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26 Apr 1999

Volume 74, Issue 17, pp. 2405-2555

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Theoretical transport studies of p-type GaN/AlGaN modulation-doped heterostructures

L. Hsu and W. Walukiewicz

Appl. Phys. Lett. 74, 2405 (1999); http://dx.doi.org/10.1063/1.123897 (3 pages) | Cited 15 times

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We have calculated hole transfer and low-temperature mobilities in p-type GaN/AlGaN modulation-doped heterostructures. Although substantial p-type conduction is difficult to achieve in bulk nitrides, the strain-induced polarization field can greatly enhance the transfer of holes from relatively deep Mg acceptors in the AlGaN barrier into the GaN well. The calculations predict formation of a two-dimensional hole gas with densities greater than 1012 cm−2 and with low-temperature mobilities in excess of 104 cm2/V s. © 1999 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Spontaneous lifetime control in a native-oxide-apertured microcavity

L. A. Graham, D. L. Huffaker, and D. G. Deppe

Appl. Phys. Lett. 74, 2408 (1999); http://dx.doi.org/10.1063/1.123863 (3 pages) | Cited 53 times

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Spontaneous lifetime control is demonstrated using very small apertured microcavities, with quantum-dot light emitters used to obtain electronic confinement within the aperture. A factor of 2.3 increase in the averaged spontaneous emission rate is achieved due to the optical confinement. The enhancement/inhibition ratio of the spontaneous emission rate tracks the optical mode size and spectral response of the apertured microcavity. © 1999 American Institute of Physics.
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78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
85.60.Jb Light-emitting devices

InAs-doped silica films for saturable absorber applications

I. P. Bilinsky, J. G. Fujimoto, J. N. Walpole, and L. J. Missaggia

Appl. Phys. Lett. 74, 2411 (1999); http://dx.doi.org/10.1063/1.123864 (3 pages) | Cited 6 times

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InAs-doped thin silica films having saturable absorption properties were fabricated using rf sputtering. The films contain semiconductor nanoparticles preserving the zincblende crystal structure of bulk InAs. We have investigated the linear and nonlinear optical as well as structural properties of the films. Rapid thermal annealing in nitrogen was successfully used to tailor the optical absorption saturation dynamics. The films having saturable absorber properties were applied to Kerr lens mode locking initiation in a Ti:Al2O3 laser resulting in self-starting mode locking operation with pulses as short as 25 fs. © 1999 American Institute of Physics.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
78.66.Nk Insulators
42.60.Fc Modulation, tuning, and mode locking
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.55.Rz Doped-insulator lasers and other solid state lasers
78.40.Ha Other nonmetallic inorganics
81.15.Cd Deposition by sputtering
68.55.-a Thin film structure and morphology
61.72.Cc Kinetics of defect formation and annealing

Direct view of stress distribution in solid by mechanoluminescence

Chao-Nan Xu, Tadahiko Watanabe, Morito Akiyama, and Xu-Guang Zheng

Appl. Phys. Lett. 74, 2414 (1999); http://dx.doi.org/10.1063/1.123865 (3 pages) | Cited 102 times

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Visualization of stress distribution has been realized by a nondestructive mechanoluminescence (ML) from SrAl2O4:Eu, which can emit three magnitudes higher visible light than that of well-known ML substance of quartz. A simulation result confirms that such a ML image successfully reflects the stress distribution. A kinetic model for ML of SrAl2O4:Eu is proposed. © 1999 American Institute of Physics.
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78.60.Mq Sonoluminescence, triboluminescence
46.80.+j Measurement methods and techniques in continuum mechanics of solids
81.70.Fy Nondestructive testing: optical methods

Enhanced electro-optic response of layered composite materials

Robert L. Nelson and Robert W. Boyd

Appl. Phys. Lett. 74, 2417 (1999); http://dx.doi.org/10.1063/1.123866 (3 pages) | Cited 13 times

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We have constructed a multilayered composite material consisting of alternating layers of rf-sputtered barium titanate and spin-coated polycarbonate containing a third-order nonlinear optical organic dopant. The effective nonlinear susceptibility of the composite describing the quadratic electro-optic effect was measured to have the value χ(3) = (3.2+0.2i)×10−21±25% (m/V)2. The real part of this value is a factor of 3.2±50% times larger than that of the doped polycarbonate, which is the dominant electro-optic component of the composite. We have modeled the experiment by using both effective medium theory and by solving the wave equation for our multilayered system, and we find that these approaches give consistent predictions which are in good agreement to the experimental results. © 1999 American Institute of Physics.
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78.20.Jq Electro-optical effects
78.66.Qn Polymers; organic compounds
42.70.Jk Polymers and organics
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.65.An Optical susceptibility, hyperpolarizability

