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1 Sep 1997

Volume 71, Issue 9, pp. 1139-1277

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Thermally bonded planar waveguide lasers

C. T. A. Brown, C. L. Bonner, T. J. Warburton, D. P. Shepherd, A. C. Tropper, D. C. Hanna, and H. E. Meissner

Appl. Phys. Lett. 71, 1139 (1997); http://dx.doi.org/10.1063/1.119846 (3 pages) | Cited 18 times

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A new technique for fabricating active planar waveguide devices is reported. This process, based on the thermal bonding of precision finished crystal or glass components, allows waveguides to be assembled from very dissimilar materials and could be applied to a wide range of solid state laser or other optical media. The waveguide propagation losses, inferred from the laser performance, are found to be 0.7 dB/cm for Nd:Y3Al5O12 bonded to Y3Al5O12, Nd:Y3Al5O12 bonded to glass, and 0.4 dB/cm for Nd:Gd3Ga5O12 bonded to Y3Al5O12 devices. © 1997 American Institute of Physics.
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42.82.Cr Fabrication techniques; lithography, pattern transfer
42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.By Design of specific laser systems
42.82.Et Waveguides, couplers, and arrays

14.3 W quasicontinuous wave front-facet power from broad-waveguide Al-free 970 nm diode lasers

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

Appl. Phys. Lett. 71, 1142 (1997); http://dx.doi.org/10.1063/1.119847 (3 pages) | Cited 20 times

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Wide-stripe, 0.97 μm emitting Al-free InGaAs(P)/InGaP/GaAs broad-waveguide separate confinement heterostructure quantum-well lasers demonstrate a record value for quasicontinuous wave (QCW) output power: 14.3 W (100-μm-wide stripe, 100 μs-wide pulses); and reach catastrophic optical mirror damage (COMD) in QCW operation at an optical power density of 22.5 MW/cm2; that is, 40% higher than COMD levels in cw operation. The devices have low internal losses (αi = 1 cm−1) and high external differential quantum efficiency (86% for 2-mm-long lasers), and exhibit only 10–20 °C temperature rises in the active region at 10 W QCW power. We also show that long-cavity, large-contact-area devices exhibit relatively little spectral broadening with increased output power. © 1997 American Institute of Physics.  
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42.55.Px Semiconductor lasers; laser diodes

Enhanced luminance in polymer composite light emitting devices

S. A. Carter, J. C. Scott, and P. J. Brock

Appl. Phys. Lett. 71, 1145 (1997); http://dx.doi.org/10.1063/1.119848 (3 pages) | Cited 84 times

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We demonstrate that mixing insulating oxide nanoparticles into electroluminescent polymer materials results in increased current densities, radiances, and power efficiencies in polymer light emitting diode devices. For low driving voltages, an order of magnitude increase in current density and light output is achieved with minimal loss in device lifetime. At 5 V, we achieve radiances of 10 000 cd/m2 with external quantum efficiencies ∼1% for nanoparticle/MEH–PPV composite films. © 1997 American Institute of Physics.
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78.60.Fi Electroluminescence
85.60.Jb Light-emitting devices
78.66.Qn Polymers; organic compounds
78.66.Sq Composite materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials

Photonic crystal properties of packed submicrometric SiO2 spheres

H. Míguez, C. López, F. Meseguer, A. Blanco, L. Vázquez, R. Mayoral, M. Ocaña, V. Fornés, and A. Mifsud

Appl. Phys. Lett. 71, 1148 (1997); http://dx.doi.org/10.1063/1.119849 (3 pages) | Cited 151 times

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In this letter, we investigate the optical properties of packed monodisperse silica submicron spheres by means of optical transmission measurements. The results are compatible with a three dimensional face centered cubic order in these solid structures. The lattice parameter of these structures, and therefore their optical properties, can be easily tuned through the sphere size (between 200 and 700 nm) thus covering the whole visible and near infrared spectrum. © 1997 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.50.-p Quantum optics
78.30.Hv Other nonmetallic inorganics
78.40.Ha Other nonmetallic inorganics

