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8 Oct 2007

Volume 91, Issue 15, Articles (15xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 91, 153101 (2007); http://dx.doi.org/10.1063/1.2793688 (3 pages)

B. J. Lee, K. Park, and Z. M. Zhang
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Two-dimensional polymer photonic crystal band-edge lasers fabricated by nanoimprint lithography

V. Reboud, P. Lovera, N. Kehagias, M. Zelsmann, C. Schuster, F. Reuther, G. Gruetzner, G. Redmond, and C. M. Sotomayor Torres

Appl. Phys. Lett. 91, 151101 (2007); http://dx.doi.org/10.1063/1.2798250 (3 pages) | Cited 21 times

Online Publication Date: 8 October 2007

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We report on the fabrication and characterization of two-dimensional polymer photonic crystal band-edge lasers operating in the visible range. The components have been fabricated in a dye chromophore-loaded polymer matrix by nanoimprint lithography. High-symmetry band-edge modes are used to generate laser emission. The experimental lasing frequencies are in good agreement with those calculated using a two-dimensional plane wave algorithm. These results demonstrate the potential of nanoimprint lithography for the fabrication of two-dimensional planar photonic crystal structures in an active medium in a one-step process.
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42.55.Tv Photonic crystal lasers and coherent effects
42.82.Cr Fabrication techniques; lithography, pattern transfer

Midinfrared lead-chalcogenide vertical external cavity surface emitting laser with 5 μm wavelength

M. Rahim, M. Arnold, F. Felder, K. Behfar, and H. Zogg

Appl. Phys. Lett. 91, 151102 (2007); http://dx.doi.org/10.1063/1.2798254 (3 pages) | Cited 14 times

Online Publication Date: 8 October 2007

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Midinfrared vertical external cavity surface emitting lasers for 5 μm wavelength have been realized. The active parts consist either of a 2 μm thick PbTe gain layer or of two 150 nm PbTe layers embedded in Pb1−xEuxTe barriers, and an epitaxial two pair Pb1−yEuyTe/BaF2 Bragg mirror. They are optically pumped with a 1.5 μm laser. No precautions for efficient heat removal were implemented. The two-layer structure emits 1–2 mW continuous wave at 95 K with threshold pump power as low as ∼ 300 mW. In pulsed mode, peak powers are >50 mW, and lasing occurs up to ∼ 140 K.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Highly directional radiation pattern of microdisk cavities

E. Peter, A. Dousse, P. Voisin, A. Lemaître, D. Martrou, A. Cavanna, J. Bloch, and P. Senellart

Appl. Phys. Lett. 91, 151103 (2007); http://dx.doi.org/10.1063/1.2789956 (3 pages) | Cited 5 times

Online Publication Date: 8 October 2007

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The far field radiation pattern of microdisk cavities embedding a quantum well is measured through angle resolved microphotoluminescence. The radiation pattern presents two narrow lobes slightly off the disk plane, in apparent contradiction with previous theoretical predictions. The observed radiation pattern is shown to result from interferences with light reflected by the sample substrate. It can be fully reproduced given the microdisk precise geometry as well as the whispering gallery mode azimuthal number.
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78.67.De Quantum wells
78.55.-m Photoluminescence, properties and materials
42.79.-e Optical elements, devices, and systems

Relaxation of transport properties in electron-doped SrTiO3

Moty Schultz and Lior Klein

Appl. Phys. Lett. 91, 151104 (2007); http://dx.doi.org/10.1063/1.2795336 (3 pages) | Cited 7 times

Online Publication Date: 9 October 2007

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See Also: Publisher's Note | RETRACTION

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We electron-dope single crystal samples of SrTiO3 by exposing them to Ar+ irradiation and observe carrier mobility similar in its magnitude and temperature dependence to the carrier mobility in other electron-doped SrTiO3 systems. We find that some transport properties are time dependent. In particular, the sheet resistance increases with time at a temperature-dependent rate, suggesting an activation barrier on the order of 1 eV. We attribute the relaxation effects to diffusion of oxygen vacancies—a process with energy barrier similar to the observed activation energy.
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72.20.Fr Low-field transport and mobility; piezoresistance
61.80.Jh Ion radiation effects
61.82.Ms Insulators
66.30.Lw Diffusion of other defects
61.72.J- Point defects and defect clusters