Defect-related infrared photoluminescence in Ge+-implanted SiO2 films

X. L. Wu, T. Gao, G. G. Siu, S. Tong, and X. M. Bao

Appl. Phys. Lett. 74, 2420 (1999); http://dx.doi.org/10.1063/1.123867 (3 pages) | Cited 24 times

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SiO2 films with Ge+ implantation at an energy of 60 keV and a dose of 1×1016 cm−2, followed by annealing at different temperature, exhibit a broad infrared photoluminescence (PL) at room temperature under an excitation of the 514.5 nm line of Ar+ laser. With increasing the annealing temperature, the intensity of the infrared PL band decreases, its full width at half maximum increases, and its energy redshifts. Spectral analysis and some experimental results from Raman scattering, electron spin resonance, and infrared spectroscopy strongly suggest that the infrared PL is mainly related to interfacial oxygen-deficient-type defects between the oxide and Ge nanocrystals. © 1999 American Institute of Physics.
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78.66.Nk Insulators
78.55.Hx Other solid inorganic materials
71.55.Ht Other nonmetals
61.80.Jh Ion radiation effects
61.72.up Other materials
61.82.Ms Insulators
73.20.Hb Impurity and defect levels; energy states of adsorbed species
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Cc Kinetics of defect formation and annealing
78.30.Hv Other nonmetallic inorganics
76.30.Mi Color centers and other defects

Thermal poling of silica in air and under vacuum: The influence of charge transport on second harmonic generation

V. Pruneri, F. Samoggia, G. Bonfrate, P. G. Kazansky, and G. M. Yang

Appl. Phys. Lett. 74, 2423 (1999); http://dx.doi.org/10.1063/1.123868 (3 pages) | Cited 21 times

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A comparison between thermal poling of silica in air and in vacuum is reported. It is shown that the second-order susceptibility and thickness of the nonlinear layer as well as their time evolution are highly dependent on the surrounding poling atmosphere. In the vacuum case a charge distribution (under the anode) more complex and broader than that for the air case has also been revealed by laser induced pressure pulse measurements. A multiple charge carrier model can explain the formation and evolution of the depletion region under the anode. The findings are relevant to achieve improved nonlinearities in fiber and waveguide devices. © 1999 American Institute of Physics.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.An Optical susceptibility, hyperpolarizability
77.22.Jp Dielectric breakdown and space-charge effects
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High voltage sheath behavior in a drifting plasma

I. G. Brown, O. R. Monteiro, and M. M. M. Bilek

Appl. Phys. Lett. 74, 2426 (1999); http://dx.doi.org/10.1063/1.123869 (3 pages) | Cited 14 times

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We describe a simple experiment in which a high voltage substrate is immersed in a streaming, vacuum-arc-produced, titanium plasma. We show that high substrate voltages that are orders of magnitude greater than the electron temperature can be sustained, effectively on a direct current basis, by a well-rounded substrate (no sharp points or edges) immersed in the plasma stream, for the case of a plasma with density not too low (greater than about 109 cm−3) and with drift velocity that is equal to or greater than the sheath propagation speed, typically of order the ion acoustic speed. This result is significant not only from a basic plasma physics perspective, but also for the technology of carrying out plasma immersion surface processing. © 1999 American Institute of Physics.
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52.40.Hf Plasma-material interactions; boundary layer effects
52.25.Fi Transport properties
52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.80.Vp Discharge in vacuum
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Kinetics of surface-state laser annealing in Si by frequency-swept infrared photothermal radiometry

Mario E. Rodriguez, J. A. Garcia, A. Mandelis, C. Jean, and Y. Riopel

Appl. Phys. Lett. 74, 2429 (1999); http://dx.doi.org/10.1063/1.123870 (3 pages) | Cited 7 times

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Frequency-swept (“chirped”) infrared photothermal radiometry was combined with conventional single-frequency modulation of an Ar ion laser beam to yield a quantitative study of the surface-state annealing processes induced by the low-fluence laser beam on n- and p-type Si wafers. The appearance of a signal transient was found to be strongly dependent on the electronic quality of the wafer surface and was absent in the thermally oxidized p-Si wafer. The low-injection minority-carrier lifetimes and diffusion coefficients were not affected by the laser-surface interaction, but the surface recombination velocity strongly decreased with time of exposure. A two-trap rate model was advanced to explain the transient behavior in terms of surface-state annealing and carrier ejection. © 1999 American Institute of Physics.
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73.20.At Surface states, band structure, electron density of states
73.25.+i Surface conductivity and carrier phenomena
61.72.Cc Kinetics of defect formation and annealing
61.82.Fk Semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Cw Elemental semiconductors
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects

Accommodation of nonstoichiometry in (100) fiber-textured (BaxSr1−x)Ti1+yO3+z thin films grown by chemical vapor deposition

Susanne Stemmer, S. K. Streiffer, Nigel D. Browning, and Angus I. Kingon

Appl. Phys. Lett. 74, 2432 (1999); http://dx.doi.org/10.1063/1.123871 (3 pages) | Cited 22 times

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We have investigated the microstructural accommodation of nonstoichiometry in (BaxSr1−x)Ti1+yO3+z thin films grown by chemical vapor deposition. Films with y=0.04 and y=0.15 were studied by high-spatial resolution electron energy-loss spectroscopy, revealing changes in chemistry and local atomic environment both at grain boundaries and within grains as a function of titanium content. We find that excess titanium in the samples with y=0.15 segregates to the grain boundaries in addition to being partially accommodated in the grain interior. © 1999 American Institute of Physics.
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68.55.Nq Composition and phase identification
68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
64.75.-g Phase equilibria
61.72.Mm Grain and twin boundaries
81.30.Mh Solid-phase precipitation
79.20.Kz Other electron-impact emission phenomena

Boron-enhanced diffusion of boron from ultralow-energy ion implantation

Aditya Agarwal, H.-J. Gossmann, D. J. Eaglesham, S. B. Herner, A. T. Fiory, and T. E. Haynes

Appl. Phys. Lett. 74, 2435 (1999); http://dx.doi.org/10.1063/1.123872 (3 pages) | Cited 43 times

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We have investigated the diffusion enhancement mechanism of boron-enhanced diffusion (BED), wherein boron diffusivity is enhanced four to five times over the equilibrium diffusivity at 1050 °C in the proximity of a silicon layer containing a high boron concentration. It is demonstrated that BED is driven by excess interstitials injected from the high boron concentration layer during annealing. For evaporated layers, BED is observed above a threshold boron concentration between 1% and 10%, though it appears to be closer to 1% for B-implanted layers. For sub-keV B implants above the threshold, BED dominates over the contribution from transient-enhanced diffusion to junction depth. For 0.5 keV B, this threshold implantation dose lies between 3×1014 and 1×1015 cm−2. It is proposed that the excess interstitials responsible for BED are produced during the formation of a silicon boride phase in the high B concentration layers. © 1999 American Institute of Physics.
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61.72.uf Ge and Si
66.30.J- Diffusion of impurities
61.72.J- Point defects and defect clusters
61.82.Fk Semiconductors
81.05.Cy Elemental semiconductors

Photogeneration of high pretilt angles of nematic liquid crystals by azobenzene-containing polymer films

Seiichi Furumi, Masaru Nakagawa, Shin’ya Morino, Kunihiro Ichimura, and Hidehiko Ogasawara

Appl. Phys. Lett. 74, 2438 (1999); http://dx.doi.org/10.1063/1.123873 (3 pages) | Cited 19 times

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A vertically aligned (VA) type of nematic liquid-crystal (LC) cell was explored using photoirradiated thin films of a polymethacrylate with mesogenic moieties of 4-trifluoromethoxyazobenzene as side chains. Optical anisotropy was generated by slantwise irradiation of films of the polymer with nonpolarized ultraviolet light, followed by annealing treatment to enhance the photodichroism which displayed thermal stability. The photoirradiated films brought about high pretilt angles of the LC so that a VA-type LC cell was fabricated. The cell exhibited electro-optical properties with excellent optical quality on applying voltages even after heating at 100 °C for several hours. © 1999 American Institute of Physics.
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61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order
78.20.Jq Electro-optical effects
42.79.Kr Display devices, liquid-crystal devices
82.50.Bc Processes caused by infrared radiation
82.50.Hp Processes caused by visible and UV light
42.70.Df Liquid crystals
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
78.20.Fm Birefringence

Electrical isolation of GaN by ion implantation damage: Experiment and model

C. Uzan-Saguy, J. Salzman, R. Kalish, V. Richter, U. Tish, S. Zamir, and S. Prawer

Appl. Phys. Lett. 74, 2441 (1999); http://dx.doi.org/10.1063/1.123874 (3 pages) | Cited 21 times

