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2 Feb 2004

Volume 84, Issue 5, pp. 645-830

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Appl. Phys. Lett. 84, 810 (2004); http://dx.doi.org/10.1063/1.1644924 (3 pages)

Hendrik F. Hamann, Yves C. Martin, and H. Kumar Wickramasinghe
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Importance of electron-impurity scattering for electron transport in terahertz quantum-cascade lasers

Hans Callebaut, Sushil Kumar, Benjamin S. Williams, Qing Hu, and John L. Reno

Appl. Phys. Lett. 84, 645 (2004); http://dx.doi.org/10.1063/1.1644337 (3 pages) | Cited 48 times

Online Publication Date: 27 January 2004

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Using an ensemble Monte Carlo simulation, including both electron–electron and electron–phonon scattering as well as electron-impurity scattering, the current density, population inversion, electron temperature, and gain in two THz quantum-cascade structures are investigated and compared to measurements. We find that the inclusion of electron-impurity scattering in the calculations is crucial when modeling the intersubband transport dynamics in these devices. However, the calculated gain is higher than inferred from experiments. This can be attributed to wavefunction localization caused by dephasing scattering, which is unaccounted for in the present model.© 2004 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
73.61.Ey III-V semiconductors
72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)

Single photon emission from site-controlled pyramidal quantum dots

M. H. Baier, E. Pelucchi, E. Kapon, S. Varoutsis, M. Gallart, I. Robert-Philip, and I. Abram

Appl. Phys. Lett. 84, 648 (2004); http://dx.doi.org/10.1063/1.1643533 (3 pages) | Cited 41 times

Online Publication Date: 27 January 2004

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We demonstrate that a single photoexcited InGaAs semiconductor quantum dot (QD) grown by organo-metallic chemical vapor deposition on prepatterned substrates emits one photon at a time, with no uncontrolled background photon emission, making it an excellent single photon emitter. Moreover, our fabrication technique offers complete site control and small inhomogeneous broadening of QD arrays, which is essential for the practical implementation of QDs in efficient solid-state single photon emitting devices. © 2004 American Institute of Physics.
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78.67.Hc Quantum dots
42.50.-p Quantum optics
68.65.Hb Quantum dots (patterned in quantum wells)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Tunable microdisk resonators vertically coupled to bus waveguides using epitaxial regrowth and wafer bonding techniques

Seung June Choi, Zhen Peng, Qi Yang, Sang Jun Choi, and P. Daniel Dapkus

Appl. Phys. Lett. 84, 651 (2004); http://dx.doi.org/10.1063/1.1644915 (3 pages) | Cited 3 times

Online Publication Date: 27 January 2004

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We demonstrate two different types of tunable microdisk resonators vertically coupled to bus waveguides: a microdisk resonator coupled to air-guided rib bus waveguides and the other one built on buried heterostructure bus lines, respectively. The latter type contacts the substrate without relying on an extra supporting structure, which affords more reliable conductive paths toward the substrate. A planarized epitaxial regrowth technology combined with wafer bonding is used to fabricate the structure. The measured transmission spectra indicate improved tuning capability of buried-bus-coupled microdisks, but the overall device performance is limited by optical leakage through the substrate. © 2004 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays

Parallel plate THz transmitter

S. Coleman and D. Grischkowsky

Appl. Phys. Lett. 84, 654 (2004); http://dx.doi.org/10.1063/1.1644923 (3 pages) | Cited 22 times

Online Publication Date: 27 January 2004

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A THz transmitter that directly excites the guided wave modes of a dielectric filled parallel plate waveguide is demonstrated. When coupled to free space, the transmitter yields a large peak time-domain THz signal. The device yields significant signal amplitudes with varying output spectra with and without a bias field applied. This transmitter provides powerful direct excitation of guided wave modes and is the next step toward an integrated guided wave transverse-electromagnetic mode THz bandwidth device. © 2004 American Institute of Physics.
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84.40.Az Waveguides, transmission lines, striplines
84.40.Ua Telecommunications: signal transmission and processing; communication satellites

Total reflection amorphous carbon mirrors for vacuum ultraviolet free electron lasers

B. Steeg, L. Juha, J. Feldhaus, S. Jacobi, R. Sobierajski, C. Michaelsen, A. Andrejczuk, and J. Krzywinski

Appl. Phys. Lett. 84, 657 (2004); http://dx.doi.org/10.1063/1.1645320 (3 pages) | Cited 13 times

Online Publication Date: 27 January 2004

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Sputter-deposited amorphous carbon coatings of high optical quality and very high radiation stability will be used as reflecting optical elements for free electron laser (FEL) applications in the vacuum ultraviolet (VUV) and soft x-ray spectral regions. Their reflectivity at grazing angles of 2° is typically 94–96% for photon energies between 50 and 250 eV. Using the focused radiation (λ = 98 nm) of the VUV FEL at Deutsches Elektronen-Synchrotron DESY the damage threshold of such coatings was determined to 0.07 J/cm2. Ripples with a spatial period of 76 nm were found on the surfaces damaged by the FEL radiation. © 2004 American Institute of Physics.
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42.79.Bh Lenses, prisms and mirrors
41.60.Cr Free-electron lasers
68.55.-a Thin film structure and morphology
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Silicidation-induced band gap shrinkage in Ge epitaxial films on Si

Jifeng Liu, Douglas D. Cannon, Kazumi Wada, Yasuhiko Ishikawa, Samerkhae Jongthammanurak, David T. Danielson, Jurgen Michel, and Lionel C. Kimerling

Appl. Phys. Lett. 84, 660 (2004); http://dx.doi.org/10.1063/1.1644618 (3 pages) | Cited 17 times