Lithium–aluminum contacts for organic light-emitting devices

E. I. Haskal, A. Curioni, P. F. Seidler, and W. Andreoni

Appl. Phys. Lett. 71, 1151 (1997); http://dx.doi.org/10.1063/1.119850 (3 pages) | Cited 59 times

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Organic light-emitting devices have been prepared with multilayer Al–Li–Al cathodes in an ultrahigh vacuum molecular beam deposition system. The optimum device characteristics are obtained when there is a single Al layer separating the Li layer from the organic materials. Ab initio molecular dynamics calculations of the Al–Li interaction clarify the role of Al as a blocking layer to Li diffusion into the organic films as well as the behavior of the device when the thickness of this Al interfacial layer is changed. © 1997 American Institute of Physics.
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85.60.Jb Light-emitting devices
71.15.Pd Molecular dynamics calculations (Car-Parrinello) and other numerical simulations

Harmonic generation limitations in gain-switched semiconductor lasers due to distributed microwave effects

K. C. Sum and N. J. Gomes

Appl. Phys. Lett. 71, 1154 (1997); http://dx.doi.org/10.1063/1.119851 (2 pages) | Cited 3 times

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A large-signal, time domain semiconductor laser model that incorporates propagation effects within the cavity and a microwave circuit simulator are used to investigate distributed microwave effects on gain-switching performance. It is shown that the position of the feed point to the top electrode can have a significant influence on the harmonic content of the generated pulses, which is an important consideration in microwave/millimeter-wave signal generation schemes. © 1997 American Institute of Physics.  
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42.55.Px Semiconductor lasers; laser diodes
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
84.40.Ik Masers; gyrotrons (cyclotron-resonance masers)
42.60.Fc Modulation, tuning, and mode locking
85.30.De Semiconductor-device characterization, design, and modeling

Tailoring of trap-related carrier dynamics in low-temperature-grown GaAs

P. W. E Smith, S. D. Benjamin, and H. S. Loka

Appl. Phys. Lett. 71, 1156 (1997); http://dx.doi.org/10.1063/1.119852 (3 pages) | Cited 6 times

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In this letter, we present the results of an experimental study of low-temperature-grown GaAs, which clearly resolves separately both carrier trapping and recombination processes. We extend our previous model to account for the observed carrier dynamics, and show how the material growth and annealing conditions can be adjusted to optimize the material properties for all-optical device applications. © 1997 American Institute of Physics.
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72.80.Ey III-V and II-VI semiconductors
81.05.Ea III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
71.55.Eq III-V semiconductors
61.72.Cc Kinetics of defect formation and annealing
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Phase stability of guest/host photorefractive polymers studied by light scattering experiments

E. Hendrickx, B. L. Volodin, D. D. Steele, J. L. Maldonado, J. F. Wang, B. Kippelen, and N. Peyghambarian

Appl. Phys. Lett. 71, 1159 (1997); http://dx.doi.org/10.1063/1.119612 (3 pages) | Cited 20 times

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We report on light scattering measurements in guest/host photorefractive polymers doped with different polar dyes as a function of temperature and sample composition. Crystallization processes of the polar dye are found to follow a nucleation and growth mechanism. The structure and melting point of the polar dye, the storage temperature, and the amount of plasticizer are shown to exert a major influence on the shelf lifetime of the samples. New composites with high efficiency and long shelf lifetime are presented. © 1997 American Institute of Physics.
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42.70.Jk Polymers and organics
42.70.Gi Light-sensitive materials
78.35.+c Brillouin and Rayleigh scattering; other light scattering
61.41.+e Polymers, elastomers, and plastics
64.70.D- Solid-liquid transitions
64.60.Q- Nucleation
64.70.K- Solid-solid transitions
78.20.-e Optical properties of bulk materials and thin films

Orientational holographic grating observed in liquid crystals sandwiched with photoconductive polymer films

