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18 Nov 2002

Volume 81, Issue 21, pp. 3915-4082

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Creating large bandwidth line defects by embedding dielectric waveguides into photonic crystal slabs

Wah Tung Lau and Shanhui Fan

Appl. Phys. Lett. 81, 3915 (2002); http://dx.doi.org/10.1063/1.1523637 (3 pages) | Cited 27 times

Online Publication Date: 12 November 2002

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We introduce a general designing procedure that allows us, for any given photonic crystal slab, to create an appropriate line defect structure that possesses single-mode bands with large bandwidth and low dispersion within the photonic band-gap region below the light line. This procedure involves designing a high index dielectric waveguide that is phase matched with the gap of the photonic crystal slab, and embedding the dielectric waveguide as a line defect into a crystal in a specific configuration that is free of edge states within the guiding bandwidth. As an example, we show a single mode line defect waveguide with a bandwidth approaching 13% of the center-band frequency, and with a linear dispersion relation throughout most of the bandwidth. © 2002 American Institute of Physics.
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42.82.Et Waveguides, couplers, and arrays
42.79.Gn Optical waveguides and couplers
42.70.Qs Photonic bandgap materials

Detection of thermal acoustic radiation from laser-heated deep tissue

Eugene V. Krotov, Maxim V. Zhadobov, Alexander M. Reyman, Grigory P. Volkov, and Vladimir P. Zharov

Appl. Phys. Lett. 81, 3918 (2002); http://dx.doi.org/10.1063/1.1521245 (3 pages) | Cited 9 times

Online Publication Date: 12 November 2002

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A multichannel acoustic antenna with a linear piezoelectric transducer array was developed to detect thermal acoustic radiation from a deep-lying sample zone heated by laser. A cw Nd:YAG laser (wavelength, 1064 nm; power, 1 W) was used as the thermal source. An optical fiber was inserted into the sample (beef liver) to deliver laser radiation into the deep zone and to heat the area around the fiber tip through absorption. The experiments demonstrated the capability of a new device for real-time monitoring of internal temperature at depths up to 3.5 cm with a spatial resolution of about 5 mm and a sensitivity of about 0.5 K. It is shown that experimental data can be used to visualize heat diffusion effects in deep-lying zones and the spatial position of the fiber tip, and to quantitatively estimate thermal diffusivity and acoustic and optical absorption coefficients. In addition to its laser applications, the described technique could be a promising tool for monitoring temperature distribution at the deposition of an alternative external energy (microwave, focused ultrasound, etc.) in deep-lying tissues. © 2002 American Institute of Physics.
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87.63.D- Ultrasonography
42.62.Be Biological and medical applications
87.19.Pp Biothermics and thermal processes in biology
43.80.Vj Acoustical medical instrumentation and measurement techniques
87.63.L- Visual imaging
43.38.Fx Piezoelectric and ferroelectric transducers
07.60.Vg Fiber-optic instruments
87.50.W- Optical/infrared radiation effects
43.38.Hz Transducer arrays, acoustic interaction effects in arrays

High-efficiency top-emitting organic light-emitting devices

M.-H. Lu, M. S. Weaver, T. X. Zhou, M. Rothman, R. C. Kwong, M. Hack, and J. J. Brown

Appl. Phys. Lett. 81, 3921 (2002); http://dx.doi.org/10.1063/1.1523150 (3 pages) | Cited 96 times

Online Publication Date: 12 November 2002

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Based on theoretical arguments that top-emitting organic light-emitting devices (TOLEDs) can be more efficient than equivalent bottom-emitting devices, we fabricated TOLEDs comprising reflective anodes and transparent compound cathodes that emit 20.8% more photons in the forward 120° cone than equivalent bottom-emitting OLEDs. Device optimization by tuning the thickness of the top indium–tin–oxide layer according to a microcavity model is also reported. © 2002 American Institute of Physics.
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85.60.Jb Light-emitting devices
78.66.Li Other semiconductors
78.66.Qn Polymers; organic compounds