Online Publication Date: 27 January 2004

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Ge epitaxial films on Si grown at high temperatures show a shrinkage in the direct band gap EgΓ as a result of the tensile strain accumulated during the cooling process after growth, making it a promising candidate for effective photon detection in L-band telecommunications. However, because of strain relaxation at temperatures >750 °C, only about 0.20% tensile strain can be accumulated at most. This leads to a direct band gap of 0.773 eV, corresponding to 1605 nm and is not enough to cover the whole L band (1561–1620 nm). In this letter, we report the strain enhancement in epitaxial Ge films induced by the formation of C54TiSi2 on the backside of the Si wafers. The backside C54-TiSi2 layer not only forms a good electric contact, but also increases the tensile strain of the Ge film on the front side from 0.20% to 0.24% and a further direct band gap shrinkage from 0.773 to 0.765 eV, corresponding to 1620 nm, which covers the whole L band. Since the silicidation process is compatible with Si complementary metal-oxide-semiconductor technology, this technique is promising to achieve low cost L-band photon detection completely with tensile strained Ge on Si. © 2004 American Institute of Physics.
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68.60.Bs Mechanical and acoustical properties
78.66.Db Elemental semiconductors and insulators

High transmission and single-mode operation in low-index-contrast photonic crystal waveguide devices

M. Augustin, H.-J. Fuchs, D. Schelle, E.-B. Kley, S. Nolte, A. Tünnermann, R. Iliew, C. Etrich, U. Peschel, and F. Lederer

Appl. Phys. Lett. 84, 663 (2004); http://dx.doi.org/10.1063/1.1644336 (3 pages) | Cited 9 times

Online Publication Date: 27 January 2004

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We investigate photonic crystal films made of low-index glass materials. Polarization-sensitive waveguiding and single-mode operation (with losses as low as 1.7 dB/mm) have been observed in wide multimode photonic crystal waveguides after propagation of some millimeters. Furthermore, single-mode operation and transmission as high as about 50% per bend has been observed experimentally in low-index photonic crystal waveguide bends. © 2004 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.79.Gn Optical waveguides and couplers

Visible spectrum (645 nm) transverse electric field laser operation of InP quantum dots coupled to tensile strained In0.46Ga0.54P quantum wells

G. Walter, J. Elkow, N. Holonyak, R. D. Heller, X. B. Zhang, and R. D. Dupuis

Appl. Phys. Lett. 84, 666 (2004); http://dx.doi.org/10.1063/1.1645674 (3 pages) | Cited 11 times

Online Publication Date: 27 January 2004

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Data are presented that demonstrate the continuous wave room-temperature transverse-electric field (TE) visible-spectrum (645 nm) heterostructure laser operation of single-layer compressively strained 3.75 monolayer equivalent InP quantum dots (QDs) coupled to 60 Å wide tensile-strained In0.46Ga0.54P quantum wells (QWs). The simple stripe geometry (200 μm×4 μm) InP QD+InGaP QW heterostructure laser is capable of high performance despite the coupling of two competing recombination systems. The InP QD+InGaP QW laser exhibits low threshold (∼31 mA), high quantum efficiency (72%, ∼1.38 mW/mA), a relatively high characteristic temperature T0 of 69 K, and a shift in wavelength at temperature of 0.19 nm/°C. © 2004 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes

Enhancement of evanescent waves in waveguides using metamaterials of negative permittivity and permeability

De-Kui Qing and Gang Chen

Appl. Phys. Lett. 84, 669 (2004); http://dx.doi.org/10.1063/1.1645658 (3 pages) | Cited 20 times

Online Publication Date: 27 January 2004

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Electromagnetic waves in waveguides consisting of metamaterials with negative permittivity and permeability are analyzed. It is found that metamaterials can enhance the intensity of the evanescent waves in the cladding without altering the propagation constant of the waveguide for both TE and TM modes. This is a unique property of metamaterials. The enhancement factor increases with the increasing of the thickness of the metamaterial and saturates when complete surface polaritons were established at the interface between the metamaterial and the cladding. The enhancement effect can improve the performance of evanescent-wave-based waveguide devices. © 2004 American Institute of Physics.
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84.40.Az Waveguides, transmission lines, striplines
77.22.Ch Permittivity (dielectric function)
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)

Design of white light-emitting diodes using InGaN/AlInGaN quantum-well structures

D. Xiao, K. W. Kim, S. M. Bedair, and J. M. Zavada

Appl. Phys. Lett. 84, 672 (2004); http://dx.doi.org/10.1063/1.1644920 (3 pages) | Cited 20 times

Online Publication Date: 27 January 2004

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Based on the Rashba–Sheka–Pikus Hamiltonian in the vicinity of the Γ point, and taking into consideration spontaneous and piezoelectric polarization, the optical intensity of nitride-based quantum-well light-emitting diodes has been calculated. It is found that strain substantially alters the subband structure and thus the output intensity of these nitride-biased quantum-well light-emitting diodes. A design that uses AlInGaN as the quantum barrier is proposed to realize efficient red emission, which is hard to achieve if GaN is used as the barrier. In the proposed design, three different InGaN/AlInGaN quantum-well structures emit red, green, and blue light of similar intensity. Also, to achieve high efficiency, important factors related to the oscillator strength are discussed in detail. © 2004 American Institute of Physics.
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73.21.Fg Quantum wells
78.67.De Quantum wells
85.60.Jb Light-emitting devices
85.30.De Semiconductor-device characterization, design, and modeling
78.55.Cr III-V semiconductors
73.20.At Surface states, band structure, electron density of states
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