Nanocrystals in silicon photonic crystal standing-wave cavities as spin-photon phase gates for quantum information processing

Y.-F. Xiao, J. Gao, X. Yang, R. Bose, G.-C. Guo, and C. W. Wong

Appl. Phys. Lett. 91, 151105 (2007); http://dx.doi.org/10.1063/1.2795798 (3 pages) | Cited 9 times

Online Publication Date: 9 October 2007

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By virtue of a silicon high-Q photonic crystal nanocavity, we propose and examine theoretically interactions between a stationary electron spin qubit of a semiconductor nanocrystal and a flying photon qubit. Firstly, we introduce, derive, and demonstrate the explicit conditions toward realization of a spin-photon phase gate, and propose these interactions as a generalized quantum interface for quantum information processing. Secondly, we examine single-spin-induced reflections as direct evidence of intrinsic bare and dressed modes in our coupled nanocrystal-cavity system.
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42.70.Qs Photonic bandgap materials
42.50.-p Quantum optics

Bistability and nonlinear gain in 1.55 μm vertical cavity semiconductor optical amplifiers: Theory and experiments

Antonio Hurtado, Ian D. Henning, and Michael J. Adams

Appl. Phys. Lett. 91, 151106 (2007); http://dx.doi.org/10.1063/1.2798053 (3 pages) | Cited 8 times

Online Publication Date: 11 October 2007

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We report experimental measurements of power and wavelength optical bistability and nonlinear gain in two 1.55 μm vertical-cavity semiconductor optical amplifiers operated in reflection. Anticlockwise and clockwise nonlinear switching and bistability, both with high on-off contrast ratio up to 3.5:1, have been observed in the optical power and wavelength domains. Theoretical modeling gives excellent agreement with the experimental measurements.
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42.55.Px Semiconductor lasers; laser diodes
42.65.Pc Optical bistability, multistability, and switching, including local field effects

Intense 1540 nm emission from Er doped Ce:YAG phosphor

Jian Xin Meng, Kok Wai Cheah, Zhao Pu Shi, and Jin Qing Li

Appl. Phys. Lett. 91, 151107 (2007); http://dx.doi.org/10.1063/1.2785136 (3 pages) | Cited 16 times

Online Publication Date: 11 October 2007

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A very efficient energy transfer from Ce3+ to Er3+ in yttrium aluminum garnet (YAG) matrix is observed. The transfer gives about 1000 times enhancement to the Er3+ 1540 nm emission. This is due to efficient absorption by the allowed 4f-5d transition of Ce3+ ions then transfer to Er3+ ions via a matched energy level 4F9/2. Thus the 1540 nm emission was strongly sensitized by exciting an allowed transition in an inorganic matrix. In fact, the 1540 nm emission was further enhanced via the cross-relaxation process 2F5/2→2F7/2(Ce3+), 4I11/2→4I13/2(Er3+). The result means that a new class of material, Ce Er:YAG, was produced and it potentially can be an efficient near-IR emitter.
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78.55.Hx Other solid inorganic materials

Femtosecond laser-written quasi-phase-matched waveguides in lithium niobate

Jens Thomas, Matthias Heinrich, Jonas Burghoff, Stefan Nolte, Antonio Ancona, and Andreas Tünnermann

Appl. Phys. Lett. 91, 151108 (2007); http://dx.doi.org/10.1063/1.2799178 (3 pages) | Cited 25 times

Online Publication Date: 11 October 2007

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We report on thermally stable optical waveguides written in periodically poled lithium niobate with a femtosecond laser using a two line approach. Both fundamental and second harmonic light at 1064 and 532 nm are guided with low damping losses. In a 10-mm-long sample a conversion efficiency of 58% was achieved.
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42.79.Gn Optical waveguides and couplers
42.65.Wi Nonlinear waveguides

Enhanced transmission of periodic, quasiperiodic, and random nanoaperture arrays

Carsten Rockstuhl, Falk Lederer, Thomas Zentgraf, and Harald Giessen

Appl. Phys. Lett. 91, 151109 (2007); http://dx.doi.org/10.1063/1.2799240 (3 pages) | Cited 11 times