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Electrical and optical isolation of unintentionally doped GaN layers due to the damage created by H+ and He+ ions passing through the layer are demonstrated. As a result of the irradiation, the sample resistance increases by 11 orders of magnitude and the band-to-band photoluminescence (PL) emission is totally quenched. Following annealing (1000 °C, 30 s), the conductivity can be nearly completely recovered, whereas only partial recovery of the PL emission is obtained. A model is proposed which invokes the presence of potential barriers for electronic transport across extended defects as the major factor limiting carrier mobility. Radiation defects increase these barriers, thus affecting the sample resistivity. This model fits the experimental results for both H and He induced damage extremely well and thus proves that defects created by nuclear collisions of the ions traversing the layer are responsible for the observed effects. © 1999 American Institute of Physics.
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61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
71.55.Eq III-V semiconductors
78.55.Cr III-V semiconductors
72.80.Ey III-V and II-VI semiconductors
61.72.uj III-V and II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Cc Kinetics of defect formation and annealing
73.50.Dn Low-field transport and mobility; piezoresistance
61.72.Nn Stacking faults and other planar or extended defects

Direct evidence of Cd diffusion into Cu(In, Ga)Se2 thin films during chemical-bath deposition process of CdS films

T. Nakada and A. Kunioka

Appl. Phys. Lett. 74, 2444 (1999); http://dx.doi.org/10.1063/1.123875 (3 pages) | Cited 47 times

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The diffusion behavior at the Cu(In, Ga)Se2 (CIGS)/CdS interface of high efficiency CIGS thin film solar cells has been investigated using energy dispersive x-ray spectroscopy (EDX) and transmission electron microscopy. CdS layers were deposited on CIGS thin films using the chemical bath deposition (CBD) process. EDX analysis revealed that Cd was present in the CIGS layer approximately 100 Å from the interface boundary. In contrast to the diffusion of Cd, the Cu concentration decreased near the surface of the CIGS film, suggesting substitution of Cd for Cu atoms. These results are direct evidence of Cd diffusion into CIGS thin films during the CBD process. © 1999 American Institute of Physics.  
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68.35.Fx Diffusion; interface formation
68.35.Ct Interface structure and roughness
84.60.Jt Photoelectric conversion
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
81.05.Hd Other semiconductors
81.05.Dz II-VI semiconductors
66.30.J- Diffusion of impurities
68.55.-a Thin film structure and morphology
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods

Variation of nonlinearity parameter at low fundamental amplitudes

Daniel J. Barnard

Appl. Phys. Lett. 74, 2447 (1999); http://dx.doi.org/10.1063/1.123876 (3 pages) | Cited 8 times

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Recent harmonic generation measurements of the nonlinearity parameter β in polycrystalline Cu–Al alloys have shown a transition to lower values at low fundamental amplitude levels. Values for β at high (>10 Å) fundamental levels are in the range predicted by single-crystal second- and third-order elastic constants while lower fundamental levels (<4 Å) produce values that are a fraction of those predicted. The effect is believed genuine and has been demonstrated recently in a commercial aluminum alloy by others. The source of the effect is unclear but initial results may require a reexamination of current methods for measurement of third-order elastic constants. © 1999 American Institute of Physics.
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43.25.Dc Nonlinear acoustics of solids
62.65.+k Acoustical properties of solids
62.20.D- Elasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations

Growth of a single-wall carbon nanotube in the gap of scanning tunneling microscope

J. Yamashita, H. Hirayama, Y. Ohshima, and K. Takayanagi

Appl. Phys. Lett. 74, 2450 (1999); http://dx.doi.org/10.1063/1.123877 (3 pages) | Cited 13 times

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Single-wall carbon nanotubes (SWNTs) were grown in the tunneling gap of a scanning tunneling microscope (STM). We could observe their growth processes in situ by operating the STM in a transmission electron microscope. The STM tip and sample were covered by graphite layers. The tip was lightly touched to the sample and subsequently retracted. Occasionally, a carbon nanobridge was generated between the tip and the sample. The bridge had the shape of SWNT at the tip side. © 1999 American Institute of Physics.
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61.48.-c Structure of fullerenes and related hollow and planar molecular structures
81.05.ub Fullerenes and related materials
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

Oxide damage by ion implantation in silicon

A. Losavio, B. Crivelli, F. Cazzaniga, M. Martini, G. Spinolo, and A. Vedda

Appl. Phys. Lett. 74, 2453 (1999); http://dx.doi.org/10.1063/1.123878 (3 pages) | Cited 5 times

