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17 Oct 2011

Volume 99, Issue 16, Articles (16xxxx)

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Appl. Phys. Lett. 99, 163301 (2011); http://dx.doi.org/10.1063/1.3651509 (3 pages)

Jonathan E. Allen, Kevin G. Yager, Htay Hlaing, Chang-Yong Nam, Benjamin M. Ocko, and Charles T. Black
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Effect of interface states on the instability under temperature stress in amorphous SiInZnO thin film transistor

Do Hyung Kim, Hyun Kwang Jung, Dae Hwan Kim, and Sang Yeol Lee

Appl. Phys. Lett. 99, 162101 (2011); http://dx.doi.org/10.1063/1.3645597 (3 pages) | Cited 2 times

Online Publication Date: 17 October 2011

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The instability of amorphous SiInZnO thin-film transistor with different active layer thickness under temperature stress has been investigated using the density of states extracted directly from capacitance-voltage characteristics. Interestingly, it is found that the instability under temperature stress is inversely proportional to the magnitude of interfacial trap density not the total trap density. This was observed from the decrease of the falling rate of activation energy as increasing interfacial trap density. Therefore, the interfacial trap plays a very important role as a key origin for the negative threshold voltage shift under temperature stress in SiInZnO thin-film transistors.
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85.30.Tv Field effect devices

Electrical spin injection and detection at Al2O3/n-type germanium interface using three terminal geometry

A. Jain, L. Louahadj, J. Peiro, J. C. Le Breton, C. Vergnaud, A. Barski, C. Beigné, L. Notin, A. Marty, V. Baltz, S. Auffret, E. Augendre, H. Jaffrès, J. M. George, and M. Jamet

Appl. Phys. Lett. 99, 162102 (2011); http://dx.doi.org/10.1063/1.3652757 (3 pages) | Cited 22 times

Online Publication Date: 18 October 2011

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In this letter, we report on electrical spin injection and detection in n-type germanium-on-insulator using a Co/Py/Al2O3 spin injector and 3-terminal non-local measurements. We observe an enhanced spin accumulation signal of the order of 1 meV consistent with the sequential tunneling process via interface states in the vicinity of the Al2O3/Ge interface. This spin signal is further observable up to 220 K. Moreover, the presence of a strong inverted Hanle effect points out the influence of random fields arising from interface roughness on the injected spins.
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72.25.Mk Spin transport through interfaces
68.35.Ct Interface structure and roughness
73.20.At Surface states, band structure, electron density of states
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.40.Gk Tunneling

Diffusion of tin in germanium: A GGA+U approach

H. Tahini, A. Chroneos, R. W. Grimes, and U. Schwingenschlögl

Appl. Phys. Lett. 99, 162103 (2011); http://dx.doi.org/10.1063/1.3653472 (3 pages) | Cited 9 times

Online Publication Date: 18 October 2011

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Density functional theory calculations are used to investigate the formation and diffusion of tin-vacancy pairs (SnV) in germanium (Ge). Depending upon the Fermi energy, SnV pairs can form in neutral, singly negative, or doubly negative charged states. The activation energies of diffusion, also as function of the Fermi energy, are calculated to lie between 2.48-3.65 eV, in agreement with and providing an interpretation of available experimental work.
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66.30.J- Diffusion of impurities
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.20.Gj Other metals and alloys
61.72.jd Vacancies

Interfacial charge effects on electron transport in III-Nitride metal insulator semiconductor transistors

Ting-Hsiang Hung, Michele Esposto, and Siddharth Rajan

Appl. Phys. Lett. 99, 162104 (2011); http://dx.doi.org/10.1063/1.3653805 (3 pages) | Cited 4 times

Online Publication Date: 18 October 2011

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We report on the calculation of the two dimension electron gas (2DEG) mobility in scaled AlGaN/GaN metal-insulator-semiconductor high-electron-mobility-transistors. We investigate the effect of remote impurity and phonon scattering models on the 2DEG mobility of the dielectric/AlGaN/GaN structure and investigate its variation with dielectric/AlGaN interface charge density, 2DEG concentration, and AlGaN thickness. Remote impurity scattering was found to be the dominant mechanism when the 2DEG density is below 5 × 1012 cm−2 and dielectric/AlGaN interface charge density is above 5 × 1012 cm−2. The interfacial charge has significant effect on the mobility as the AlGaN cap layer thickness is scaled down below 5 nm.
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85.30.Tv Field effect devices

Interaction between Si doping and the polarization-induced internal electric field in the AlGaN/GaN superlattice