Hiroshi Ono and Nobuhiro Kawatsuki

Appl. Phys. Lett. 71, 1162 (1997); http://dx.doi.org/10.1063/1.119613 (3 pages) | Cited 33 times

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We presented a novel type of orientational photorefractive device, consisting of liquid crystals (LCs) sandwiched with photoconductive polymer films across the insulated polymer films. The photoexcited charges were generated in the photoconductive layers and eventually become trapped in the dark areas at the insulated polymer surfaces. The resulting space charge field reoriented the LC molecules and the holographic gratings were generated. The strong beam coupling effects were observed and the refractive index modulation Δn was estimated to be of the order of 3.6×10−3. © 1997 American Institute of Physics.
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42.70.Df Liquid crystals
42.70.Jk Polymers and organics
42.70.Gi Light-sensitive materials
42.40.Eq Holographic optical elements; holographic gratings
85.60.-q Optoelectronic devices
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials

Microdischarge devices fabricated in silicon

J. W. Frame, D. J. Wheeler, T. A. DeTemple, and J. G. Eden

Appl. Phys. Lett. 71, 1165 (1997); http://dx.doi.org/10.1063/1.119614 (3 pages) | Cited 73 times

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Cylindrical microdischarge cavities 200–400 μm in diameter and 0.5–5 mm in depth have been fabricated in silicon and operated at room temperature with neon or nitrogen at specific power loadings beyond 10 kW/cm3. The discharges are azimuthally uniform and stable operation at N2 and Ne pressures exceeding 1 atm and ∼ 600 Torr, respectively, has been realized for 400 μm diameter devices. Spectroscopic measurements on neon discharges demonstrate that the device behaves as a hollow cathode discharge for pressures >50 Torr. As evidenced by emission from Ne and Ne+ (2P,2F) states as well as N2 (C→B) fluorescence (316–492 nm), these discharge devices are intense sources of ultraviolet and visible radiation and are suitable for fabrication as arrays. © 1997 American Institute of Physics.
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84.47.+w Vacuum tubes
42.72.Bj Visible and ultraviolet sources

Cr K edge x-ray absorption study of Cr dopants in Mg2SiO4 and Ca2GeO4

K. E. Miyano, J. C. Woicik, P. Sujatha Devi, and H. D. Gafney

Appl. Phys. Lett. 71, 1168 (1997); http://dx.doi.org/10.1063/1.119615 (3 pages) | Cited 4 times

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X-ray absorption above the Cr K edge has been used to study two Cr-doped olivine-structure materials. For Mg2SiO4, the extended fine structure shows that Cr resides in octahedral and tetrahedral sites with Cr–O distances of 1.98±0.03 and 1.68±0.03 Å, while the near edge structure indicates that Cr is in 3+ and 4+ oxidation states. For Ca2GeO4, site-size constraints limit Cr to the tetrahedral site with a Cr–O distance of 1.745±0.02 Å, and this Cr is only in the 4+ oxidation state. This study illustrates the utility of x-ray absorption for probing and relating the oxidation states and sites of constituent elements. In this specific case of Cr in olivine hosts, such understanding is critical to the development of these materials as tunable infrared solid-state lasers: Cr in the 4+ state provides the desired emission centered near 1.3 μm. © 1997 American Institute of Physics.
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78.70.Dm X-ray absorption spectra
61.72.S- Impurities in crystals
42.70.Hj Laser materials

Growth mechanisms of epitaxial metallic oxide SrRuO3 thin films studied by scanning tunneling microscopy

R. A. Rao, Q. Gan, and C. B. Eom

Appl. Phys. Lett. 71, 1171 (1997); http://dx.doi.org/10.1063/1.119616 (3 pages) | Cited 55 times

