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4 Apr 2005

Volume 86, Issue 14, Articles (14xxxx)

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Appl. Phys. Lett. 86, 142101 (2005); http://dx.doi.org/10.1063/1.1895476 (3 pages)

M. Hanke, T. Boeck, A.-K. Gerlitzke, F. Syrowatka, F. Heyroth, and R. Köhler
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Size, shape, and ordering of SiGe/Si(001) islands grown by means of liquid phase epitaxy under far-nonequilibrium growth conditions

M. Hanke, T. Boeck, A.-K. Gerlitzke, F. Syrowatka, F. Heyroth, and R. Köhler

Appl. Phys. Lett. 86, 142101 (2005); http://dx.doi.org/10.1063/1.1895476 (3 pages) | Cited 2 times

Online Publication Date: 28 March 2005

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Applying scanning electron microscopy, we have studied the evolution of shape and lateral positional correlation of Si1−xGex/Si(001) Stranski–Krastanov islands grown by means of liquid phase epitaxy (LPE). However, in contrast to conventional near-equilibrium LPE, a distinctly higher cooling rate of 10 K/min ensures extremly nonequilibrium growth conditions. The facet inclination of subsequent island stages decreases from nearly vertical sidewalls toward {111}- and {101}-type facets. Energy dispersive x-ray microanalysis yields a size-independent germanium content of 8.9% within islands between 760 and 1700 nm base width which is—by more than a factor of 2—smaller than islands of the same concentration grown in a near-equilibrium LPE process. Square-like formations of subsequently smaller islands around a large central island indicate only next to island interactions during the lateral self-assembling.
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81.05.Hd Other semiconductors
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Ct Interface structure and roughness
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)

Controlled orientation of liquid-crystalline polythiophene semiconductors for high-performance organic thin-film transistors

Yiliang Wu, Ping Liu, Beng S. Ong, Tharan Srikumar, Ni Zhao, Gianluigi Botton, and Shiping Zhu

Appl. Phys. Lett. 86, 142102 (2005); http://dx.doi.org/10.1063/1.1894597 (3 pages) | Cited 53 times

Online Publication Date: 29 March 2005

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The silane self-assembled monolayer (SAM) modification of a SiO2 gate dielectric surface improved the molecular ordering of organic channel semiconductor in organic thin-film transistors (OTFTs), leading to a significant improvement in transistor performance. Mobility of up to 0.18 cm2/V s (current on∕off ratio of 107) was obtained for OTFTs with a liquid-crystalline polythiophene semiconductor built on an octyltrichlorosilane-modified SiO2 gate dielectric layer, a 450 times improvement over those built on a nonmodified dielectric layer. The mobility enhancement was attributed to the edge-on orientation of the polythiophene molecules induced by the silane SAM layer as deduced from the crystal domain structures in the atomic force microscopic images.
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85.30.Tv Field effect devices
85.65.+h Molecular electronic devices
68.37.Ps Atomic force microscopy (AFM)
73.50.Dn Low-field transport and mobility; piezoresistance
77.55.-g Dielectric thin films

Physical mechanisms of negative-bias temperature instability

L. Tsetseris, X. J. Zhou, D. M. Fleetwood, R. D. Schrimpf, and S. T. Pantelides

Appl. Phys. Lett. 86, 142103 (2005); http://dx.doi.org/10.1063/1.1897075 (3 pages) | Cited 26 times

Online Publication Date: 28 March 2005

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We report first-principles calculations that elucidate the mechanisms that underlie key features of negative-bias temperature instability (NBTI). We show that the depassivation of Si–H bonds by protons released in the Si substrate is consistent with the observed increase in interface-trap density. The calculated activation energy of 0.36 eV is in excellent agreement with observations for long stress times. Adequate amounts of hydrogen, needed to initiate depassivation, are likely to exist in the substrate, trapped in complexes with dopants. The role of holes in the H release mechanism is identified. Finally, we explain how the above mechanisms can account for various experimental NBTI observations.
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85.30.De Semiconductor-device characterization, design, and modeling

Radiative and nonradiative recombination processes in InN films grown by metal organic chemical vapor deposition

R. Intartaglia, B. Maleyre, S. Ruffenach, O. Briot, T. Taliercio, and B. Gil

Appl. Phys. Lett. 86, 142104 (2005); http://dx.doi.org/10.1063/1.1897428 (3 pages) | Cited 21 times

