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23 Feb 2004

Volume 84, Issue 8, pp. 1233-1426

Issue Cover Spotlight Figure

Appl. Phys. Lett. 84, 1416 (2004); http://dx.doi.org/10.1063/1.1650904 (3 pages)

A. V. Krasavin and N. I. Zheludev
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Fast-response and scattering-free polymer network liquid crystals for infrared light modulators

Yun-Hsing Fan, Yi-Hsin Lin, Hongwen Ren, Sebastian Gauza, and Shin-Tson Wu

Appl. Phys. Lett. 84, 1233 (2004); http://dx.doi.org/10.1063/1.1649816 (3 pages) | Cited 33 times

Online Publication Date: 18 February 2004

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A fast-response and scattering-free homogeneously aligned polymer network liquid crystal (PNLC) light modulator is demonstrated at λ=1.55 μm wavelength. Light scattering in the near-infrared region is suppressed by optimizing the polymer concentration such that the network domain sizes are smaller than the wavelength. The strong polymer network anchoring assists LC to relax back quickly as the electric field is removed. As a result, the PNLC response time is ∼250× faster than that of the E44 LC mixture except that the threshold voltage is increased by ∼25×. © 2004 American Institute of Physics.
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42.70.Df Liquid crystals
42.79.Hp Optical processors, correlators, and modulators
42.25.Fx Diffraction and scattering

A pressure-tuned blue-violet InGaN/GaN laser diode grown on bulk GaN crystal

T. Suski, G. Franssen, P. Perlin, R. Bohdan, A. Bercha, P. Adamiec, F. Dybala, W. Trzeciakowski, P. Prystawko, M. Leszczyński, I. Grzegory, and S. Porowski

Appl. Phys. Lett. 84, 1236 (2004); http://dx.doi.org/10.1063/1.1649801 (3 pages) | Cited 15 times

Online Publication Date: 18 February 2004

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We demonstrate efficient wavelength tuning by means of hydrostatic pressure of an InGaN/GaN laser diode grown on bulk GaN crystal. Energy shifts of the emitted light with pressure have been found to be about 36 meV/GPa, which are high magnitudes for nitride-based device structures. This result is interpreted as being indicative of efficient screening of built-in electric fields in the studied device. Furthermore, the threshold current of the laser diode was found to be independent of applied pressure. The high magnitude of the pressure coefficient allowed for the achievement of a laser tuning range of up to 10 nm in the blue/violet region, using compact pressure equipment. © 2004 American Institute of Physics.
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81.05.Ea III-V semiconductors
42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
62.50.-p High-pressure effects in solids and liquids
42.60.Fc Modulation, tuning, and mode locking

Band spectroscopy of colloidal photonic crystal films

H. Míguez, V. Kitaev, and G. A. Ozin

Appl. Phys. Lett. 84, 1239 (2004); http://dx.doi.org/10.1063/1.1644913 (3 pages) | Cited 40 times

Online Publication Date: 18 February 2004

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Here we report on the optical properties associated with photonic bands of three-dimensional photonic colloidal crystals. Optical spectroscopy analysis shows fluctuations of the transmitted and reflected light intensity in photon frequency regions where no stop bands open up. The different optical features observed at low and high photon energy ranges are analyzed in terms of the band structure of the crystal. A relationship is found between dispersion of the bands and the features observed experimentally. On these premises, we show it is possible to map the higher-energy band region along nonprincipal directions of the first Brillouin zone by transmission spectroscopy. © 2004 American Institute of Physics.
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82.70.Dd Colloids
42.70.Qs Photonic bandgap materials
78.66.Nk Insulators

Strain-tunable silicon photonic band gap microcavities in optical waveguides

Chee Wei Wong, Peter T. Rakich, Steven G. Johnson, Minghao Qi, Henry I. Smith, Erich P. Ippen, Lionel C. Kimerling, Yongbae Jeon, George Barbastathis, and Sang-Gook Kim

Appl. Phys. Lett. 84, 1242 (2004); http://dx.doi.org/10.1063/1.1649803 (3 pages) | Cited 31 times