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We report the deliberately controlled growth of epitaxial metallic oxide SrRuO3 thin films in three distinctly different growth modes. Scanning tunneling microscopy and x-ray diffraction indicate that the growth mechanism for films on exact (001) SrTiO3 substrates is two-dimensional nucleation, which results in a two domain in-plane structure. As the miscut angle of vicinal (001) SrTiO3 substrates is increased, the growth mechanism changes to step flow which leads to single domain thin films. Films on (001) LaAlO3 substrates have an incoherent three-dimensional island growth due to the large lattice mismatch, resulting in a bulk-like lattice. The vast difference in the growth mechanisms of these films leads to a corresponding difference in their electrical transport and magnetic behavior. Such nanoscale control of growth mechanism, surface morphology, and domain structure can be very important in the fabrication of novel perovskite oxide devices. © 1997 American Institute of Physics.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
75.70.Ak Magnetic properties of monolayers and thin films
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
75.60.Ch Domain walls and domain structure
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.50.Dd Nonmetallic ferromagnetic materials

Mechanism for ordering in SiGe films with reconstructed surface

T. Araki, N Fujimura, and T. Ito

Appl. Phys. Lett. 71, 1174 (1997); http://dx.doi.org/10.1063/1.119617 (3 pages) | Cited 2 times

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A model of the ordering mechanism in SiGe films is developed to explain the occurrence of two types of ordered structures. We investigate the stability of ordered structures by strain energy calculation. It is suggested that atomic diffusion, which is enhanced by strain in a film, influences the formation of ordered structures. The process of atomic exchange that forms the ordered structure at a reconstructed surface during growth is also discussed. © 1997 American Institute of Physics.  
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68.55.-a Thin film structure and morphology
81.05.Hd Other semiconductors
68.35.Rh Phase transitions and critical phenomena

Ultrasound induced lubricity in microscopic contact

F. Dinelli, S. K. Biswas, G. A. D. Briggs, and O. V. Kolosov

Appl. Phys. Lett. 71, 1177 (1997); http://dx.doi.org/10.1063/1.120417 (3 pages) | Cited 27 times

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A physical effect of ultrasound induced lubricity is reported. We studied the dynamic friction dependence on out-of-plane ultrasonic vibration of a sample using friction force microscopy and a scanning probe technique, the ultrasonic force microscope, which can probe the dynamics of the tip–sample elastic contact at a submicrosecond scale. The results show that friction vanishes when the tip–surface contact breaks for part of the out-of-plane vibration cycle. Moreover, the friction force reduces well before such a break, and this reduction does not depend on the normal load. This suggests the presence on the surface of a layer with viscoelastic behavior. © 1997 American Institute of Physics.
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46.55.+d Tribology and mechanical contacts
62.20.Qp Friction, tribology, and hardness
07.64.+z Acoustic instruments and equipment

Transmission ellipsometry of a thin-film helicoidal bianisotropic medium

P. I. Rovira, R. A. Yarussi, R. W. Collins, R. Messier, V. C. Venugopal, A. Lakhtakia, K. Robbie, and M. J. Brett

Appl. Phys. Lett. 71, 1180 (1997); http://dx.doi.org/10.1063/1.119618 (3 pages) | Cited 23 times

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Experimental evidence is introduced for circularly birefringent and dichroic behavior in a MgF2 thin-film helicoidal bianisotropic medium (TFHBM), which is a rotationally inhomogeneous and anisotropic material. Optical rotation (OR) of an incident linearly polarized monochromatic plane wave is observed upon transmission through the MgF2/glass TFHBM/substrate system, and it is accompanied by an ellipticity in the polarization of the transmitted plane wave. Both OR and ellipticity spectra have remarkable features within a narrow wavelength zone not unlike the Cotton effect in isotropic chiral media. The features in the experimental spectra are in accord with theoretical predictions. © 1997 American Institute of Physics.
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78.66.Nk Insulators
78.20.Fm Birefringence
78.20.Ek Optical activity
42.79.Wc Optical coatings

Intersubband photoluminescence of GaAs quantum wells under selective interband excitation

