sizes from 1.3 up to 5 nm depending on treatment parameters. Thermal treatment at 1200 °C allowed Si atom diffusion and its gathering in Si nanocrystals, meanwhile 5 ns pulse laser irradiation leads to crystallization of preexisting silicon nanoclusters inside the as-deposited SiNx films. © 1998 American Institute of Physics.
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61.72.Cc Kinetics of defect formation and annealing
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
78.30.Hv Other nonmetallic inorganics
61.46.-w Structure of nanoscale materials
78.30.Am Elemental semiconductors and insulators
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
66.30.H- Self-diffusion and ionic conduction in nonmetals
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Franz–Keldysh oscillations from combined space-charge and grading fields as observed in graded emitter GaAlAs/GaAs heterojunction bipolar transistor structures

Y. S. Huang, W. D. Sun, L. Malikova, Fred H. Pollak, T. S. Low, and James S. C. Chang

Appl. Phys. Lett. 73, 1215 (1998); http://dx.doi.org/10.1063/1.122131 (3 pages) | Cited 9 times

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We have performed a systematic room-temperature photoreflectance study of Franz–Keldysh oscillations from the Ga0.77Al0.23As emitter and GaAs collector regions of a series of graded band-gap emitter GaAlAs/GaAs heterojunction bipolar transistor structures in which both the emitter grading and doping [space-charge field (SCF)] have been varied. It is found that the fields in the emitter depend on both the grading field and SCF, in agreement with the recent theory of Sun and Pollak [W. P. Sun and F. H. Pollak, J. Appl. Phys. 83, 4447 (1998)]. Good agreement for both the collector and emitter fields is found between experiment and simulation using a comprehensive, self-consistent model, including the photovoltaic effect. © 1998 American Institute of Physics.
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85.30.Pq Bipolar transistors
78.20.-e Optical properties of bulk materials and thin films
78.66.Fd III-V semiconductors
73.50.Pz Photoconduction and photovoltaic effects
73.61.Ey III-V semiconductors

A highly transmittive semiconductor base for ballistic electron emission microscopy

R. Heer, J. Smoliner, G. Strasser, and E. Gornik

Appl. Phys. Lett. 73, 1218 (1998); http://dx.doi.org/10.1063/1.122132 (3 pages) | Cited 12 times

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Ballistic electron emission spectroscopy and ballistic electron emission microscopy offer the unique possibility of probing subsurface quantum states. To improve the spectroscopic sensitivity, it is important to increase the amount of electrons, which are able to penetrate into the sample. In this work, we show that the transmission coefficient and the attenuation length of the base layer can be enhanced by more than one order of magnitude, if the commonly used thin metal film is replaced by a molecular beam epitaxy grown InAs layer. At low temperatures (T = 100 K), a passivated InAs layer yields an attenuation length in the order of 70–90 nm instead of 5 nm obtained on Au films. © 1998 American Institute of Physics.
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68.37.Vj Field emission and field-ion microscopy
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.20.At Surface states, band structure, electron density of states

Quantum interference in SiO2: A conduction-band mass reappraisal

R. Ludeke, H. J. Wen, and Andreas Schenk

Appl. Phys. Lett. 73, 1221 (1998); http://dx.doi.org/10.1063/1.122133 (3 pages) | Cited 4 times

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Quantum oscillations arising from interference in over-the-barrier injected electrons crossing a metal–oxide–semiconductor structure were observed for a 2.8 nm SiO2 layer. Model calculations that include image force effects are fitted to the data to obtain a conduction-band mass of mox = (0.63±0.09)m0. The field dependence of the oscillations was used to deduce the polarity and magnitudes of oxide charge induced by the high fluence of electrons injected with the scanning tunneling microscope during spectral acquisitions. © 1998 American Institute of Physics.
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73.23.-b Electronic transport in mesoscopic systems
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
73.61.Ng Insulators

Minority-carrier lifetime and efficiency of Cu(In,Ga)Se2 solar cells

B. Ohnesorge, R. Weigand, G. Bacher, A. Forchel, W. Riedl, and F. H. Karg

Appl. Phys. Lett. 73, 1224 (1998); http://dx.doi.org/10.1063/1.122134 (3 pages) | Cited 21 times

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Room-temperature recombination dynamics has been investigated in a large set of different Cu(In,Ga)Se2 absorber films and compared to the electrical device characteristics of the respective solar cell modules. For a given cell preparation process, a characteristic relation between the low-injection minority-carrier lifetime of the absorber layers and the conversion efficiency of the solar cells is observed: Long lifetimes correlate with high open circuit voltages and conversion efficiencies, while no significant influence of the lifetime on the short circuit current is found. © 1998 American Institute of Physics.
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84.60.Jt Photoelectric conversion
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.61.Le Other inorganic semiconductors

