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11 Oct 2010

Volume 97, Issue 15, Articles (15xxxx)

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Appl. Phys. Lett. 97, 154101 (2010); http://dx.doi.org/10.1063/1.3479052 (3 pages)

Younggeun Park, Yeonho Choi, Debkishore Mitra, Taewook Kang, and Luke P. Lee
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Defect-free Ge-on-insulator with (100), (110), and (111) orientations by growth-direction-selected rapid-melting growth

Kaoru Toko, Takanori Tanaka, Yasuharu Ohta, Taizoh Sadoh, and Masanobu Miyao

Appl. Phys. Lett. 97, 152101 (2010); http://dx.doi.org/10.1063/1.3493184 (3 pages) | Cited 4 times

Online Publication Date: 11 October 2010

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Defect-free Ge-on-insulator (GOI) with various crystal orientations is essential to realize high-speed and multifunctional devices. Seeded rapid-melting growth of GOI is investigated as a function of seed-orientations and growth-directions. From (100)-oriented Si seeds, Ge growth with a (100) orientation propagates for all growth-directions, however, rotational-growth is observed for some directions when Si seeds with (110) and (111) orientations are used. Such rotational-growth can be completely suppressed by selecting the growth-directions deviating from 〈111〉 by more than 35°. Transmission-electron-microscopy observation shows no-stacking fault and no-dislocations. Consequently, defect-free GOI with (100), (110), and (111) orientation is achieved, which demonstrates high-hole mobility ( ∼ 1100 cm2/V s).
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81.10.Fq Growth from melts; zone melting and refining
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.61.Cw Elemental semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance

Overlapping-gate architecture for silicon Hall bar field-effect transistors in the low electron density regime

L. H. Willems van Beveren, K. Y. Tan, N. S. Lai, A. S. Dzurak, and A. R. Hamilton

Appl. Phys. Lett. 97, 152102 (2010); http://dx.doi.org/10.1063/1.3501136 (3 pages)

Online Publication Date: 11 October 2010

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We report the fabrication and study of Hall bar field-effect transistors in which an overlapping-gate architecture allows four-terminal measurements of low-density two-dimensional electron systems while maintaining a high density at the Ohmic contacts. Comparison with devices made using a standard single gate show that measurements can be performed at much lower densities and higher channel resistances, despite a reduced peak mobility. We also observe a voltage threshold shift which we attribute to negative oxide charge, injected during electron-beam lithography processing.
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85.30.Tv Field effect devices
85.30.Fg Bulk semiconductor and conductivity oscillation devices (including Hall effect devices, space-charge-limited devices, and Gunn effect devices)
81.05.Cy Elemental semiconductors

Base metal alloys with self-healing native conductive oxides for electrical contact materials

M. Aindow, S. P. Alpay, Y. Liu, J. V. Mantese, and B. S. Senturk

Appl. Phys. Lett. 97, 152103 (2010); http://dx.doi.org/10.1063/1.3499369 (3 pages) | Cited 5 times

Online Publication Date: 12 October 2010

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Base metals for electrical contacts exhibit high bulk conductivities but form low-conductivity native oxide scales in air, leading to unacceptably high contact resistances. Here we show that alloying base metals can lead to higher conductivity native scales by: doping to enhance carrier concentration; inducing mixed oxidation states to give electron/polaron hopping; and/or phase separation for conducting pathways. Data from Cu–La, Fe–V, and Ni–Ru alloys demonstrate the viability of these approaches, yielding contact resistances up to 106 times lower than that for oxidized Cu.
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73.40.Cg Contact resistance, contact potential
73.40.Jn Metal-to-metal contacts
81.65.Mq Oxidation

Thermoelectric properties of bipolar diffusion effect on In4Se3−xTex compounds

Jong-Soo Rhyee, Eunseog Cho, Kyunghan Ahn, Kyu Hyoung Lee, and Sang Mock Lee

Appl. Phys. Lett. 97, 152104 (2010); http://dx.doi.org/10.1063/1.3493269 (3 pages) | Cited 3 times

Online Publication Date: 12 October 2010

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We present thermoelectric properties and electronic structure of the series compounds of In4Se3−xTex (0.0 ≤ x ≤ 3.0). Even if the Te-doping is an isoelectronic substitution, we found that the electron dominated carrier transport in Se-rich region (x ≤ 0.2) evolves into the electron-hole bipolar transport properties in Te-rich region (x ≥ 2.5) from the temperature-dependent thermal conductivity κ(T), Seebeck coefficient S(T), and Hall coefficient RH(T) measurements. The electronic band structures of In4Se3−xTex (x = 0.0, 2.75, and 3.0) are not changed significantly with respect to Te-substitution concentrations. From the Boltzmann transport calculation, the electron-hole bipolar effect on thermoelectric transport properties in Te-rich region can be understood by lowering the chemical potential to the valence band maximum in the Te-rich compounds.
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72.20.Pa Thermoelectric and thermomagnetic effects
72.20.My Galvanomagnetic and other magnetotransport effects
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
66.30.-h Diffusion in solids
71.20.Nr Semiconductor compounds
05.60.-k Transport processes