S. Sauvage, P. Boucaud, F. H. Julien, O. Gauthier-Lafaye, V. Berger, and J. Nagle

Appl. Phys. Lett. 71, 1183 (1997); http://dx.doi.org/10.1063/1.119619 (3 pages) | Cited 6 times

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We report on infrared spontaneous emission between subbands in GaAs quantum wells excited by an interband optical pumping. The active region consists of 15 periods of four coupled quantum wells which are embedded in a mid-infrared optical waveguide. Electrons are selectively injected from the valence band in the excited subbands of the quantum wells using interband optical pumping. Intersubband spontaneous emission is observed at low temperature between the E5 and E4 subbands of the quantum wells (E5−E4 ≈ 162 meV ≈ 7.7 μm). The intersubband luminescence vanishes when the E5 subband is not selectively populated. The emission is polarized along the growth axis of the quantum wells as expected for intersubband transitions. The collected infrared power exhibits a linear dependence with the interband optical power with a slope ≈ 560 pW/W. © 1997 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
42.50.-p Quantum optics
42.79.Gn Optical waveguides and couplers
42.55.Px Semiconductor lasers; laser diodes

Boron acceptor levels in 6H-SiC bulk samples

A. O. Evwaraye, S. R. Smith, W. C. Mitchel, and H. McD. Hobgood

Appl. Phys. Lett. 71, 1186 (1997); http://dx.doi.org/10.1063/1.119620 (3 pages) | Cited 9 times

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Thermal admittance spectroscopy has been used to determine the ground-state energies of the boron impurity in 6H-SiC. The background doping, NA−ND, of the samples used in this study ranged from 3×1016 to 1×1018 cm−3. From electron spin resonance studies, it is known that boron substitutes for silicon in the silicon carbide lattice occupying three inequivalent sites. Using admittance spectroscopy the ground state energies of Ev+0.27 eV, Ev+0.31 eV, and Ev+0.38 eV were determined for the shallow boron acceptor in 6H-SiC. The free carrier concentration does not appear to be the only determining factor for which the boron acceptor level is observed. © 1997 American Institute of Physics.
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71.55.Ht Other nonmetals

Quantum confinement in amorphous silicon layers

G. Allan, C. Delerue, and M. Lannoo

Appl. Phys. Lett. 71, 1189 (1997); http://dx.doi.org/10.1063/1.119621 (3 pages) | Cited 19 times

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The electronic structure of hydrogenated amorphous silicon layers is calculated within the empirical tight binding approximation. We predict an important blueshift due to the confinement for layer thickness below 3 nm, and we compare with crystalline silicon layers. The radiative recombination rate is enhanced by the disorder and the confinement but remains much weaker than that in direct band gap semiconductors. The comparison of our results with experimental data shows that the density of defects and localized states in the studied samples is quite small. © 1997 American Institute of Physics.
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73.23.-b Electronic transport in mesoscopic systems
72.80.Cw Elemental semiconductors
71.23.Cq Amorphous semiconductors, metallic glasses, glasses
72.80.Ng Disordered solids
71.55.Cn Elemental semiconductors
71.55.Jv Disordered structures; amorphous and glassy solids
73.20.Fz Weak or Anderson localization
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

ZnSe epitaxy on a GaAs(110) surface

S. Miwa, L. H. Kuo, K. Kimura, A. Ohtake, T. Yasuda, C. G. Jin, and T. Yao

Appl. Phys. Lett. 71, 1192 (1997); http://dx.doi.org/10.1063/1.119622 (3 pages) | Cited 5 times

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ZnSe molecular beam epitaxial growth on GaAs(110) substrates has been studied using reflection high-energy electron diffraction (RHEED), atomic force microscopy, and transmission electron microscopy. An atomically flat and low defect homoepitaxial buffer GaAs(110) was grown with high V/III ratio ( ≥ 150) and at low growth temperature ( ∼ 430 °C). At the beginning of ZnSe growth on a GaAs(110) buffer epitaxial layer, RHEED oscillation was observed and no facet was seen on a pseudomorphic ZnSe(110) surface. Low defect ZnSe films (defect density ⩽ 105 cm−2) were also obtained without the Zn preexposure process necessary for low defect ZnSe(001) growth. © 1997 American Institute of Physics.
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81.05.Dz II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Ge nanocrystals in SiO2 films