Online Publication Date: 28 March 2005

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The 800 meV photoluminescence band in indium nitride is excited under pulsed excitation conditions and is investigated as a function of temperature and time. Our results are consistent with a composite photoluminescence feature composed of two overlapping bands separated by an ∼ 10 meV splitting, with populations described by a thermal equilibrium model. Efficient nonradiative recombination channels rule both the temperature dependence of the time-integrated photoluminescence spectra and the recombination dynamics. At 10 K, the radiative recombination time is of the order of 300 ns, while the nonradiative recombination time, which is ruled by activation energy of 8 meV, is about 100 ps.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.45.Wx Polymers and organic materials in electrochemistry
82.50.-m Photochemistry

Femtosecond spectroscopy of unipolar nanometer-scale high-field transport of holes in Al0.08Ga0.92As

S. Trumm, M. Betz, F. Sotier, A. Leitenstorfer, A. Schwanhäußer, M. Eckardt, S. Malzer, M. Hanson, D. Driscoll, A. C. Gossard, and G. H. Döhler

Appl. Phys. Lett. 86, 142105 (2005); http://dx.doi.org/10.1063/1.1898442 (3 pages) | Cited 1 time

Online Publication Date: 29 March 2005

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High-field transport in GaAs is investigated tracing ultrafast modifications of the Franz–Keldysh absorption spectrum of a AlxGa1−xAs heterostructure diode. A sophisticated sample design allows us to isolate the unipolar tranport properties of holes in combination with a nanometer scale definition of layers for both photoexcitation and detection of the propagating carrier distribution. Transient velocities and spatial broadening of the hole ensemble are directly measured for electric fields between 15 and 200 kV∕cm comparing room temperature operation to results for TL = 4 K. Even at low temperatures, the transient hole velocities are found not to exceed a value of 1.2×107 cm/s which is a result of ultrafast optical phonon emission with a scattering time below 25 fs.
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85.30.Kk Junction diodes
73.40.Ty Semiconductor-insulator-semiconductor structures
73.50.Fq High-field and nonlinear effects
78.20.Jq Electro-optical effects
78.47.-p Spectroscopy of solid state dynamics

Role of interface traps on breakdown process of a magnetic tunnel junction

Kwang-Seok Kim and B. K. Cho

Appl. Phys. Lett. 86, 142106 (2005); http://dx.doi.org/10.1063/1.1897846 (3 pages) | Cited 8 times

Online Publication Date: 30 March 2005

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Time dependent dielectric breakdown (TDDB) measurements were carried out for magnetic tunneling junctions (MTJs) with different electron trap densities at the interface between a bottom electrode and an insulating barrier. The TDDB shows a strong bias-polarity dependence, which becomes bigger with increasing trap density. In addition, the current creep before total dielectric breakdown consistently shows bias-polarity dependence. The polarity dependence of the breakdown in MTJs with an ultrathin tunneling barrier (15–20 Å) is believed to be caused by precursor effect of the traps at the bottom interface, which enhances the trap generation rate in a tunneling barrier, resulting in acceleration of the breakdown process.
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75.50.Bb Fe and its alloys
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
73.21.Ac Multilayers
75.47.Np Metals and alloys
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
77.22.Jp Dielectric breakdown and space-charge effects
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Diffusion and dissociation mechanisms of vacancy-oxygen complex in silicon

Masayuki Furuhashi and Kenji Taniguchi

Appl. Phys. Lett. 86, 142107 (2005); http://dx.doi.org/10.1063/1.1897433 (3 pages) | Cited 7 times

Online Publication Date: 30 March 2005

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We are examining diffusion mechanisms of the vacancy-oxygen complex (VO) in bulk Si using ab initio calculations based on a 64-atom supercell. We found two atomic mechanisms involved in the VO diffusion; one is caused by migration of an interstitial oxygen atom, another by migration of a vacancy. The energy barrier of the mechanism due to an oxygen migration is 2.02 eV, and that caused by a vacancy migration is 1.98 eV. These energy barriers are close to the experimental activation energy of 2.0 eV required for the dissociation and diffusion of VO. The derived activation energies of the two mechanisms suggest that these mechanisms plausibly occur simultaneously. In addition, we clarify that the dissociation energy of VO, 1.85 eV, is lower than the diffusion energy of VO.
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68.08.-p Liquid-solid interfaces
64.70.-p Specific phase transitions
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