Energy transfer from organics to rare-earth complexes

María A. Díaz-García, Susana Fernández De Ávila, and Mark G. Kuzyk

Appl. Phys. Lett. 81, 3924 (2002); http://dx.doi.org/10.1063/1.1520338 (3 pages) | Cited 12 times

Online Publication Date: 12 November 2002

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Energy transfer from several semiconducting organic molecules and polymers to rareearth complexes in the form of spin-cast films is reported. Energy transfer is observed in poly(N-vinylcarbazole) (PVK) films doped with various europium and samarium complexes. Polystyrene films containing the hole-transporting organic molecule 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD) and the electron-transporting molecule N,N′-bis(3-methylphenyl)-N,N-diphenylbenzidine also show energy transfer to the europium complexes, but not to the samarium ones. We show that energy transfer from PBD to the europium complexes is more efficient than from PVK. These films are semiconducting and easy to process, so they are candidates for monochromatic light-emitting diodes. © 2002 American Institute of Physics.
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78.55.Kz Solid organic materials
78.66.Qn Polymers; organic compounds

Separation of photonic crystal waveguides modes using femtosecond time-of-flight

M. C. Netti, C. E. Finlayson, J. J. Baumberg, M. D. B. Charlton, M. E. Zoorob, J. S. Wilkinson, and G. J. Parker

Appl. Phys. Lett. 81, 3927 (2002); http://dx.doi.org/10.1063/1.1520709 (3 pages) | Cited 17 times

Online Publication Date: 12 November 2002

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We demonstrate that ultrabroadband ultrashort-pulse white light supercontinua can be used to track the group velocity of photons in optical waveguides using a Kerr gate technique. Results on silicon nitride slab waveguides show both polarization birefringence and multimode dispersion, which vanish at critical wavelengths. When photonic crystals are embedded in the waveguides, the higher order modes are excited within the band-gap region, demonstrating the need to control their dispersion to make effective use of photonic crystal waveguide devices. © 2002 American Institute of Physics.
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42.82.Et Waveguides, couplers, and arrays
42.70.Qs Photonic bandgap materials
42.65.Wi Nonlinear waveguides
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

All-solid-state electrochromic device composed of WO3 and Ni(OH)2 with a Ta2O5 protective layer

Kwang-Soon Ahn, Yoon-Chae Nah, Yung-Eun Sung, Ki-Yun Cho, Seung-Shik Shin, and Jung-Ki Park

Appl. Phys. Lett. 81, 3930 (2002); http://dx.doi.org/10.1063/1.1522478 (3 pages) | Cited 20 times

Online Publication Date: 12 November 2002

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An all-solid-state electrochromic device composed of WO3 and Ni(OH)2 with a Ta2O5 protective layer was prepared by rf magnetron sputtering and lamination with a proton-conducting solid polymer electrolyte. This device had good durability, high transmittance modulation (18%–74%) and coloration efficiency (about 84 cm2 C−1), and good response times (8.5 and 18 s, respectively, during the bleaching and coloring processes). This indicates that Ta2O5 layers are electrochemically stable and can be used as protective layer for Ni(OH)2 as well as WO3. © 2002 American Institute of Physics.
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85.60.Pg Display systems
78.20.Jq Electro-optical effects
82.35.Rs Polyelectrolytes

Robustness to optical feedback of oxide-confined versus proton-implanted vertical-cavity surface-emitting lasers

P. A. Judge, C. H. L. Quay, and J. A. Hudgings

Appl. Phys. Lett. 81, 3933 (2002); http://dx.doi.org/10.1063/1.1523159 (3 pages) | Cited 2 times

Online Publication Date: 12 November 2002

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We show that the coupling efficiency of optical feedback into a single-mode oxide-confined vertical-cavity surface-emitting laser (VCSEL) is half that of a similar proton-implanted VCSEL, so the oxide-confined devices are less sensitive to feedback-induced variations in threshold current and lasing wavelength. However, strong optical feedback causes coherence collapse in both types of lasers and can also result in satellite modes and coherence length discontinuities in oxide-confined VCSELs. While polarized feedback tends to suppress polarization-switching in oxide-confined devices, the opposite effect is observed in proton-implanted VCSELs. © 2002 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
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Mechanism for cathode spot grouping in vacuum arcs