Takamitsu Kobayashi, Toshiaki Endoh, Hisashi Fukuda, Shigeru Nomura, Akira Sakai, and Yuji Ueda

Appl. Phys. Lett. 71, 1195 (1997); http://dx.doi.org/10.1063/1.119623 (3 pages) | Cited 34 times

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SiO2/Ge nanocrystal/SiO2 structures have been fabricated by deposition of Ge film on a SiO2 layer and subsequent oxidation of the structure at a temperature between 800 °C and 1000 °C. Secondary ion mass spectrometry results indicate that the Ge precipitates into the bulk SiO2 at a density of 1×1012 cm−2. Raman spectra show a sharp peak at 300 cm−1 for the nanocrystallized Ge. The nanocrystal diameter is determined to be 5 nm on average. In the metal–insulator–silicon structure, electron storage occurs in the SiO2/Ge/SiO2 potential well via electron tunneling into the oxide film. Capacitance-voltage measurements indicate that flatband voltage (VFB) shifts to 0.91 V after the electron injection. The VFB shift is attributed to the charge storing for a single electron per potential well.© 1997 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.65.Mq Oxidation
68.35.Ct Interface structure and roughness
64.75.-g Phase equilibria
81.30.Mh Solid-phase precipitation
78.30.Am Elemental semiconductors and insulators
78.66.Db Elemental semiconductors and insulators
78.66.Jg Amorphous semiconductors; glasses

1.54 μm photoluminescence of Er3+ doped into SiO2 films containing Si nanocrystals: Evidence for energy transfer from Si nanocrystals to Er3+

Minoru Fujii, Masato Yoshida, Yoshihiko Kanzawa, Shinji Hayashi, and Keiichi Yamamoto

Appl. Phys. Lett. 71, 1198 (1997); http://dx.doi.org/10.1063/1.119624 (3 pages) | Cited 35 times

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SiO2 films containing Si nanocrystals (nc-Si) and Er were prepared and their photoluminescence (PL) properties were studied. The samples exhibited luminescence peaks at 0.81 and 1.54 μm, which could be assigned to the electron-hole recombination in nc-Si and the intra-4f transition in Er3+, respectively. Correlation between the intensities of the two luminescence peaks was studied as functions of Er concentration and excitation power. The present results clearly demonstrate that excitation of Er3+ occurs through the recombination of photogenerated carriers spatially confined in nc-Si and the subsequent energy transfer to Er3+. © 1997 American Institute of Physics.
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78.66.Jg Amorphous semiconductors; glasses
78.55.Hx Other solid inorganic materials

Lithographic positioning of self-assembled Ge islands on Si(001)

T. I. Kamins and R. Stanley Williams

Appl. Phys. Lett. 71, 1201 (1997); http://dx.doi.org/10.1063/1.119625 (3 pages) | Cited 103 times

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Ge islands were deposited on Si(001) partially covered with patterned oxide. Selective Si was deposited on some wafers before Ge deposition to form raised Si(001) plateaus with well-defined sidewall facets. On narrow lines, the Ge islands locate preferentially at the edges of the raised Si(001) regions, and the preference is strongest on the narrowest patterns aligned along a 〈100〉 direction. For a 450 nm wide plateau aligned in this direction, all the islands are positioned along the edges of the pattern, with a 300 nm space near the center of the pattern free of Ge islands. The islands appear to be uniformly spaced along the pattern edges. On wider lines, several rows of islands are aligned near the edges of the pattern, with the order decreasing farther from the edge. © 1997 American Institute of Physics.
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81.05.Cy Elemental semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
85.40.Hp Lithography, masks and pattern transfer
81.65.Mq Oxidation
81.65.Cf Surface cleaning, etching, patterning
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.-a Thin film structure and morphology