Effects of back interface trap states on the fully depleted strained-silicon-on-insulator capacitorless single transistor dynamic random access memory cells

Min-Soo Kim and Won-Ju Cho

Appl. Phys. Lett. 97, 152105 (2010); http://dx.doi.org/10.1063/1.3494262 (3 pages)

Online Publication Date: 12 October 2010

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A series of systematic experiments were carried out to investigate the effects of silicon back interface state density between silicon channel layer and buried oxide layer on the memory characteristics. The back interface states of fully depleted strained-silicon-on-insulator (FD sSOI) substrate were intentionally generated by controlling the temperature of rapid thermal annealing (RTA) process and the amount of back interface trap was evaluated by using the backgated metal-oxide-semiconductor field-effect transistor method. As a result, the trap density of back interface increased with RTA temperature, which causes the degradation of FD sSOI single transistor dynamic random access memory.
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84.30.Sk Pulse and digital circuits
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
85.30.Tv Field effect devices

Hydrogen induced passivation of Si interfaces by Al2O3 films and SiO2/Al2O3 stacks

G. Dingemans, W. Beyer, M. C. M. van de Sanden, and W. M. M. Kessels

Appl. Phys. Lett. 97, 152106 (2010); http://dx.doi.org/10.1063/1.3497014 (3 pages) | Cited 21 times

Online Publication Date: 12 October 2010

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The role of hydrogen in Si surface passivation is experimentally identified for Al2O3 (capping) films synthesized by atomic layer deposition. By using stacks of SiO2 and deuterated Al2O3, we demonstrate that hydrogen is transported from Al2O3 to the underlying SiO2 already at relatively low annealing temperatures of 400 °C. This leads to a high level of chemical passivation of the interface. Moreover, the thermal stability of the passivation up to 800 °C was significantly improved by applying a thin Al2O3 capping film on the SiO2. The hydrogen released from the Al2O3 film favorably influences the passivation of Si interface defects.
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81.65.Rv Passivation
71.55.Cn Elemental semiconductors
61.72.Cc Kinetics of defect formation and annealing
68.55.A- Nucleation and growth

Effect of concentration on low-frequency noise of multiwall carbon nanotubes in high-density polyethylene matrix

C. Barone, S. Pagano, and H. C. Neitzert

Appl. Phys. Lett. 97, 152107 (2010); http://dx.doi.org/10.1063/1.3502485 (3 pages) | Cited 3 times

Online Publication Date: 13 October 2010

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Transport and noise measurements of multiwall carbon nanotubes in high-density polyethylene matrix are reported. In these composites current transport occurs through a random tunnel junctions network, formed by adjacent carbon nanotubes. Low-frequency noise investigations reveal a 1/f behavior induced by resistance fluctuations. An unusual temperature dependence in samples with different nanotube concentration is found. This can be explained by a transition from a fluctuation-induced tunneling mechanism to a thermally activated regime, occurring at increasing nanotube concentration and resulting in a decrease in the overall noise.
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73.40.Gk Tunneling
72.80.Tm Composite materials
72.70.+m Noise processes and phenomena

Carbon impurities and the yellow luminescence in GaN

J. L. Lyons, A. Janotti, and C. G. Van de Walle

Appl. Phys. Lett. 97, 152108 (2010); http://dx.doi.org/10.1063/1.3492841 (3 pages) | Cited 36 times

Online Publication Date: 13 October 2010

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Using hybrid functional calculations we investigate the effects of carbon on the electrical and optical properties of GaN. In contrast to the currently accepted view that C substituting for N (CN) is a shallow acceptor, we find that CN has an ionization energy of 0.90 eV. Our calculated absorption and emission lines also indicate that CN is a likely source for the yellow luminescence that is frequently observed in GaN, solving the longstanding puzzle of the nature of the C-related defect involved in yellow emission. Our results suggest that previous experimental data, analyzed under the assumption that CN acts as a shallow acceptor, should be re-examined.
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71.55.Eq III-V semiconductors
73.61.Ey III-V semiconductors
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
61.72.U- Doping and impurity implantation
61.72.Bb Theories and models of crystal defects

Highly tunable hybrid quantum dots with charge detection

C. Rössler, B. Küng, S. Dröscher, T. Choi, T. Ihn, K. Ensslin, and M. Beck

Appl. Phys. Lett. 97, 152109 (2010); http://dx.doi.org/10.1063/1.3501977 (3 pages) | Cited 5 times

Online Publication Date: 14 October 2010

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In order to employ solid state quantum dots as qubits, both a high degree of control over the confinement potential as well as sensitive charge detection are essential. We demonstrate that by combining local anodic oxidation with local Schottky-gates, these criteria are nicely fulfilled in the resulting hybrid device. To this end, a quantum dot with adjacent charge detector is defined. After tuning the quantum dot to contain only a single electron, we are able to observe the charge detector signal of the quantum dot state for a wide range of tunnel couplings.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.63.Kv Quantum dots
73.30.+y Surface double layers, Schottky barriers, and work functions
81.65.-b Surface treatments
81.05.Ea III-V semiconductors