Online Publication Date: 18 February 2004

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See Also: Publisher's Note

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We report the design, device fabrication, and measurements of tunable silicon photonic band gap microcavities in optical waveguides, using direct application of piezoelectric-induced strain to the photonic crystal. We show, through first-order perturbation computations and experimental measurements, a 1.54 nm shift in cavity resonances at 1.56 μm wavelengths for an applied strain of 0.04%. The strain is applied through integrated piezoelectric microactuators. For operation at infrared wavelengths, we combine x-ray and electron-beam lithography with thin-film piezoelectric processing. This level of integration permits realizable silicon-based photonic chip devices, such as high-density optical filters, with active reconfiguration. © 2004 American Institute of Physics.
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81.05.Cy Elemental semiconductors
42.79.Gn Optical waveguides and couplers
42.70.Qs Photonic bandgap materials
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
42.79.Ci Filters, zone plates, and polarizers
42.82.Cr Fabrication techniques; lithography, pattern transfer
85.40.Hp Lithography, masks and pattern transfer

Enhancement of visible second-harmonic generation in epitaxial GaN-based two-dimensional photonic crystal structures

Gabriele Vecchi, Jérémi Torres, Dominique Coquillat, Marine Le Vassor d’Yerville, and Andrea Marco Malvezzi

Appl. Phys. Lett. 84, 1245 (2004); http://dx.doi.org/10.1063/1.1649800 (3 pages) | Cited 20 times

Online Publication Date: 18 February 2004

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Second-harmonic (SH) radiation generated in reflection is measured from the surface of a two-dimensional triangular photonic crystal in a GaN layer. A very large SH enhancement is observed when the incident radiation is resonant with a leaky photonic mode. The potential of second-harmonic generation as a tool for photonic band mapping is also envisaged. The extended transparency window of III-nitride wide band gap semiconductors coupled with large nonlinearities is an appealing feature pointing toward light control and manipulation in photonic structures. © 2004 American Institute of Physics.
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42.79.Nv Optical frequency converters
42.70.Qs Photonic bandgap materials
78.66.Fd III-V semiconductors

High quantum efficiency AlGaN solar-blind p-i-n photodiodes

R. McClintock, A. Yasan, K. Mayes, D. Shiell, S. R. Darvish, P. Kung, and M. Razeghi

Appl. Phys. Lett. 84, 1248 (2004); http://dx.doi.org/10.1063/1.1650550 (3 pages) | Cited 33 times

Online Publication Date: 18 February 2004

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We report AlGaN-based back-illuminated solar-blind ultraviolet p-i-n photodetectors with a peak responsivity of 136 mA/W at 282 nm without bias. This corresponds to a high external quantum efficiency of 60%, which improves to a value as high as 72% under 5 V reverse bias. We attribute the high performance of these devices to the use of a very-high quality AlN and Al0.87Ga0.13N/AlN superlattice material and a highly conductive Si–In co-doped Al0.5Ga0.5N layer. © 2004 American Institute of Physics.
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85.60.Dw Photodiodes; phototransistors; photoresistors
85.60.Gz Photodetectors (including infrared and CCD detectors)

Influence of mounting on continuous-wave photoluminescence from midinfrared PbSrSe/PbSe multiple quantum wells

F. Zhao, X. Lv, A. Majumdar, and Z. Shi

Appl. Phys. Lett. 84, 1251 (2004); http://dx.doi.org/10.1063/1.1650543 (3 pages) | Cited 5 times

Online Publication Date: 18 February 2004

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Strong continuous-wave photoluminescence from midinfrared lead–salt PbSrSe/PbSe multiple quantum wells grown on (111) BaF2 substrates by molecular-beam epitaxy was observed at temperatures from 100 to 300 K. The maximum output power was 2.9 and 0.6 mW at room temperature with episide down and episide up mounting, respectively. At 225 K, the temperature difference between the active region and the heat sink was about 32 °C for episide down mounting and 75 °C for episide up mounting. The peak energies shifted toward high energy with increasing temperature. The temperature-tuning coefficient obtained from episide down and episide up mounting was 0.45 and 0.50 meV/K. © 2004 American Institute of Physics.
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78.55.Et II-VI semiconductors
78.67.De Quantum wells
81.07.St Quantum wells
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.65.Fg Quantum wells

