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21 Sep 2009

Volume 95, Issue 12, Articles (12xxxx)

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Appl. Phys. Lett. 95, 121104 (2009); http://dx.doi.org/10.1063/1.3231448 (3 pages)

E. H. Khoo, I. Ahmed, and E. P. Li
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Experimental measurement of negative index in an all-dielectric metamaterial

T. Lepetit, É. Akmansoy, and J.-P. Ganne

Appl. Phys. Lett. 95, 121101 (2009); http://dx.doi.org/10.1063/1.3232222 (3 pages) | Cited 3 times

Online Publication Date: 21 September 2009

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We designed and fabricated an all-dielectric metamaterial which exhibits negative index of refraction. This metamaterial consists of one layer made up of two sets of high permittivity resonators. We experimentally showed that this metamaterial exhibits resonant effective permeability and permittivity issued from the first two modes of Mie resonances, respectively, and that matching both these parameters results in negative effective index.
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42.70.-a Optical materials
42.25.Fx Diffraction and scattering
42.25.-p Wave optics

Relaxation and emission of Bragg-mode and cavity-mode polaritons in a ZnO microcavity at room temperature

S. Faure, C. Brimont, T. Guillet, T. Bretagnon, B. Gil, F. Médard, D. Lagarde, P. Disseix, J. Leymarie, J. Zúñiga-Pérez, M. Leroux, E. Frayssinet, J. C. Moreno, F. Semond, and S. Bouchoule

Appl. Phys. Lett. 95, 121102 (2009); http://dx.doi.org/10.1063/1.3232228 (3 pages) | Cited 10 times

Online Publication Date: 21 September 2009

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The strong coupling regime in a ZnO microcavity is investigated through room temperature photoluminescence and reflectivity experiments. The simultaneous strong coupling of excitons to the cavity mode and the first Bragg mode is demonstrated at room temperature. The polariton relaxation is followed as a function of the excitation density, showing a nonthermal polariton distribution. A relaxation bottleneck is evidenced in the Bragg-mode polariton branch. It is partly broken under strong excitation density, so that the emission from this branch dominates the one from cavity-mode polaritons.
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71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
78.55.Et II-VI semiconductors
71.35.-y Excitons and related phenomena

Transmission interference tuned by an external static magnetic field in a two-slit structure

Bin Hu, Ben-Yuan Gu, Yan Zhang, and Ming Liu

Appl. Phys. Lett. 95, 121103 (2009); http://dx.doi.org/10.1063/1.3232227 (3 pages) | Cited 1 time

Online Publication Date: 21 September 2009

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We present a near-field analysis of transmitted field interference tuned by an external static magnetic field on an n-doped semiconductor film drilled by two slits at terahertz frequency. It is found that the peak magnetic field intensity of the interference pattern between the two slits can be strengthened twice as against that of zero external static magnetic field. The physical origin comes from the interaction between surface plasmon polaritons (SPPs) and radiative evanescent field components launched by each slit on the transmitted surface, and also from the considerable alteration of the SPPs, caused by the external static magnetic field.
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78.66.-w Optical properties of specific thin films
78.70.Gq Microwave and radio-frequency interactions
77.22.Ch Permittivity (dielectric function)
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)
68.55.ag Semiconductors

Enhancement of light energy extraction from elliptical microcavity using external magnetic field for switching applications

E. H. Khoo, I. Ahmed, and E. P. Li

Appl. Phys. Lett. 95, 121104 (2009); http://dx.doi.org/10.1063/1.3231448 (3 pages) | Cited 2 times

Online Publication Date: 21 September 2009

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In this letter, the extraction efficiency of light energy from an elliptically shaped microcavity laser is enhanced with external magnetic field. The magnetic field causes electrons to accumulate on the minor arc edge of the elliptical microcavity due to Lorentz force. As a result, the field amplitude at the minor arc edge is higher, and this improves light energy tunneling mechanism from the edge. The extraction efficiency from the microcavity increases by more than 30% after the application of magnetic field. Alternating the direction of the magnetic field allows the elliptical microcavity to function as a switching device.
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42.55.Sa Microcavity and microdisk lasers
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.55.Px Semiconductor lasers; laser diodes