I. I. Beilis

Appl. Phys. Lett. 81, 3936 (2002); http://dx.doi.org/10.1063/1.1523158 (3 pages) | Cited 2 times

Online Publication Date: 12 November 2002

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A model of cathode spot grouping observed when the vacuum arc runs in a transverse magnetic field is proposed. The current per group spot is calculated considering the relation between the plasma kinetic pressure and magnetic pressure in the acceleration region of current carried cathode plasma jet. The calculated currents per group spot increase linearly with the magnetic field and this dependence agrees well with previous measurements. © 2002 American Institute of Physics.
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52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.80.Vp Discharge in vacuum
52.25.-b Plasma properties
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Reflectance difference spectroscopy of an ultrathin indium arsenide layer on indium phosphide (001)

C. H. Li, Y. Sun, S. B. Visbeck, D. C. Law, and R. F. Hicks

Appl. Phys. Lett. 81, 3939 (2002); http://dx.doi.org/10.1063/1.1523650 (3 pages) | Cited 4 times

Online Publication Date: 12 November 2002

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A model system has been created which allows the surface and bulk contributions to the reflectance difference spectrum to be distinguished. In particular, an indium arsenide film, less than 10 Å thick, has been grown on indium phosphide (001). Reflectance difference spectra of the InAs/InP surfaces were collected and compared to those of InP and InAs. It was found that the InAs/InP heterostructures exhibited electronic transitions between surface states characteristic of InAs (001), while retaining the surface-perturbed bulk transitions characteristic of InP (001). Furthermore, the optical anisotropy arising from the arsenic dimer bonds was shifted 0.2 eV higher for InAs/InP compared to that for InAs. This shift is proportional to 1/a2, where a is the bulk lattice constant. © 2002 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.40.Fy Semiconductors
73.20.At Surface states, band structure, electron density of states
81.05.Ea III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Origins of field enhancement in electron field emission from ion beam synthesized SiC layers

W. M. Tsang, S. P. Wong, and J. K. N. Lindner

Appl. Phys. Lett. 81, 3942 (2002); http://dx.doi.org/10.1063/1.1520715 (3 pages) | Cited 10 times

Online Publication Date: 12 November 2002

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SiC layers were synthesized by high-dose carbon implantation into silicon. Their electron field emission properties were studied and correlated with results from atomic force microscopy (AFM) and conducting AFM measurements. It is clearly demonstrated that there are two types of field enhancement mechanisms responsible for the improvement of the electron field emission properties of these ion beam synthesized SiC layers. In the as-implanted samples, the local field enhancement effect is attributed to electrical inhomogeneity due to the existence of small conducting graphitic clusters embedded in the layer. On the other hand, in the annealed samples, the dominant field enhancement mechanism is attributed to a surface morphology effect due to the formation of small protrusion structures at the surface. © 2002 American Institute of Physics.
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79.70.+q Field emission, ionization, evaporation, and desorption
61.72.uf Ge and Si
61.72.Cc Kinetics of defect formation and annealing

Photoexcitation-electron-paramagnetic-resonance studies of the carbon vacancy in 4H-SiC

N. T. Son, B. Magnusson, and E. Janzén

Appl. Phys. Lett. 81, 3945 (2002); http://dx.doi.org/10.1063/1.1522822 (3 pages) | Cited 27 times

Online Publication Date: 12 November 2002

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Photoexcitation-electron-paramagnetic-resonance (photo-EPR) studies were performed on p-type 4H-SiC irradiated with 2.5 MeV electrons. At W-band frequencies (∼95 GHz) different EPR spectra could be well separated, allowing a reliable determination of the ground state levels of the associated defects. The photo-EPR results obtained for the positively charged carbon vacancy (VC+) can be explained by a deep donor model with the (+/0) level located at (1.47±0.06) eV above the valence band. © 2002 American Institute of Physics.
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76.30.Mi Color centers and other defects
61.72.J- Point defects and defect clusters
71.55.Ht Other nonmetals
61.82.Fk Semiconductors
61.80.Fe Electron and positron radiation effects