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A significant increase in the etching rate of 680 nm thermally grown silicon dioxide layers has been observed following high energy ion implantation. Phosphorous and boron implantations have been considered, and the dependence upon fluence (from 1012 to 1014 atom/cm2)and ion energy (from 700 to 3000 keV) has been investigated. The effect of ion implantation has also been analyzed by thermally stimulated luminescence measurements above room temperature, to obtain complementary information on the physical mechanisms involved in the damage process. Data related to thermal annealing of oxide damage are also presented, indicating that a monotonic recovery takes place at temperatures higher than 550 °C although residual damage is observed even after thermal treatment up to 1000 °C. © 1999 American Institute of Physics.
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85.40.Ry Impurity doping, diffusion and ion implantation technology
61.82.Fk Semiconductors
61.80.Jh Ion radiation effects
61.72.uf Ge and Si

Optical investigations of AlGaN on GaN epitaxial films

G. Steude, B. K. Meyer, A. Göldner, A. Hoffmann, F. Bertram, J. Christen, H. Amano, and I. Akasaki

Appl. Phys. Lett. 74, 2456 (1999); http://dx.doi.org/10.1063/1.123879 (3 pages) | Cited 48 times

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We investigated coherently strained AlxGa1−xN/GaN heterostructures (0<x<0.22) grown by metalorganic vapor phase epitaxy on sapphire with photoluminescence (PL), reflexion and cathodoluminescence experiments. The energetic positions of the free A exciton as a function of the alloy compositions are deduced from temperature dependent PL and from reflexion measurements. We obtain a small bowing parameter and no evidence for a Stokes shift between absorption and emission. Compositional inhomogeneities are present, but the fluctuations are too small to be important for carrier localization. The broadening of the luminescence linewidth in the alloys can be described by statistical disorder of a random alloy. © 1999 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
78.60.Hk Cathodoluminescence, ionoluminescence
78.40.Fy Semiconductors
71.35.Cc Intrinsic properties of excitons; optical absorption spectra
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Electroluminescence and carrier transport of SiO2 film containing different density of Ge nanocrystals

Jia-Yu Zhang, Yong-Hong Ye, and Xi-Lin Tan

Appl. Phys. Lett. 74, 2459 (1999); http://dx.doi.org/10.1063/1.123880 (3 pages) | Cited 9 times

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Luminescent SiO2 films containing Ge nanocrystals (nc-Ge) are synthesized by implanting Ge ions into SiO2 films thermally grown on crystalline silicon, and the nc-Ge density was controlled by Ge+ implantation doses. The current–voltage measurements of their metal–oxide–semiconductor structures illustrate that the density and the distribution of nc-Ge have significant effects on their electroluminescence and carrier transport. The temperature-dependent current behavior is weaker in the films with low density, but stronger in the films with high density. Electroluminescent spectra indicate that high electric field can be established only in the films with low density. © 1999 American Institute of Physics.
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78.60.Fi Electroluminescence
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
61.72.up Other materials
78.66.-w Optical properties of specific thin films

Time-resolved reflectivity characterization of polycrystalline low-temperature-grown GaAs

Jean-François Roux, Jean-Louis Coutaz, and Arunas Krotkus

Appl. Phys. Lett. 74, 2462 (1999); http://dx.doi.org/10.1063/1.123881 (3 pages) | Cited 11 times

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Using femtosecond time resolved reflectivity, we have characterized the dynamics of photoinduced generated carriers in a polycrystalline low-temperature-grown GaAs sample. Our measurements are fitted with an analytical expression reliable for low pump power experiments. The sample, which presents no As precipitates, shows an ultrafast subpicosecond response together with a longer picosecond tail that we attribute to the midgap defect states. Moreover, we have observed the influence of surface roughness on the differential reflected signal. © 1999 American Institute of Physics.
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78.47.-p Spectroscopy of solid state dynamics
71.55.Eq III-V semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)

Cubic GaN formation under nitrogen-deficient conditions

S. Oktyabrsky, K. Dovidenko, A. K. Sharma, J. Narayan, and V. Joshkin

Appl. Phys. Lett. 74, 2465 (1999); http://dx.doi.org/10.1063/1.123882 (3 pages) | Cited 4 times