Metallic nanoparticles as intermediate reflectors in tandem solar cells

Stephan Fahr, Carsten Rockstuhl, and Falk Lederer

Appl. Phys. Lett. 95, 121105 (2009); http://dx.doi.org/10.1063/1.3232230 (3 pages) | Cited 17 times

Online Publication Date: 22 September 2009

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Tandem thin film solar cells made of amorphous and microcrystalline silicon offer the potential for high conversion efficiencies at low costs. However, their finite thickness imposed by intrinsic materials properties hinders the complete absorption of light and requires smart photon management. We reveal a genuine strategy to use metallic nanoparticles, appropriately tailored to provide a spectrally selective reflection, as an intermediate reflector. It enhances foremost light absorption in the top cell. We show that the current density for an optimized cell can be 1.16 times larger when compared to a cell without a spectrally selective intermediate reflector.
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84.60.Jt Photoelectric conversion
68.55.-a Thin film structure and morphology
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
81.07.Bc Nanocrystalline materials

Enhanced absorption of metals over ultrabroad electromagnetic spectrum

A. Y. Vorobyev, A. N. Topkov, O. V. Gurin, V. A. Svich, and Chunlei Guo

Appl. Phys. Lett. 95, 121106 (2009); http://dx.doi.org/10.1063/1.3227668 (3 pages) | Cited 10 times

Online Publication Date: 22 September 2009

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Metals are usually highly reflective for electromagnetic waves, especially at far-infrared and terahertz frequencies. Using a femtosecond laser structuring technique, near-perfectly reflective metals are transformed to highly absorptive over an ultrabroad electromagnetic spectrum, ranging from ultraviolet to terahertz. Absorptance of the processed metal is directly measured in the terahertz region using a calorimetry technique, and the measurements show that absorptance of the processed metal is enhanced by more than thirty times over its intrinsic value.
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78.70.Gq Microwave and radio-frequency interactions
78.47.-p Spectroscopy of solid state dynamics
78.30.Er Solid metals and alloys
78.40.Kc Metals, semimetals, and alloys

Efficiency retention at high current injection levels in m-plane InGaN light emitting diodes

X. Li, X. Ni, J. Lee, M. Wu, Ü. Özgür, H. Morkoç, T. Paskova, G. Mulholland, and K. R. Evans

Appl. Phys. Lett. 95, 121107 (2009); http://dx.doi.org/10.1063/1.3236538 (3 pages) | Cited 20 times

Online Publication Date: 22 September 2009

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We investigated the internal quantum efficiency (IQE) and the relative external quantum efficiency (EQE) of m-plane InGaN light emitting diodes (LEDs) grown on m-plane freestanding GaN emitting at ∼ 400 nm for current densities up to 2500 A/cm2. IQE values extracted from intensity and temperature dependent photoluminescence measurements were consistently higher, by some 30%, for the m-plane LEDs than for reference c-plane LEDs having the same structure, e.g., 80% versus 60% at an injected steady-state carrier concentration of 1.2×1018 cm−3. With increasing current injection up to 2500 A/cm2, the maximum EQE is nearly retained in m-plane LEDs, whereas c-plane LEDs exhibit approximately 25% droop. The negligible droop in m-plane LEDs is consistent with the reported enhanced hole carrier concentration and light holes in m-plane orientation, thereby enhanced hole transport throughout the active region, and lack of polarization induced field. A high quantum efficiency and in particular its retention at high injection levels bode well for m-plane LEDs as candidates for general lighting applications.
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85.60.Jb Light-emitting devices
72.20.-i Conductivity phenomena in semiconductors and insulators
78.55.Cr III-V semiconductors

Nanoscale optical tomography using volume-scanning near-field microscopy

Jin Sun, John C. Schotland, Rainer Hillenbrand, and P. Scott Carney

Appl. Phys. Lett. 95, 121108 (2009); http://dx.doi.org/10.1063/1.3224177 (3 pages) | Cited 7 times

Online Publication Date: 23 September 2009

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The relationship between sample structure and data in volume-scanning backscattering mode near-field optical microscopy is investigated. It is shown that the three-dimensional structure of a dielectric sample is encoded in the phase and amplitude of the scattered field and that an approximate reconstruction of the sample structure may be obtained.
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42.30.Wb Image reconstruction; tomography