Impedance of photonic crystals and photonic crystal waveguides

R. Biswas, Z. Y. Li, and K. M. Ho

Appl. Phys. Lett. 84, 1254 (2004); http://dx.doi.org/10.1063/1.1649815 (3 pages) | Cited 24 times

Online Publication Date: 18 February 2004

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We develop and demonstrate the concept of impedance for a photonic crystal by generalizing the transverse wave impedance of conventional waveguides. The impedance involves a ratio of transverse fields and power flux. The calculated impedance for a two-dimensional photonic crystal is very well defined using the transfer matrix method. The predicted frequency-dependent reflectance from this impedance agrees very well with rigorous transfer matrix calculations for band modes and waveguiding modes in the band gap. This impedance concept will be very powerful in minimization of insertion loss into photonic crystal waveguides, designing waveguide splitters, and for modeling reflectance/transmittance from photonic crystals. © 2004 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.79.Gn Optical waveguides and couplers
42.25.Gy Edge and boundary effects; reflection and refraction

Imaging scanning tunneling microscope-induced electroluminescence in plasmonic corrals

Shunji Egusa, Yish-Hann Liau, and Norbert F. Scherer

Appl. Phys. Lett. 84, 1257 (2004); http://dx.doi.org/10.1063/1.1649799 (3 pages) | Cited 5 times

Online Publication Date: 18 February 2004

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An approach to image localized and propagating surface plasmon (SP) modes is introduced. It is shown that scanning tunneling microscope (STM)-electroluminescence, the radiative decay of SPs induced by inelastically tunneling electrons, observed in Fourier space yields distinct features that reflect the degree of delocalization and spatial distribution of SP modes. The propagating SP is isolated from the localized mode by way of this Fourier space imaging approach. Furthermore, a cylindrically symmetric spatial interference pattern is obtained when the STM-induced plasmon is created within a circular “corral” boundary condition. © 2004 American Institute of Physics.
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78.60.Fi Electroluminescence
73.22.Lp Collective excitations
63.20.Pw Localized modes
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Photon antibunching at high temperature from a single InGaAs/GaAs quantum dot

Richard P. Mirin

Appl. Phys. Lett. 84, 1260 (2004); http://dx.doi.org/10.1063/1.1650032 (3 pages) | Cited 19 times

Online Publication Date: 18 February 2004

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We report the observation of photon antibunching from a single, self-assembled InGaAs/GaAs quantum dot at temperatures up to 135 K. The second-order intensity correlation, g(2)(0), is measured to be less than 0.260 for temperatures up to 100 K. At 120 K, g(2)(0) increases to about 0.471, which is slightly less than the second-order intensity correlation expected from two independent single emitters. At 135 K, g(2)(0) is 0.667, which still indicates nonclassical light emission that is equivalent to having three independent single emitters.
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42.50.Dv Quantum state engineering and measurements
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
78.67.Hc Quantum dots

Development of high-operating-temperature infrared detectors with gold-doped Hg0.70Cd0.30Te

H. D. Shih, M. A. Kinch, F. Aqariden, P. K. Liao, P. D. Dreiske, M. J. Ohlson, T. W. Orent, J. E. Robinson, H. F. Schaake, T. H. Teherani, A. H. Kalma, and F. M. Roush

Appl. Phys. Lett. 84, 1263 (2004); http://dx.doi.org/10.1063/1.1650042 (3 pages) | Cited 2 times

Online Publication Date: 18 February 2004

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Excellent high-operating-temperature infrared photodiodes in the medium-wavelength infrared spectral band with cutoff wavelengths ∼ 5 μm at 77 K were fabricated on Hg1−xCdxTe samples (x ∼ 0.30) prepared by liquid-phase epitaxy in a tellurium-melt reactor. The samples were doped with indium to ∼ 1×1014 cm−3 and gold to ∼ 5×1015 cm−3. Thick planar diodes ( ∼ 80 μm thick) and thin cylindrical diodes ( ∼ 10 μm thick) of the n-on-p type were fabricated, and they gave comparable, excellent detector dark values within a factor of two. At 130 K, dark currents as low as 5×10−7 A/cm2 were obtained. © 2004 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.60.Dw Photodiodes; phototransistors; photoresistors
73.50.Pz Photoconduction and photovoltaic effects
72.40.+w Photoconduction and photovoltaic effects