Online Publication Date: 12 October 2007

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We numerically and experimentally show that the enhanced transmission of an array of annular nanoapertures is independent of the nanoaperture’s arrangement. This holds if this enhancement primarily relies on Fabry-Pérot resonances of guided modes in the nanoapertures. We observe a comparable transmission spectrum for a periodic, a quasiperiodic, and even a random nanoaperture arrangement. This complements previous findings where the enhanced transmission of a circular nanoaperture array was shown to rely on the excitation of surface-plasmon polaritons at the metal surface and thus strongly depended on the nanoaperture’s arrangement.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
41.20.Jb Electromagnetic wave propagation; radiowave propagation
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Substrate heating influence on plume propagation during pulsed laser deposition of complex oxides

A. Sambri, S. Amoruso, X. Wang, M. Radovic’, F. Miletto Granozio, and R. Bruzzese

Appl. Phys. Lett. 91, 151501 (2007); http://dx.doi.org/10.1063/1.2795792 (3 pages) | Cited 16 times

Online Publication Date: 8 October 2007

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We investigate the effects of the substrate-heater temperature on the expansion dynamics of laser plumes of complex oxides in oxygen atmosphere. We observed a considerable reduction of the background gas resistance to plume propagation as the substrate temperature was increased, leading to a remarkable change in the velocity of the species impacting the substrate during film growth. The deposition temperature thus influences film growth not only through its direct thermal effect on surface kinetics of adatoms, but also by affecting the energetic properties of the precursors in the gas phase. We interpret the results with a simplified model of plume front propagation, accounting for the change in the background gas density induced by the substrate temperature.
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81.15.Fg Pulsed laser ablation deposition
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Comparative study of atmospheric pressure low and radio frequency microjet plasmas produced in a single electrode configuration

Dan Bee Kim, J. K. Rhee, B. Gweon, S. Y. Moon, and W. Choe

Appl. Phys. Lett. 91, 151502 (2007); http://dx.doi.org/10.1063/1.2794774 (3 pages) | Cited 34 times

Online Publication Date: 11 October 2007

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Microsize jet-type plasmas were generated in a single pin electrode structure source for two separate input frequencies of 50 kHz and 13.56 MHz in the ambient air. The copper pin electrode radius was 360 μm, and it was placed in a Pyrex tube with a radius of 3 mm for helium gas supply. Due to the input frequency difference, the generated plasmas showed distinct discharge characteristics for their plasma physical appearances, electrical properties, gas temperatures, and optical properties. Strengths and weaknesses of both plasmas were discussed for further applications.
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52.75.-d Plasma devices
52.50.Dg Plasma sources
52.80.-s Electric discharges
52.25.Fi Transport properties
52.25.Os Emission, absorption, and scattering of electromagnetic radiation

Suppression of suprathermal ions from a colloidal microjet target containing SnO2 nanoparticles by using double laser pulses

Takeshi Higashiguchi, Masanori Kaku, Masahito Katto, and Shoichi Kubodera

Appl. Phys. Lett. 91, 151503 (2007); http://dx.doi.org/10.1063/1.2799175 (3 pages) | Cited 7 times

Online Publication Date: 12 October 2007

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We have demonstrated suppression of suprathermal ions from a colloidal microjet target plasma containing tin-dioxide (SnO2) nanoparticles irradiated by double laser pulses. We observed a significant decrease of the tin and oxygen ion signals in the charged-state-separated energy spectra when double laser pulses were irradiated. The peak energy of the singly ionized tin ions decreased from 9 to 3 keV when a preplasma was produced. The decrease in the ion energy, considered as debris suppression, is attributed to the interaction between an expanding low-density preplasma and a main laser pulse.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.25.Jm Ionization of plasmas
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Mechanical deformation and failure of electrospun polyacrylonitrile nanofibers as a function of strain rate

Mohammad Naraghi, Ioannis Chasiotis, Harold Kahn, Yongkui Wen, and Yuris Dzenis

Appl. Phys. Lett. 91, 151901 (2007); http://dx.doi.org/10.1063/1.2795799 (3 pages) | Cited 15 times