Visible emission from N-rich turbostratic boron nitride thin films doped with Eu, Tb, and Tm

Q. L. Liu, F. F. Xu, and T. Tanaka

Appl. Phys. Lett. 81, 3948 (2002); http://dx.doi.org/10.1063/1.1524037 (3 pages) | Cited 12 times

Online Publication Date: 12 November 2002

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Red, green, and blue light emissions have been obtained at 80 and 300 K by cathodoluminescence (CL) from N-rich turbostratic BN thin films doped with Eu, Tb, and Tm, respectively. The films were grown by rf magnetron sputtering in an atmosphere of Ar and NH3 gas mixture using EuB6, TbB6, and TmB12 targets, respectively. Infrared absorption measurements, transmission electron microscopy, and electron probe microanalysis show that the matrix of the films is N-rich turbostratic BN. The sharp characteristic emission lines corresponding to Eu3+, Tb3+, and Tm3+ intra-4fn shell transitions are resolved in the CL spectral range from 350 to 800 nm at 80 and 300 K. © 2002 American Institute of Physics.
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78.60.Hk Cathodoluminescence, ionoluminescence
78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
68.37.Lp Transmission electron microscopy (TEM)

Fast Q-tensor method for modeling liquid crystal director configurations with defects

Gi-Dong Lee, James Anderson, and Philip J. Bos

Appl. Phys. Lett. 81, 3951 (2002); http://dx.doi.org/10.1063/1.1523157 (3 pages) | Cited 13 times

Online Publication Date: 12 November 2002

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A fast Q-tensor method, which can model the configuration of the liquid crystal director fields containing defects, is proposed. Conceptually based on the Oseen–Frank approach, we have added temperature energy density terms in addition to the strain energy term. We have also derived an improved normalization method for fast calculations. The method is used to model the conversion of a reverse tilt wall to a pair of disclination lines. © 2002 American Institute of Physics.
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61.30.Cz Molecular and microscopic models and theories of liquid crystal structure
61.30.Jf Defects in liquid crystals

Optical anisotropy of self-assembled InGaAs quantum dots embedded in wall-shaped and air-bridge structures

T. Nakaoka, S. Kako, S. Ishida, M. Nishioka, and Y. Arakawa

Appl. Phys. Lett. 81, 3954 (2002); http://dx.doi.org/10.1063/1.1522824 (3 pages) | Cited 5 times

Online Publication Date: 12 November 2002

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Strain effect on optical anisotropy of quantum dots has been investigated by changing the surrounding matrix of the dots. Optical anisotropy can be induced by lateral patterning of the matrix of the dots, although such anisotropy is absent in the as-grown dots. A reduction of the optical anisotropy is observed by changing the laterally patterned structure into a free-standing structure or an air bridge. The optical anisotropy is mainly attributed to strain asymmetry in the fabricated structures. The presence of the strain asymmetry is confirmed by the observation of a doublet fine structure in spectrally resolved photoluminescence of single quantum dots. © 2002 American Institute of Physics.
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78.67.Hc Quantum dots
78.66.Fd III-V semiconductors
68.65.Hb Quantum dots (patterned in quantum wells)
71.70.Fk Strain-induced splitting
81.07.Ta Quantum dots
81.16.Dn Self-assembly
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances

Computational design of a material for high-efficiency spin-polarized electron source

A. Janotti and Su-Huai Wei

Appl. Phys. Lett. 81, 3957 (2002); http://dx.doi.org/10.1063/1.1521510 (3 pages) | Cited 9 times

Online Publication Date: 12 November 2002

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The search for the highest quality and efficient spin-polarized electron source (SPES) is of fundamental importance in the investigation of spin-dependent phenomena in atomic, condensed-matter, nuclear, and particle physics. We propose a material, AgGaSe2 in the CuAu phase, as a high-quality SPES. We show that AgGaSe2 in the CuAu phase has an “ideal” band structure that allows the generation of electron beams with 100% polarization: a direct band gap with large and positive spin-orbit splitting and crystal-field splitting. Moreover, we predict that strain-free AgGaSe2 in CuAu phase can be obtained by epitaxial growth on ZnSe substrate. © 2002 American Institute of Physics.
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71.20.Nr Semiconductor compounds
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
71.70.Ch Crystal and ligand fields