Terahertz quantum-cascade lasers based on an interlaced photon-phonon cascade

Rüdeger Köhler, Alessandro Tredicucci, Cosimo Mauro, Fabio Beltram, Harvey E. Beere, Edmund H. Linfield, A. Giles Davies, and David A. Ritchie

Appl. Phys. Lett. 84, 1266 (2004); http://dx.doi.org/10.1063/1.1650905 (3 pages) | Cited 21 times

Online Publication Date: 18 February 2004

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A THz (λ ∼ 80 μm) quantum-cascade laser utilizing alternating photon- and phonon-emitting stages has been developed to achieve efficient extraction of electrons from the lower laser level. Thermal backfilling of electrons is drastically reduced leading to an operation up to 95 K and a weak temperature dependence of the power versus current slope efficiency. The threshold current density is 280 A cm−2 at 6 K and increases to 580 A cm−2 at 90 K. Peak output powers of 10 mW at 30 K and 4 mW at 80 K are obtained. © 2004 American Institute of Physics.
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42.60.By Design of specific laser systems
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
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Mechanism for small electron current fraction in a vacuum arc cathode spot on a refractory cathode

I. I. Beilis

Appl. Phys. Lett. 84, 1269 (2004); http://dx.doi.org/10.1063/1.1647272 (3 pages) | Cited 4 times

Online Publication Date: 18 February 2004

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A mechanism for refractory cathode spot operation in a vacuum arc is proposed, based on the presence of a finite electric field Ep at the cathode sheath–plasma interface. The proposed model determines the relationship between the electron current and the total spot current density j and includes a system of equations solved for cathode plasma containing a mixture of ion states. The calculation shows that Ep reaches a value, ∼ 106 V/cm, and j is 104–108 A/cm2, when the electron current fraction s increases from 0.5 to 0.9. It is discovered that for a refractory cathode, ions with high ionicity (from 2 to 4) can be generated in the spot region for a relatively small s, 0.7–0.9, in contrast to ionization in the plasma jet, as predicted previously for copper cathodes. © 2004 American Institute of Physics.
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52.80.Vp Discharge in vacuum
52.75.-d Plasma devices
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Control of polytype formation in silicon carbide heteroepitaxial films by pulsed-laser deposition

Takeshi Kusumori, Hachizo Muto, and Manuel E. Brito

Appl. Phys. Lett. 84, 1272 (2004); http://dx.doi.org/10.1063/1.1649797 (3 pages) | Cited 6 times

Online Publication Date: 18 February 2004

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Control of silicon carbide (SiC) polytype formation has been achieved. 3C, 2H, and 4H SiC heteroepitaxial films are fabricated on a sapphire (0001) substrate at a low temperature of 1100 °C using a pulsed-laser deposition (PLD) method. Images made by transmission electron microscopy clearly show that each film consists of a single polytype. The polytype of the SiC films can be changed by varying just two easily controlled parameters: the laser pulse frequency and the substrate temperature. These results suggest that precise control of growth conditions, which is essential for polymorphic materials, is possible using the PLD method. © 2004 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Fg Pulsed laser ablation deposition
68.55.A- Nucleation and growth

Stress-strain characteristics in Ni–Ga–Fe ferromagnetic shape memory alloys

Y. Sutou, N. Kamiya, T. Omori, R. Kainuma, K. Ishida, and K. Oikawa

Appl. Phys. Lett. 84, 1275 (2004); http://dx.doi.org/10.1063/1.1642277 (3 pages) | Cited 52 times

Online Publication Date: 18 February 2004

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Tensile and compressive stress–strain characteristics for Ni–Ga–Fe ferromagnetic shape memory alloys at several temperatures were investigated by mechanical test and a critical stress versus temperature diagram was obtained. The crystal structure of the martensite phase obtained by tensile-stress-induced martensitic transformation was estimated from the degree of the transformation strain. Stress-induced martensite transformed from the parent phase with an L21 structure showed a 14M structure by tensile stress and by further applying stress, the 14M structure martensitically was transformed into an L10 structure. Moreover, it was found in the compressive test that variant rearrangement occurred by very low compressive stress less than 3 MPa, which is similar to the phenomenon seen in Ni–Mn–Ga alloys. © 2004 American Institute of Physics.
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62.20.F- Deformation and plasticity
81.30.Kf Martensitic transformations
62.20.D- Elasticity