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We have studied crystal structure and associated defects in GaN/α-Al2O3 (0001) films grown under nitrogen-deficient conditions by metalorganic chemical vapor deposition and pulsed laser deposition. N-deficient films exhibit polycrystalline structure with a mixture of cubic zinc-blende and wurtzite hexagonal GaN grains retaining tetragonal bonding across the boundaries and hence the epitaxial orientations and polarity. Renucleation of the wurtzite phase at different {111} planes of cubic GaN results in a rough and faceted surface of the film. We elucidate that the cubic phase is more stable under the nitrogen deficiency. © 1999 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.-a Thin film structure and morphology
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Fg Pulsed laser ablation deposition
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Two-step preparation of 6H–SiC(0001) surface for epitaxial growth of GaN thin film

Qizhen Xue, Q. K. Xue, Y. Hasegawa, I. S. T. Tsong, and T. Sakurai

Appl. Phys. Lett. 74, 2468 (1999); http://dx.doi.org/10.1063/1.123883 (3 pages) | Cited 29 times

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A scratch-free and atomically flat 6H–SiC(0001) surface has been successfully prepared by a two-step method which combines atmospheric hydrogen treatment and ultrahigh vacuum Si etching. On this surface, a high-quality GaN(0001) thin film is obtained by radio frequency nitrogen plasma assisted molecular beam epitaxy. Its surface exhibits a typical terrace-plus-step morphology, which enables us to study various GaN(0001) surface superstructures and hollow-core defects with atomic resolution by scanning tunneling microscopy. © 1999 American Institute of Physics.
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81.65.Cf Surface cleaning, etching, patterning
81.05.Hd Other semiconductors
81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Growth and study of self-organized Ge quantum wires on Si(111) substrates

G. Jin, Y. S. Tang, J. L. Liu, and K. L. Wang

Appl. Phys. Lett. 74, 2471 (1999); http://dx.doi.org/10.1063/1.123884 (3 pages) | Cited 22 times

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Self-organized Ge quantum wires were grown on regular atomic steps formed along [110] direction on Si(111) substrates by annealing at 870 °C in vacuum. The samples were then studied by atomic force microscopy, polarization-dependent Raman scattering, and low temperature photoluminescence spectroscopy. The results suggest that good quality Ge quantum wires were formed and clear quantum confinement-induced quantization in the wires was observed. © 1999 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.66.Db Elemental semiconductors and insulators
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Cy Elemental semiconductors
78.55.Ap Elemental semiconductors
78.30.Am Elemental semiconductors and insulators
61.72.Cc Kinetics of defect formation and annealing

Exciton-phonon scattering in GaAs/AlAs quantum wires

A. Venu Gopal, Rajesh Kumar, A. S. Vengurlekar, T. Mélin, F. Laruelle, and B. Etienne

Appl. Phys. Lett. 74, 2474 (1999); http://dx.doi.org/10.1063/1.123012 (3 pages) | Cited 7 times

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We perform temperature-dependent photoluminescence measurements on a GaAs/AlAs quantum wire array (QWR-A) with a very low disorder. Using these, we deduce the temperature dependence of the homogeneous linewidth of the quasi-one-dimensional exciton to show that exciton scattering rates with optical phonons are enhanced in the QWR-A in comparison with a reference quantum well. © 1999 American Institute of Physics.
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71.35.Gg Exciton-mediated interactions
63.20.kk Phonon interactions with other quasiparticles
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Electrical properties of Ta2O5 thin films deposited on Ta

S. Ezhilvalavan and Tseung-Yuen Tseng

Appl. Phys. Lett. 74, 2477 (1999); http://dx.doi.org/10.1063/1.123013 (3 pages) | Cited 12 times

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The electrical properties of reactively sputtered Ta2O5 thin films with Ta as the bottom electrodes were investigated. Ta films were deposited onto SiO2/n-Si substrates by sputtering in Ar and in situ annealed at 700 °C for 10 min in N2 at a chamber pressure of 20 mTorr. We compared the effectiveness of both as-deposited and annealed Ta bottom electrodes on the leakage characteristics of Ta2O5 thin films. We also envisaged the influence of the surface roughness and morphology of the Ta bottom electrode in modifying the resultant microstructure of the annealed Ta2O5 films. Present studies demonstrate the use of Ta as a potential bottom electrode material to replace the precious metal electrodes and to simplify the fabrication process of the Ta2O5 storage capacitor. © 1999 American Institute of Physics.
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73.61.Ng Insulators
68.35.B- Structure of clean surfaces (and surface reconstruction)
73.40.Ns Metal-nonmetal contacts
84.32.Tt Capacitors
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