Growth mode and strain evolution during InN growth on GaN(0001) by molecular-beam epitaxy

Y. F. Ng, Y. G. Cao, M. H. Xie, X. L. Wang, and S. Y. Tong

Appl. Phys. Lett. 81, 3960 (2002); http://dx.doi.org/10.1063/1.1523638 (3 pages) | Cited 48 times

Online Publication Date: 12 November 2002

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Epitaxial growth of InN on GaN(0001) by plasma-assisted molecular-beam epitaxy is investigated over a range of growth parameters including source flux and substrate temperature. Combining reflection high-energy electron diffraction (RHEED) and scanning tunneling microscopy (STM), we establish a relationship between film growth mode and the deposition condition. Both two-dimensional (2D) and three-dimensional (3D) growth modes of the film are observed. For 2D growth, sustained RHEED intensity oscillations are recorded while STM reveals 2D nucleation islands. For 3D growth, less than three oscillation periods are observed indicating the Stranski–Krastanov (SK) growth mode of the film. Simultaneous measurements of (reciprocal) lattice constant by RHEED suggest a gradual relaxation of the strain in film, which commences during the first bilayer (BL) deposition and almost completes after 2–4 BLs. For SK growth, 3D islanding initiates after the strain has mostly been relieved, presumably by dislocations, so the islands are likely strain free. © 2002 American Institute of Physics.
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68.55.A- Nucleation and growth
68.60.Bs Mechanical and acoustical properties
81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)

Adhesion force of polymeric three-dimensional microstructures fabricated by microstereolithography

Dongmin Wu, Nicholas Fang, Cheng Sun, and Xiang Zhang

Appl. Phys. Lett. 81, 3963 (2002); http://dx.doi.org/10.1063/1.1522825 (3 pages) | Cited 6 times

Online Publication Date: 12 November 2002

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The adhesion between microstructures represents a great challenge in reliability of polymeric three-dimensional structures fabricated by microstereolithography (μSL). During the evaporative releasing, the capillary force of the solvent causes the deformation and adhesion of the fabricated beams. We present a method to determine the adhesion force of polymeric microstructures fabricated by μSL. The test structures with parallel beams were fabricated and released from the liquid resin via evaporation. By measuring the relationship between the adhesion length and the geometry of the beams, the adhesion force between two 1,6-hexanediol diacrylate (HDDA) polymeric parallel beams is determined as γ = 72±5 mN/m. This simple method and the determined adhesion force provide a key in designing reliable polymeric microelectromechanical systems in preventing the stiction problem. © 2002 American Institute of Physics.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
68.35.Np Adhesion
85.40.Hp Lithography, masks and pattern transfer
62.20.F- Deformation and plasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations

Nanothermodynamic analysis of surface effect on expansion characteristics of Ga in carbon nanotubes

Yihua Gao and Yoshio Bando

Appl. Phys. Lett. 81, 3966 (2002); http://dx.doi.org/10.1063/1.1524038 (3 pages) | Cited 18 times

Online Publication Date: 12 November 2002

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Thermodynamic analysis was performed with respect to the effect of surface tension on the expansion characteristics of a one-dimensional nanoscale liquid Ga column inside a carbon nanotube. The analysis showed that the surface tension affects the column inner pressure, and that the smaller the column diameter, the greater the surface effect. Based on the analysis, it is quantitatively explained why a liquid Ga column with 75 nm diameter has virtually the same expansion coefficient as that of Ga in a macroscopic state in the range of 50 to 500 °C, and suggested that the volumetric expansion coefficient can be directly used for the calibration of a given nanothermometer with a diameter larger than 10 nm. © 2002 American Institute of Physics.
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65.20.-w Thermal properties of liquids
68.03.Cd Surface tension and related phenomena
61.46.-w Structure of nanoscale materials
07.20.Dt Thermometers