Online Publication Date: 8 October 2007

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The mechanical deformation of 12 μm long electrospun polyacrylonitrile (PAN) nanofibers with diameters of 300–600 nm was investigated. The nanofibers were subjected to cold drawing in atmospheric conditions and at strain rates between 10−2 and 10−4 s−1. The ultimate strain of the PAN nanofibers was 60%–130% varying monotonically with the strain rate. On the contrary, the fiber tensile strength, ranging between 30 and 130 MPa, varied nonmonotonically with the slowest drawing rate resulting in the largest ductilities and fiber strengths. At the two faster rates, the large fiber ductilities originated in the formation of a cascade of ripples (necks), while at the slowest strain rate, the nanofibers deformed homogeneously allowing for the largest engineering strengths and extension ratios.
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62.20.F- Deformation and plasticity
81.40.Lm Deformation, plasticity, and creep
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
62.25.-g Mechanical properties of nanoscale systems
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Surface plasmon coupled fluorescence from copper substrates

Michael J. R. Previte, Yongxia Zhang, Kadir Aslan, and Chris D. Geddes

Appl. Phys. Lett. 91, 151902 (2007); http://dx.doi.org/10.1063/1.2794761 (3 pages) | Cited 4 times

Online Publication Date: 8 October 2007

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Previously, we reported the observation of metal enhanced emission from copper nanoparticles. In this letter, we report the observation of surface plasmon coupled fluorescence (SPCF) or emission from thin copper (Cu) continuous films. Using Fresnel calculations to theoretically calculate the reflectance curves for polymethyl methacrylate films doped with sulforhodamine 101, we correlated the minimum reflectance angles for both s- and p-polarized lights with maximum fluorescence emission. These observations reveal that we can achieve SPCF with copper substrates and possibly design inexpensive copper substrates for fluorescent sensing applications and potentially, fluorescent based electrical signals and circuits.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.55.Hx Other solid inorganic materials
68.55.-a Thin film structure and morphology

Epitaxial growth mechanisms of AlN on SiC substrates at room temperature

Myunghee Kim, Jitsuo Ohta, Atsushi Kobayashi, Hiroshi Fujioka, and Masaharu Oshima

Appl. Phys. Lett. 91, 151903 (2007); http://dx.doi.org/10.1063/1.2795804 (3 pages) | Cited 6 times

Online Publication Date: 9 October 2007

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Epitaxial AlN films have been grown on atomically flat 6H-SiC (0001) and 4H-SiC (0001) substrates at room temperature (RT), and their growth mechanisms have been investigated. It has been revealed that the growth of AlN at RT proceeds in a layer-by-layer mode from the initial stage. During the growth, AlN nucei have an equilateral triangular shape probably due to the anisotropy in growth rates. The triangular AlN nuclei at the adjacent terraces formed on the 6H-SiC substrates are rotated by 60°, whereas the triangular AlN nuclei on the 4H-SiC were formed in the same direction on all of the terraces. This phenomenon can be explained by the difference in the arrangement of the atoms for the topmost layers.
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68.55.-a Thin film structure and morphology

Photochromism in yttrium hydride

Ayako Ohmura, Akihiko Machida, Tetsu Watanuki, Katsutoshi Aoki, Satoshi Nakano, and K. Takemura

Appl. Phys. Lett. 91, 151904 (2007); http://dx.doi.org/10.1063/1.2794755 (3 pages) | Cited 2 times

Online Publication Date: 12 October 2007

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Transparent orange yttrium hydride turns to black when illuminated by visible laser light at pressures of several gigapascals at room temperature. The marked reduction in optical transmittance extends over the infrared region, suggesting that illumination creates persistent free carriers. The opaque black sample returns to the transparent orange hydride during room-temperature annealing for a few hours. Photochromism is pronounced for the coexistent state of the metallic fcc-YH2 and the insulating hexagonal-YH3 state but is depressed for the single phase of hexagonal-YH3. The results indicate that light illumination can modify the optical and possibly electronic properties during a certain period of times.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.40.Gh Other heat and thermomechanical treatments

Coherent anti-Stokes Raman scattering polarized microscopy of three-dimensional director structures in liquid crystals

A. V. Kachynski, A. N. Kuzmin, P. N. Prasad, and I. I. Smalyukh

Appl. Phys. Lett. 91, 151905 (2007); http://dx.doi.org/10.1063/1.2800887 (3 pages) | Cited 18 times

Online Publication Date: 12 October 2007

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We demonstrate three-dimensional vibrational imaging of director structures in liquid crystals using coherent anti-Stokes Raman scattering (CARS) polarized microscopy. Spatial mapping of the structures is based on sensitivity of a polarized CARS signal to the orientation of anisotropic molecules in liquid crystals. As an example, we study structures in a smectic material and demonstrate that single-scan CARS and two-photon fluorescence images of molecular orientation patterns are consistent with each other and with the structure model.
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61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures
61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order
63.50.-x Vibrational states in disordered systems
78.30.C- Liquids
78.55.Bq Liquids
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Dislocation reduction in gallium nitride films using scandium nitride interlayers