Excited states of the free excitons in CuInSe2 single crystals

M. V. Yakushev, F. Luckert, C. Faugeras, A. V. Karotki, A. V. Mudryi, and R. W. Martin

Appl. Phys. Lett. 97, 152110 (2010); http://dx.doi.org/10.1063/1.3502603 (3 pages) | Cited 5 times

Online Publication Date: 14 October 2010

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High-quality CuInSe2 single crystals were studied using polarization resolved photoluminescence (PL) and magnetophotoluminescence (MPL). The emission lines related to the first (n = 2) excited states for the A and B free excitons were observed in the PL and MPL spectra at 1.0481 meV and 1.0516 meV, respectively. The spectral positions of these lines were used to estimate accurate values for the A and B exciton binding energies (8.5 meV and 8.4 meV, respectively), Bohr radii (7.5 nm), band gaps (EgA = 1.050 eV and EgB = 1.054 eV), and the static dielectric constant (11.3) assuming the hydrogenic model.
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71.35.-y Excitons and related phenomena
71.15.Qe Excited states: methodology
71.15.Nc Total energy and cohesive energy calculations
77.22.Ch Permittivity (dielectric function)
78.55.Hx Other solid inorganic materials

Conducting interfaces between band insulating oxides: The LaGaO3/SrTiO3 heterostructure

P. Perna, D. Maccariello, M. Radovic, U. Scotti di Uccio, I. Pallecchi, M. Codda, D. Marré, C. Cantoni, J. Gazquez, M. Varela, S. J. Pennycook, and F. Miletto Granozio

Appl. Phys. Lett. 97, 152111 (2010); http://dx.doi.org/10.1063/1.3496440 (3 pages) | Cited 14 times

Online Publication Date: 14 October 2010

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We show that the growth of the heterostructure LaGaO3/SrTiO3 yields the formation of a highly conductive interface. Our samples were carefully analyzed by high resolution electron microscopy, in order to assess their crystal perfection and to evaluate the abruptness of the interface. Their carrier density and sheet resistance are compared to the case of LaAlO3/SrTiO3 and a superconducting transition is found. The results open the route to widening the field of polar-nonpolar interfaces, pose some phenomenological constrains to their underlying physics and highlight the chance of tailoring their properties for future applications by adopting suitable polar materials.
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73.40.-c Electronic transport in interface structures
73.20.Fz Weak or Anderson localization

Passivated TiN nanocrystals/SiN trapping layer for enhanced erasing in nonvolatile memory

G. Gay, D. Belhachemi, J. P. Colonna, S. Minoret, P. Brianceau, D. Lafond, T. Baron, G. Molas, E. Jalaguier, A. Beaurain, B. Pelissier, V. Vidal, and B. De Salvo

Appl. Phys. Lett. 97, 152112 (2010); http://dx.doi.org/10.1063/1.3501129 (3 pages) | Cited 7 times

Online Publication Date: 14 October 2010

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We present chemical vapor deposition of titanium nitride nanocrystals (ncs) on silicon nitride (SiN). Ncs are passivated in situ by a silicon shell and encapsulated in SiN. High density (3×1012 cm−2), crystalline and isolated ncs are observed by transmission electron microscopy and characterized by x-ray photoelectron spectroscopy. TiN ncs/SiN are integrated as charge trapping layer in a nonvolatile memory. Devices show large memory window (10 V) and fast erasing compared to devices using pure SiN trapping layer, explained by enhanced electrical field in SiN. Acceptable reliability in terms of cycling and data retention is also demonstrated.
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81.65.Rv Passivation
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
79.60.-i Photoemission and photoelectron spectra
85.30.Tv Field effect devices

The origin of the resistance change in GeSbTe films

Moon Hyung Jang, Seung Jong Park, Sung Jin Park, Mann-Ho Cho, E. Z. Kurmaev, L. D. Finkelstein, and Gap Soo Chang

Appl. Phys. Lett. 97, 152113 (2010); http://dx.doi.org/10.1063/1.3499751 (3 pages) | Cited 1 time

Online Publication Date: 15 October 2010

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Amorphous Ge2Sb2Te5 (a-GST) films were deposited by ion beam sputtering deposition. Extended x-ray absorption fine structure (EXAFS) data confirmed the existence of the Ge–Ge homopolar bonds in the films. Raman spectra also indicated that the Ge tetrahedral coordination in the a-GST film disappeared after an annealing treatment above 220 °C. Resonantly excited Ge L2,3 x-ray emission spectra (which probe occupied Ge 3d4s-electronic states) show that the phase change from the amorphous to crystalline state is accompanied by a reduction in the Ge I(L2)/I(L3) intensity ratio due to a L2L3N Coster–Kronig transition, indicating that the number of carriers is increased in the Ge 4sp valence state. These findings constitute direct evidence for the contribution of the Ge electronic states to the resistivity change.
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73.61.Jc Amorphous semiconductors; glasses
81.05.Gc Amorphous semiconductors
81.15.Cd Deposition by sputtering
68.55.ag Semiconductors
61.43.Dq Amorphous semiconductors, metals, and alloys
71.23.Cq Amorphous semiconductors, metallic glasses, glasses
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