Influence of particle oxide coating on light scattering by submicron metal particles on silicon wafers

Jung Hyeun Kim, Sheryl H. Ehrman, and Thomas A. Germer

Appl. Phys. Lett. 84, 1278 (2004); http://dx.doi.org/10.1063/1.1650555 (3 pages) | Cited 15 times

Online Publication Date: 18 February 2004

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We report the effect of room-temperature oxidation on scattering of 633 nm light by copper particles deposited on a silicon wafer. The results provide a validation for a theory of light scattering by coated particles on a substrate and establish the lifetime of these particles as light scattering standards to be on the order of a few months. The results also suggest that the room-temperature oxidation of copper particles proceeds in a continuous manner, rather than approaching an asymptotic thickness as found by Cabrera and Mott [Rep. Prog. Phys. 12, 163 (1948)] on copper films. © 2004 American Institute of Physics.
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78.66.Nk Insulators
81.15.Rs Spray coating techniques
81.65.Mq Oxidation
68.37.Lp Transmission electron microscopy (TEM)

Microstructural evolution of a-plane GaN grown on a-plane SiC by metalorganic chemical vapor deposition

M. D. Craven, F. Wu, A. Chakraborty, B. Imer, U. K. Mishra, S. P. DenBaars, and J. S. Speck

Appl. Phys. Lett. 84, 1281 (2004); http://dx.doi.org/10.1063/1.1650545 (3 pages) | Cited 63 times

Online Publication Date: 18 February 2004

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This letter describes the relationship between the morphological evolution of heteroepitaxial a-plane GaN films and the formation of the extended defect structure. The initial a-plane GaN growth on a-plane SiC substrates (via a high temperature AlN buffer layer) follows a Volmer–Weber growth mode. Consequently, the coalescence of three-dimensional (3D) islands generates threading dislocations which dominate the nonpolar GaN film’s microstructure (3×1010 cm−2). Exposed nitrogen-face surfaces, identified using x-ray diffraction measurements and convergent beam electron diffraction analysis, are present throughout the 3D growth and are the likely source of basal plane faulting (7×105 cm−1) within the film. Atomic force microscopy and scanning electron microscopy were used to image the morphological transition, which was correlated to changes in the a-GaN crystal tilt mosaic measured by x-ray rocking curves. © 2004 American Institute of Physics.
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68.55.A- Nucleation and growth
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.Nn Stacking faults and other planar or extended defects
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Ps Atomic force microscopy (AFM)

Band-gap renormalization in highly excited GaN

Takehiko Nagai, Takeshi J. Inagaki, and Yoshihiko Kanemitsu

Appl. Phys. Lett. 84, 1284 (2004); http://dx.doi.org/10.1063/1.1650552 (3 pages) | Cited 16 times

Online Publication Date: 18 February 2004

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We have studied the band-gap renormalization in highly excited GaN thin films by means of photoluminescence (PL) spectral measurements from 6 to 300 K. The renormalized band-gap energy is determined from the low-energy edge of the broad PL band due to the high-density electron and hole (e–h) plasmas. The reduction of the band-gap energy depends on the density of e–h plasmas, but is independent of temperature. The renormalized band-gap energy is calculated using two theoretical models. Our results suggest that the e–h pair correlation plays an essential role in highly excited GaN. © 2004 American Institute of Physics.
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78.55.Cr III-V semiconductors
71.20.Nr Semiconductor compounds
73.50.Mx High-frequency effects; plasma effects
78.66.Fd III-V semiconductors

Enhanced formation of luminescent nanocrystal Si embedded in Si/SiO2 superlattice by excimer laser irradiation

Daigil Cha, Jung H. Shin, In-Hyuk Song, and Min-Koo Han

Appl. Phys. Lett. 84, 1287 (2004); http://dx.doi.org/10.1063/1.1650037 (3 pages) | Cited 5 times