M. A. Moram, Y. Zhang, M. J. Kappers, Z. H. Barber, and C. J. Humphreys

Appl. Phys. Lett. 91, 152101 (2007); http://dx.doi.org/10.1063/1.2794009 (3 pages) | Cited 16 times

Online Publication Date: 8 October 2007

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We describe a method of reducing threading dislocation densities in 0001-oriented GaN from (5.0±0.5)×109 cm−2 to (3.1±0.4)×107 cm−2 (for coalesced films) or to below 5×106 cm−2 (for partially coalesced films) in a single step, without lithography. Lattice-matched, dislocation-blocking scandium nitride interlayers are deposited on a 500 nm GaN-on-sapphire template. Dislocation-free GaN islands grown on the ScN interlayer nucleate both on the interlayer and on tiny areas of the GaN template exposed through openings in the interlayer. However, some dislocations are generated above the interlayer during subsequent island coalescence.
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81.05.Ea III-V semiconductors
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.55.-a Thin film structure and morphology
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

N–O related shallow donors in silicon: Stoichiometry investigations

H. E. Wagner, H. Ch. Alt, W. von Ammon, F. Bittersberger, A. Huber, and L. Koester

Appl. Phys. Lett. 91, 152102 (2007); http://dx.doi.org/10.1063/1.2795801 (3 pages) | Cited 5 times

Online Publication Date: 8 October 2007

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For clarification of the unknown chemical composition of the electrically active N–O defects in silicon, an ingot with variable oxygen content and fixed nitrogen concentration was investigated by infrared spectroscopy. Shallow donor spectra taken at different sample positions, i.e., oxygen concentrations, show a strong oxygen influence on the absorption of the different N–O species, allowing determination of the number of oxygen atoms for each species via the corresponding mass-action law. From that, the energetically deepest defect N–O-5 is associated with a NO configuration, whereas the strongest complex N–O-3 has NO2 composition. Further members of the shallow donor family contain three oxygen atoms.
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81.05.Cy Elemental semiconductors
81.05.Bx Metals, semimetals, and alloys
61.72.-y Defects and impurities in crystals; microstructure
61.66.Bi Elemental solids
61.66.Dk Alloys
71.55.Cn Elemental semiconductors
78.30.Am Elemental semiconductors and insulators

Polarity-dependent reversible resistance switching in Ge–Sb–Te phase-change thin films

Ramanathaswamy Pandian, Bart J. Kooi, George Palasantzas, Jeff T. M. De Hosson, and Andrew Pauza

Appl. Phys. Lett. 91, 152103 (2007); http://dx.doi.org/10.1063/1.2798242 (3 pages) | Cited 15 times

Online Publication Date: 8 October 2007

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In this paper, we demonstrate reversible resistance switching in a capacitorlike cell using a Ge–Sb–Te film that does not rely on amorphous-crystalline phase change. The polarity of the applied electric field switches the cell resistance between lower- and higher-resistance states, as was observed in current-voltage characteristics. Moreover, voltage pulses less than 1.25 V showed this switching within time scales of microseconds with more than 40% contrast between the resistance states. The latter are found to be nonvolatile for months. The switching could also be achieved at nanoscales with atomic force microscopy with a better resistance contrast of three orders of magnitude.
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73.61.At Metal and metallic alloys

Charge-retraction time-of-flight measurement for organic charge transport materials

Jason U. Wallace, Ralph H. Young, Ching W. Tang, and Shaw H. Chen

Appl. Phys. Lett. 91, 152104 (2007); http://dx.doi.org/10.1063/1.2798592 (3 pages) | Cited 3 times

Online Publication Date: 8 October 2007

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This letter describes an all-electrical technique, charge-retraction time-of-flight (CR-TOF), to measure charge carrier mobility through an organic layer. Carriers are injected and accumulated at a blocking interface, then retracted. The retraction current transient is nearly indistinguishable from a traditional time-of-flight photocurrent. The CR-TOF technique is validated by measurement of the hole mobility of two well-known compounds, 4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine and 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl, utilizing 1,3,5-tris(N-phenylbenzimidazol-2-yl)-benzene as a hole-blocking layer. A sample layer thickness of less than 300 nm can be used for the measurement.
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72.20.Fr Low-field transport and mobility; piezoresistance
73.61.Ph Polymers; organic compounds