Anisotropic epitaxial lateral growth in GaN selective area epitaxy

D. Kapolnek, S. Keller, R. Vetury, R. D. Underwood, P. Kozodoy, S. P. Den Baars, and U. K. Mishra

Appl. Phys. Lett. 71, 1204 (1997); http://dx.doi.org/10.1063/1.119626 (3 pages) | Cited 135 times

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Epitaxial lateral mask overgrowth which occurs during GaN selective epitaxy has been studied using linear mask features. The lateral growth varies between its maximum and minimum over a 30° angular span and exhibits hexagonal symmetry. Vertical growth follows an opposite trend, with lateral growth maxima, and vertical growth minima occurring for lines parallel to the GaN 〈10•0〉. Large variations in the lateral growth are also obtained through variations in the growth temperature and NH3 flow. Under proper growth conditions, lateral to vertical growth rate ratios of up to 4.1 can be achieved, resulting in significant lateral mask overgrowth and coalescence of features without excessive growth times. © 1997 American Institute of Physics.
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81.05.Ea III-V semiconductors
68.55.-a Thin film structure and morphology
81.15.Kk Vapor phase epitaxy; growth from vapor phase
85.40.Hp Lithography, masks and pattern transfer

Three types of stable structures of hydrogenated silicon clusters

M. O. Watanabe, H. Murakami, T. Miyazaki, and T. Kanayama

Appl. Phys. Lett. 71, 1207 (1997); http://dx.doi.org/10.1063/1.120452 (3 pages) | Cited 17 times

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We have studied stable structures of hydrogenated Si clusters grown from silane gas in an ion trap developed for cluster growth. The grown clusters were extracted from the ion trap through two different pathways and were analyzed by mass spectrometers. The Si6Hx+ cations were stably grown, among them clusters with x = 1, 7, and 13 were always observed, regardless of the growth conditions or the extraction pathways. The stable structures of these clusters were theoretically investigated. Clusters of x = 1, 7, and 13 corresponded to the compact structure, the intermediate structure which has both compact and bulklike configurations, and the bulklike sp3 structure, respectively. © 1997 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
36.40.Mr Spectroscopy and geometrical structure of clusters

Minority-carrier characteristics of SiNx/GaAs metal–insulator–semiconductor structures with Si/Ge interlayers

Dae-Gyu Park, J. C. Reed, and Hadis Morkoç

Appl. Phys. Lett. 71, 1210 (1997); http://dx.doi.org/10.1063/1.119853 (3 pages) | Cited 8 times

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Minority-carrier response and conductance loss characteristics of SiNx/Si/Ge/n-GaAs(001) metal–insulator–semiconductor (MIS) structures are presented. The response time of minority carriers with Si( ⩽ 10 Å)/Ge (20 Å) interlayers, as determined by the capacitance–voltage (C–V) method, is several orders of magnitude smaller than those with Si interlayers only. The minority carriers in n-type Si/Ge/GaAs layers respond to even a small ac signal of 1 kHz at room temperature, which is ascribed to the smaller band gap and thus a higher intrinsic carrier concentration of Ge. The minority carriers in the SiNx/Si/Ge/n-GaAs MIS structures respond to a 1 MHz signal at a sample temperature of 230 °C. Temperature-dependent C–V measurements on the GaAs MIS structure with Si/Ge, interlayers revealed the activation energy (Ea) of the minority-carrier recombination to be about 0.58 eV. The conductance loss characteristics of SiNx/Si/Ge/GaAs structures indicate a contribution by interface traps responding to slow states, while the fast states are a result of interface defects of the SiNx/Si/GaAs MIS system. © 1997 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.61.Ey III-V semiconductors
73.61.Cw Elemental semiconductors
73.20.At Surface states, band structure, electron density of states
68.35.Ct Interface structure and roughness
73.25.+i Surface conductivity and carrier phenomena
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