Online Publication Date: 18 February 2004

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The effect of excimer laser annealing on the formation of luminescent nanocrystal Si (nc-Si) embedded in Si/SiO2 superlattice is investigated. An amorphous Si/SiO2 superlattice consisting of 20 periods of 2 nm thin Si layers and 5 nm thin SiO2 layers was deposited on Si using electron cyclotron resonance plasma-enhanced chemical vapor deposition. Excimer laser annealing alone did not result in any nc-Si luminescence even at an energy density sufficient to melt the Si layers. However, if the nc-Si is preformed by a thermal anneal, subsequent excimer laser annealing will result in a threefold increase of the nc-Si luminescence intensity. The temperature dependence of the nc-Si luminescence spectrum, lifetime, and intensity indicates that excimer laser annealing activates luminescent nc-Si by removing defects and amorphous regions in thermally crystallized Si layers without significant changes in the size or shape of nc-Si. © 2004 American Institute of Physics.
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78.55.Hx Other solid inorganic materials
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
81.05.Hd Other semiconductors
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology

Analytical solution of the almost-perfect-lens problem

R. Merlin

Appl. Phys. Lett. 84, 1290 (2004); http://dx.doi.org/10.1063/1.1650548 (3 pages) | Cited 81 times

Online Publication Date: 18 February 2004

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See Also: Erratum

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The problem of imaging for a slab of a lossless left-handed material with refractive index n = −(1−σ)1/2 is solved analytically for ∣σ∣≪1. The electromagnetic field behavior is determined largely by singularities arising from the excitation of surface polaritons with wave vector q→±∞. Depending on the sign of σ, the near-field is either odd or even with respect to the lens middle plane. Consistent with other nonanalytical studies, the resolution depends logarithmically on ∣σ∣. With minor alterations, these results apply as well to the electrostatic limit. © 2004 American Institute of Physics.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Photoluminescence and Raman scattering in three-dimensional Si/Si1−xGex nanostructures

B. V. Kamenev, L. Tsybeskov, J.-M. Baribeau, and D. J. Lockwood

Appl. Phys. Lett. 84, 1293 (2004); http://dx.doi.org/10.1063/1.1650873 (3 pages) | Cited 21 times

Online Publication Date: 18 February 2004

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We report detailed Raman and photoluminescence (PL) measurements in Si/Si1−xGex nanostructures grown by molecular-beam epitaxy under conditions of near Stranski–Krastanov (S-K) growth mode. In a series of samples with x controllably increased from 0.098 to 0.53, we observe that an increase in Raman signal related to Ge–Ge vibrations clearly correlates with (i) a redshift in the PL peak position, (ii) an increase in the activation energy of PL thermal quenching, and (iii) an increase in the PL quantum efficiency. The results indicate that in S-K Si/Si1−xGex nanostructures with x>0.5 Ge atoms form nanometer-sized clusters with a nearly pure Ge core and a SiGe shell. © 2004 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
68.65.Fg Quantum wells
78.67.De Quantum wells
81.40.Gh Other heat and thermomechanical treatments
78.30.Am Elemental semiconductors and insulators
78.55.Ap Elemental semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Luminescence enhancement in Eu3+-doped α- and γ-Al2O3 produced by pressure-assisted low-temperature combustion synthesis

O. Ozuna, G. A. Hirata, and J. McKittrick

Appl. Phys. Lett. 84, 1296 (2004); http://dx.doi.org/10.1063/1.1650908 (3 pages) | Cited 15 times

Online Publication Date: 18 February 2004

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Intense red luminescence in Eu3+-doped gamma (γ) and alpha (α) alumina (Al2O3) phosphors obtained by direct and indirect combustion synthesis at low-temperatures is reported. γ and α-(Al1−xEux)2O3 are easily produced by combustion synthesis at 280 °C in the range of x = 0.001–0.06 at. %. The well-defined direct synthesis allows europium ions to incorporate into the α or γ alumina lattice in spite of the large size difference between these ions and the aluminum cations in Al2O3. These materials yield a strong fluorescence at room temperature due to f–f transition lines within Eu3+ (4f6) electron emission configuration. Furthermore, from luminescence measurements, it is deduced that Eu3+ occupy low-symmetry sites in the Al2O3 lattice. © 2004 American Institute of Physics.
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78.60.Hk Cathodoluminescence, ionoluminescence
78.55.Hx Other solid inorganic materials
81.05.Cy Elemental semiconductors
61.72.S- Impurities in crystals