Impact ionization in AlxGa1−xAs/GaAs superlattices

T. P. Pearsall

Appl. Phys. Lett. 73, 1227 (1998); http://dx.doi.org/10.1063/1.122135 (3 pages) | Cited 3 times

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The role of band discontinuities on electron ionization rates is examined for the case of GaAs/AlGaAs superlattice avalanche photodiode structures. Our results show that the energy discontinuity experienced by a hot electron (E>0.4 eV above the Fermi level) is small or even negative relative to the conduction-band energy discontinuity experienced by an electron at the band edge of the Γ valley in GaAs/AlGaAs heterostructures. This finding does not support the measurement of an enhanced electron ionization rate due to transport through a superlattice composed of this materials system. © 1998 American Institute of Physics.  
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73.61.Ey III-V semiconductors
73.50.Fq High-field and nonlinear effects
85.60.Dw Photodiodes; phototransistors; photoresistors

Green photoluminescence from cubic In0.4Ga0.6N grown by radio frequency plasma-assisted molecular beam epitaxy

J. R. Müllhäuser, O. Brandt, A. Trampert, B. Jenichen, and K. H. Ploog

Appl. Phys. Lett. 73, 1230 (1998); http://dx.doi.org/10.1063/1.122136 (3 pages) | Cited 13 times

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We investigate the structural and optical properties of a cubic (In, Ga)N/GaN/(Al, Ga)N heterostructure containing a 185 nm thick In0.4Ga0.6N layer which dominates the optical properties of the sample. The phase purity of the structure is verified by means of transmission electron microscopy while the In content is measured by x-ray diffraction and secondary ion mass spectrometry. The room-temperature band gap of the In0.4Ga0.6N layer is determined by transmission and reflectance measurements to be 2.46±0.03 eV. This value agrees with the spectral position of the dominating green photoluminescence at 300 K. © 1998 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
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
71.20.Nr Semiconductor compounds

Microstructural evolution of GaSb self-assembled islands grown by metalorganic chemical vapor deposition

B. M. Kinder and E. M. Goldys

Appl. Phys. Lett. 73, 1233 (1998); http://dx.doi.org/10.1063/1.122137 (3 pages) | Cited 9 times

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Studies of the growth of GaSb self-assembled islands on GaAs and their morphological evolution for varying GaSb coverage are presented. Islands had a mean height of 15 nm and planar dimensions of 60 by 130 nm. Evolution of the island height, width and length shows that the island height and width increases rapidly in the first 2 s and then stabilizes, while the island length increases linearly. This behavior is interpreted using the theory by Tersoff and Tromp [Phys. Rev. Lett. 70, 2782 (1993)]. The volume growth was found to be initially faster than bulk growth. © 1998 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.35.Fx Diffusion; interface formation

Intrinsic microcrystalline silicon by plasma-enhanced chemical vapor deposition from dichlorosilane

R. Platz and S. Wagner

Appl. Phys. Lett. 73, 1236 (1998); http://dx.doi.org/10.1063/1.122138 (3 pages) | Cited 22 times

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Microcrystalline silicon (μc-Si:H) of truly intrinsic character can be deposited by plasma-enhanced chemical vapor deposition (PECVD) when dichlorosilane (SiH2Cl2) is added. A dark conductivity of 1.6×10−8 S/cm and an activation energy of 0.62 eV are obtained. No special gas purification or microdoping is required. SiH2Cl2 in small amounts has the additional effect of enhancing the crystallinity and reducing the oxygen incorporation by over a factor of 2. Sub-band-gap absorption spectroscopy indicates a low defect density. © 1998 American Institute of Physics.  
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81.05.Cy Elemental semiconductors
73.61.Cw Elemental semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.50.Pz Photoconduction and photovoltaic effects
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
78.40.Fy Semiconductors
61.72.-y Defects and impurities in crystals; microstructure
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Surface phases of GaAs and InAs (001) found in the metalorganic vapor-phase epitaxy environment

L. Li, B.-K. Han, and R. F. Hicks

Appl. Phys. Lett. 73, 1239 (1998); http://dx.doi.org/10.1063/1.122139 (3 pages) | Cited 3 times

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We have characterized the (2×4) and (4×2) reconstructions of GaAs and InAs (001) that are present in a metalorganic vapor-phase epitaxy (MOVPE) reactor. Scanning tunneling micrographs show that these surfaces are terminated with arsenic and gallium (or indium) dimers. The (2×4) dimer row exhibits a mottled appearance, which is ascribed to the adsorption of alkyl groups on some of the sites. On the (4×2), <10% of the surface is covered with small (2×4) islands. These results show that, in the MOVPE environment, the GaAs and InAs surface structures are nearly the same as those found in ultrahigh vacuum molecular beam epitaxy. © 1998 American Institute of Physics.
Show PACS
81.05.Ea III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.-a Thin film structure and morphology
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
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