Linear and nonlinear optical properties of Ag nanocluster/BaTiO3 composite films

Guang Yang, Weitian Wang, Yueliang Zhou, Huibin Lu, Guozhen Yang, and Zhenghao Chen

Appl. Phys. Lett. 81, 3969 (2002); http://dx.doi.org/10.1063/1.1522832 (3 pages) | Cited 38 times

Online Publication Date: 12 November 2002

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To investigate the optical properties of metallic nanocluster/oxide composite films, Ag nanocluster/BaTiO3 composite films were synthesized on MgO (100) substrates by co-depositing the Ag and BaTiO3 targets using pulsed laser deposition. The x-ray diffraction results demonstrated that the Ag and BaTiO3 were well crystallized. The x-ray photoelectron spectroscopy analysis indicated that the samples were composed of nano-metal Ag embedded in the BaTiO3 matrices. The optical absorption properties were measured from 300 to 800 nm, and the absorption peaks due to the surface plasmon resonance of Ag particles were observed. With increasing the Ag concentration, the peak absorption increased and shifted to longer wavelength (redshift). Furthermore, the z-scan results showed that the films exhibited large optical nonlinearities and the signs of the nonlinear absorption (β) and nonlinear refractive index (n2) changed with increasing the Ag concentration. © 2002 American Institute of Physics.
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78.66.Vs Fine-particle systems
78.66.Sq Composite materials
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Origin and consequences of a high stacking fault density in epitaxial ZnO layers

D. Gerthsen, D. Litvinov, Th. Gruber, C. Kirchner, and A. Waag

Appl. Phys. Lett. 81, 3972 (2002); http://dx.doi.org/10.1063/1.1523151 (3 pages) | Cited 35 times

Online Publication Date: 12 November 2002

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Transmission electron microscopy was applied to study ZnO grown by metalorganic vapor phase epitaxy on Al2O3(0001) substrates. The defect structure of the material is dominated by an extraordinary high density of small stacking faults with extensions between 5 and 25 nm which induce a bright small-scale speckle contrast under weak-beam imaging conditions. The stacking faults are terminated by Frank partial dislocations with Burgers vectors of the type 1/6 〈2math03〉. The precipitation of interstitial atoms is the most likely process for the generation of the stacking faults, which are characterized by an additional (0002) plane. The high stacking fault density can be considered as an indicator for high point defect concentrations, which are expected to aggravate the control of the electrical conductivity. © 2002 American Institute of Physics.
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72.80.Ey III-V and II-VI semiconductors

Ultrashort hole capture time in Mg-doped GaN thin films

Kung-Hsuan Lin, Gia-Wei Chern, Shi-Wei Chu, Chi-Kuang Sun, Huili Xing, Yulia Smorchkova, Stacia Keller, Umesh Mishra, and Steven P. DenBaars

Appl. Phys. Lett. 81, 3975 (2002); http://dx.doi.org/10.1063/1.1522827 (3 pages) | Cited 5 times

Online Publication Date: 12 November 2002

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Hole capture time in p-type GaN was measured by using a femtosecond pump-probe technique. The capture time constant that holes are trapped by Mg-related states was found to be shorter than 10 ps. The hole capture time increases with decreased hole excess energy. By comparing two samples with different doping concentrations, it was found that the hole capture time also decreases with increased doping concentrations. © 2002 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
71.55.Eq III-V semiconductors
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
78.47.-p Spectroscopy of solid state dynamics

Formation of epitaxial Au/Ni/Au ohmic contacts to p-GaN

J. Narayan, H. Wang, T.-H. Oh, H. K. Choi, and J. C. C. Fan

Appl. Phys. Lett. 81, 3978 (2002); http://dx.doi.org/10.1063/1.1524032 (3 pages) | Cited 24 times