Strong dependence of transport properties of metal-semiconductor-metal graphene ribbons on their geometrical features

Antonis N. Andriotis, Ernst Richter, and Madhu Menon

Appl. Phys. Lett. 91, 152105 (2007); http://dx.doi.org/10.1063/1.2798593 (3 pages) | Cited 12 times

Online Publication Date: 8 October 2007

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The conducting properties of various finite graphene ribbons and their junctions are investigated. These were found to depend strongly on their size and geometric features. Small arm-chair ribbons, when connected through tapered geometries, are found to exhibit very narrow conducting windows. No conductance is found through small armchair zigzag armchair ribbon junctions when connected via pentagon-heptagon defect lines. However, the conducting windows become broader as the size of the ribbons increases.
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73.40.Sx Metal-semiconductor-metal structures
73.61.Wp Fullerenes and related materials

Band engineering in Al0.5Ga0.5N/GaN superlattice by modulating Mg dopant

Jinchai Li and Junyong Kang

Appl. Phys. Lett. 91, 152106 (2007); http://dx.doi.org/10.1063/1.2798589 (3 pages) | Cited 5 times

Online Publication Date: 10 October 2007

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The electronic structures of Mg modulation-doped and undoped Al0.5Ga0.5N/GaN superlattices (SLs) are investigated by using first-principles density function theory. The layer-projected densities of states indicate that the band alignment is changed from type I to type II and the band bending due to polarization is reduced significantly by modulating Mg dopant in AlGaN layer. It is further confirmed by the calculations of the partial charge density profiles and the valence band offsets where the valence-band maximum of AlGaN in Mg modulation-doped SL is located above that of GaN. The strong hybridization between N and Mg orbitals plays an important role on the upward shifts of the valence band edges.
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73.21.Cd Superlattices

The origin of electron injection improvement in organic light-emitting devices with an organic oxide/rubrene electron injection layer

Kwanghee Cho, Sang Wan Cho, Chung-Nam Whang, Kwangho Jeong, Seong Jun Kang, and Yeonjin Yi

Appl. Phys. Lett. 91, 152107 (2007); http://dx.doi.org/10.1063/1.2798588 (3 pages) | Cited 1 time

Online Publication Date: 11 October 2007

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The electronic structure of tris(8-hydroquinoline) aluminum (Alq3)/rubrene/poly(ethylene glycol) dimethyl ether (PEGDE)/Al interfaces was studied using in situ ultraviolet photoelectron spectroscopy (UPS) and x-ray photoelectron spectroscopy (XPS). The UPS and XPS spectra allowed us to evaluate the complete energy level diagrams and to analyze the chemical interactions at the interfaces. When a PEGDE/rubrene double layer was inserted between Al and Alq3, the electron injection barrier height was greatly reduced compared to the interface without PEGDE/rubrene or with a single insertion layer of either PEGDE or rubrene.
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85.60.Jb Light-emitting devices
79.60.Jv Interfaces; heterostructures; nanostructures
71.20.-b Electron density of states and band structure of crystalline solids

Determination of InN–GaN heterostructure band offsets from internal photoemission measurements

Zahid Hasan Mahmood, A. P. Shah, Abdul Kadir, M. R. Gokhale, Sandip Ghosh, Arnab Bhattacharya, and B. M. Arora

Appl. Phys. Lett. 91, 152108 (2007); http://dx.doi.org/10.1063/1.2794788 (3 pages) | Cited 8 times

Online Publication Date: 11 October 2007

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Band discontinuities at the InN–GaN heterointerface are experimentally determined from internal photoemission spectroscopy measurements on n+ InN on GaN epilayers. The photocurrent shows two threshold energies, one at 1.624 eV and the other at 2.527 eV. From these, we obtain the band offsets ΔEv = 0.85 eV and ΔEc = 1.82 eV.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
79.60.Jv Interfaces; heterostructures; nanostructures
68.55.-a Thin film structure and morphology
71.20.Nr Semiconductor compounds
79.60.Bm Clean metal, semiconductor, and insulator surfaces
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