Mach–Zehnder–Fano interferometer

Andrey E. Miroshnichenko and Yuri S. Kivshar

Appl. Phys. Lett. 95, 121109 (2009); http://dx.doi.org/10.1063/1.3232224 (3 pages) | Cited 7 times

Online Publication Date: 24 September 2009

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We introduce a concept of the Mach–Zehnder–Fano interferometer by inserting a cavity exhibiting Fano resonance into a conventional interferometer. By employing the scattering-matrix approach, we demonstrate that the transmission becomes sensitive to a position of the cavity such that an asymmetric structure exhibits a series of narrow resonances with almost perfect reflection. We discuss how to implement this novel geometry in two-dimensional photonic crystals and use direct numerical simulations to demonstrate novel regimes of the resonant transmission and reflection.
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42.70.Qs Photonic bandgap materials
07.60.Ly Interferometers
02.10.Yn Matrix theory

The effect of absorber doping on electrical and optical properties of nBn based type-II InAs/GaSb strained layer superlattice infrared detectors

Stephen Myers, Elena Plis, Arezou Khoshakhlagh, Ha Sul Kim, Yagya Sharma, Ralph Dawson, Sanjay Krishna, and Aaron Gin

Appl. Phys. Lett. 95, 121110 (2009); http://dx.doi.org/10.1063/1.3230069 (3 pages) | Cited 2 times

Online Publication Date: 24 September 2009

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We have investigated the electrical and optical properties of a nBn based InAs/GaSb strained layer superlattice detector as a function of absorber region background carrier concentration. Temperature dependent dark current, responsivity, and detectivity were measured. The device with a nonintentionally doped absorption region demonstrated the lowest dark current density with a specific detectivity at zero bias equal to 1.2×1011 cm Hz1/2/W at 77 K. This value decreased to 6×1010 cm Hz1/2/W at 150 K. This contrasts significantly with p-i-n diodes, in which the D∗ decreases by over two orders of magnitude from 77 to 150 K, making nBn devices promising for higher operating temperatures.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.30.Kk Junction diodes
61.72.uj III-V and II-VI semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance
73.63.-b Electronic transport in nanoscale materials and structures
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials

Strain effects in group-III nitrides: Deformation potentials for AlN, GaN, and InN

Qimin Yan, Patrick Rinke, Matthias Scheffler, and Chris G. Van de Walle

Appl. Phys. Lett. 95, 121111 (2009); http://dx.doi.org/10.1063/1.3236533 (3 pages) | Cited 37 times

Online Publication Date: 24 September 2009

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A systematic density functional theory study of strain effects on the electronic band structure of the group-III nitrides (AlN, GaN, and InN) is presented. To overcome the deficiencies of the local-density and generalized gradient approximations the Heyd–Scuseria–Ernzerhof (HSE) hybrid functional is used. Cross checks for GaN demonstrate good agreement between HSE and exact-exchange based G0W0 calculations. We observe a pronounced nonlinear dependence of band-energy differences on strain. For realistic strain conditions in the linear regime around the experimental equilibrium volume a consistent and complete set of deformation potentials is derived.
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71.20.Nr Semiconductor compounds
81.05.Ea III-V semiconductors
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity

Photocarrier recombination dynamics in highly excited SrTiO3 studied by transient absorption and photoluminescence spectroscopy

Yasuhiro Yamada, Hideki Yasuda, Takeshi Tayagaki, and Yoshihiko Kanemitsu

Appl. Phys. Lett. 95, 121112 (2009); http://dx.doi.org/10.1063/1.3238269 (3 pages) | Cited 9 times

Online Publication Date: 25 September 2009

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We studied photocarrier recombination processes in highly excited SrTiO3 crystals using pump-probe transient absorption (TA) and photoluminescence (PL) spectroscopy at room temperature. TA signals of nondoped SrTiO3 crystals clearly appear in the visible and infrared spectral region under intense interband photoexcitation, and TA spectra show Drude-like photon-energy dependence. Both TA and PL decay curves are well explained by the same simple rate equation including three-body Auger recombination and single-carrier trapping.
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72.40.+w Photoconduction and photovoltaic effects
72.80.Sk Insulators
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.40.Ha Other nonmetallic inorganics
78.30.Hv Other nonmetallic inorganics
78.55.Hx Other solid inorganic materials
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