Online Publication Date: 12 November 2002

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We have designed a promising contact scheme to p-GaN, where Au/Ni/Au layers are deposited on p-GaN and annealed in air for 30 min at 470 °C to produce low-resistivity ohmic contacts. The Au layer in contact with p-GaN grows epitaxially via domain matching epitaxy, which acts as a template for NiO growth via lattice matching epitaxy. The 〈111〉 oriented gold rotates 30° in the basal (0001) plane of GaN by 30° with the following orientation relationship: [111]Au//[0001]GaN; [11math]Au//[2mathmath0]GaN. As a result, we can create epitaxial NiO–Au composite, where Au as well as NiO are in contact with p-GaN. This epitaxial composite structure is envisaged to be important in achieving low-resistivity ohmic contacts in p-GaN. We present the details of atomic structure, epitaxial relationship, chemistry, and electrical properties of ohmic contacts. © 2002 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
73.40.Cg Contact resistance, contact potential
68.35.Ct Interface structure and roughness
68.55.A- Nucleation and growth
81.40.Gh Other heat and thermomechanical treatments
68.55.-a Thin film structure and morphology

Scanning photoelectron microscopy study of laser-induced surface reactions in Pt/Si(001)

A. J. Nelson, M. Danailov, A. Barinov, B. Kaulich, L. Gregoratti, and M. Kiskinova

Appl. Phys. Lett. 81, 3981 (2002); http://dx.doi.org/10.1063/1.1522480 (3 pages) | Cited 3 times

Online Publication Date: 12 November 2002

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Synchrotron radiation scanning photoemission spectroscopy has been used to study thin platinum silicide layers produced by pulsed-laser annealing of vacuum deposited Pt films on Si(001). High-resolution photoemission measurements on the Pt 4f and Si 2p core lines were used to evaluate morphological changes and interfacial reactions. Distinct regions were identified with varying PtSi thickness and mixed Pt-rich silicides. The lateral distribution and the chemical phases formed within the laser-irradiated spots indicate that the local laser-induced temperature rise controls the interfacial processes. © 2002 American Institute of Physics.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.37.Xy Scanning Auger microscopy, photoelectron microscopy
79.20.Ds Laser-beam impact phenomena

Temperature dependence of the GaNxP1−x band gap and effect of band crossover

G. Yu. Rudko, I. A. Buyanova, W. M. Chen, H. P. Xin, and C. W. Tu

Appl. Phys. Lett. 81, 3984 (2002); http://dx.doi.org/10.1063/1.1522496 (3 pages) | Cited 21 times

Online Publication Date: 12 November 2002

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The absorption edge of GaNxP1−x alloys (0.01 ⩽ x ⩽ 0.03) is shown to exhibit a direct-band gap-like behavior. Thermal variation of the band gap energy Eg, however, is found to be the same or even smaller than that for the indirect band gap of GaP and depends on the N content. The effect is tentatively attributed to the following counteracting contributions to the band edge formation. An interaction with N-related localized states, especially significant in the vicinity of band crossover (e.g., x = 0.013), causes a substantial slow down of the Eg shift with temperature. On the contrary, an increasing contribution of Γc states, which becomes predominant for the higher compositions, leads to the larger thermal variation in Eg. © 2002 American Institute of Physics.
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71.20.Nr Semiconductor compounds
78.40.Fy Semiconductors

Ga(As,N) layers in the dilute N limit studied by depth-resolved capacitance spectroscopy

P. Krispin, V. Gambin, J. S. Harris, and K. H. Ploog

Appl. Phys. Lett. 81, 3987 (2002); http://dx.doi.org/10.1063/1.1522823 (3 pages) | Cited 5 times

Online Publication Date: 12 November 2002

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Deep carrier traps in the upper half of the band gap of Ga(As,N) layers in the dilute N limit (⩽0.1%) are examined by depth-resolved capacitance spectroscopy on n-type Ga(As,N)/GaAs heterojunctions grown by molecular-beam epitaxy. Distinct compositional fluctuations are revealed in the deep-level spectra. Native point defects are predominantly formed in regions with larger N content. High concentrations of electron traps near the surface control the properties of as-grown Ga(As,N) layers and lead to strong carrier depletion and frequency- as well as temperature-dependent capacitance (admittance dispersion). The related defects at the surface can be removed by rapid thermal annealing. © 2002 American Institute of Physics.
Show PACS
73.20.Hb Impurity and defect levels; energy states of adsorbed species
71.55.Eq III-V semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
68.35.Dv Composition, segregation; defects and impurities
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