Observation of spontaneous ordering in the optoelectronic material GaInNP

Y. K. Su, C. H. Wu, S. H. Hsu, S. J. Chang, W. C. Chen, Y. S. Huang, and H. P. Hsu

Appl. Phys. Lett. 84, 1299 (2004); http://dx.doi.org/10.1063/1.1650045 (3 pages) | Cited 7 times

Online Publication Date: 18 February 2004

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We report a detailed structural and optical characterization of high-quality GaInNP films. These films were grown by gas-source molecular-beam epitaxy on GaAs (100) substrates. These epitaxial layers were then characterized by a high-resolution x-ray rocking curve (HRXRC) and photoluminescence (PL) measurements. With nitrogen incorporation, the PL peak redshifts, indicating bandgap reduction and the line-width broadening increases due to alloy scattering. The anisotropic properties of the polarized HRXRC and polarized piezoreflectance spectra are used to prove the spontaneous ordering in GaInP incorporating nitrogen. Furthermore, ordering-induced superlattice-like microstructure shown in high-resolution transmission electron microscope images is used to confirm the spontaneous ordering in Ga0.44In0.56NxP1−x epitaxial layers. © 2004 American Institute of Physics.
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68.55.-a Thin film structure and morphology
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
78.20.hb Piezo-optical, elasto-optical, acousto-optical, and photoelastic effects
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
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Surface photovoltage effects on the isomeric semiconductors of boron-carbide

A. N. Caruso, Snjezana Balaz, Bo Xu, P. A. Dowben, A. S. McMullen-Gunn, J. I. Brand, Y. B. Losovyj, and D. N. McIlroy

Appl. Phys. Lett. 84, 1302 (2004); http://dx.doi.org/10.1063/1.1648136 (3 pages) | Cited 11 times

Online Publication Date: 18 February 2004

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During exposure to synchrotron radiation, closo 1,7-dicarbadodecaborane (metacarborane) and closo 1,2-dicarbadodecaborane (orthocarborane) decompose, and are accompanied by increasingly evident photoemission surface photovoltage effects. We show that metacarborane and orthocarborane form self-doped n-type and p-type boron-carbides, respectively. Surface photovoltage effects dominate the photoemission final state, not the changes in electronic structure due to decomposition. © 2004 American Institute of Physics.
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72.40.+w Photoconduction and photovoltaic effects
79.60.Bm Clean metal, semiconductor, and insulator surfaces
71.20.Ps Other inorganic compounds
64.75.-g Phase equilibria

Chemical structure of the interface in ultrathin HfO2/Si films

Jong-Cheol Lee, S.-J. Oh, Moonju Cho, Cheol Seong Hwang, and Ranju Jung

Appl. Phys. Lett. 84, 1305 (2004); http://dx.doi.org/10.1063/1.1645984 (3 pages) | Cited 51 times

Online Publication Date: 18 February 2004

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The chemical states of the HfO2/Si (100) interface were investigated using transmission electron microscopy and high-resolution x-ray photoelectron spectroscopy. The depth distributions of Hf chemical states showed that the Hf 4f binding energy remains unchanged with the depth and there is no signature of more than one Hf-O state. These facts strongly suggest that the chemical state of the interfacial layer is not Hf-silicate, as previously believed. Instead, the compositions are mainly Si2O3 and SiO2, judging from the deconvolution of Si 2p spectra. The dielectric constant κ=4.8 of the interfacial layer is also consistent with the above conclusions. © 2004 American Institute of Physics.
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68.35.Ct Interface structure and roughness
68.37.Lp Transmission electron microscopy (TEM)
61.50.Lt Crystal binding; cohesive energy
73.20.At Surface states, band structure, electron density of states
77.22.Ch Permittivity (dielectric function)
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
79.60.Jv Interfaces; heterostructures; nanostructures
77.55.-g Dielectric thin films
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