Wei Zhang, Yue Zhang, JunShuai Xue, Ying Zhang, Ling Lv, JinCheng Zhang, and Yue Hao

Appl. Phys. Lett. 99, 162105 (2011); http://dx.doi.org/10.1063/1.3655469 (3 pages) | Cited 2 times

Online Publication Date: 20 October 2011

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AlGaN/GaN superlattices (SLs) with and without Si doping exhibit very different properties. Because of the difference between the dielectric constants of AlGaN and GaN, the wells of the SL are depleted in the undoped structure. With increased Si doping in the GaN wells, the depletion effect will vanish, and the accumulation of electrons will compensate for the polarization-induced internal electric field (PIIEF) in the AlGaN barrier, which is followed by disturbance of the PIIEF in the GaN wells due to electron overflow from the ground state E0 to the first excited state E1. This leads to a decrease in E1-E0.
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68.65.Cd Superlattices
73.61.Ey III-V semiconductors
77.22.Ch Permittivity (dielectric function)
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Temperature and bias dependence of Hanle effect in CoFe/MgO/composite Ge

Kun-Rok Jeon, Byoung-Chul Min, Youn-Ho Park, Hun-Sung Lee, Chang-Yup Park, Young-Hun Jo, and Sung-Chul Shin

Appl. Phys. Lett. 99, 162106 (2011); http://dx.doi.org/10.1063/1.3648107 (3 pages) | Cited 9 times

Online Publication Date: 20 October 2011

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We have investigated the temperature and bias dependence of the Hanle effect in a composite n-type Ge system consisting of a heavily doped surface layer and a moderately doped Ge substrate, using three-terminal Hanle measurements. A large spin signal of ∼5.1 kΩμm2 and a spin lifetime of ∼105 ps are obtained at 300 K. The spin signal, spin lifetime, and their asymmetries with respect to the bias polarity have been measured over a temperature range from 5 K to 300 K. Intriguingly, an inverted Hanle effect, indicating the sign inversion of spin polarization in Ge, is observed at low temperature.
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72.25.-b Spin polarized transport
73.40.Cg Contact resistance, contact potential
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Tm Composite materials

Graphene p-n junctions with nonuniform Rashba spin-orbit coupling

Marek Rataj and Józef Barnaś

Appl. Phys. Lett. 99, 162107 (2011); http://dx.doi.org/10.1063/1.3641873 (3 pages) | Cited 4 times

Online Publication Date: 20 October 2011

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Linear conductance of graphene-based p-n junctions with Rashba spin-orbit coupling is considered theoretically. A square potential step is used to model the junctions, while the coupling is introduced in terms of the Kane-Mele model (C. L. Kane and E. J. Mele, Phys. Rev. Lett. 95, 226801 (2005)). The main objective is a description of electronic transport in junctions where Rashba parameter is nonuniform. Such a nonuniformity can appear when graphene is asymmetrically covered with atomic layers, or when Rashba coupling is strongly dependent on electric field. It is shown that conductance is significantly modified by the considered nonuniformity, which is most clearly manifested by an anomalous minimum at a certain potential step height.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.20.At Surface states, band structure, electron density of states
72.20.Fr Low-field transport and mobility; piezoresistance
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
73.25.+i Surface conductivity and carrier phenomena

Shubnikov-de Haas measurement of electron effective mass in GaAs1−xBix

B. Fluegel, R. N. Kini, A. J. Ptak, D. Beaton, K. Alberi, and A. Mascarenhas

Appl. Phys. Lett. 99, 162108 (2011); http://dx.doi.org/10.1063/1.3655198 (3 pages) | Cited 1 time

Online Publication Date: 21 October 2011

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Magnetic field and temperature dependent resistivity measurements on n-type GaAs1-xBix epitaxially grown films show clear Shubnikov de Haas oscillations in the range 0 ≤ x ≤ 0.0088. An overall decrease in the electron effective mass is observed for this range of compositions. Accounting for the known giant bandgap bowing and giant spin orbit bowing, the measured changes in the effective mass are in qualitative agreement with perturbation theory applied to these energy band changes, confirming that bismuth mainly perturbs the valence band. The stronger compositional dependence of the measured mass is attributed to effects from the bismuth isolated state.
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72.20.My Galvanomagnetic and other magnetotransport effects
73.61.Le Other inorganic semiconductors
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

Effect of interfacial oxide layer on the switching uniformity of Ge2Sb2Te5-based resistive change memory devices

Jiyong Woo, Seungjae Jung, Manzar Siddik, Euijun Cha, Sharif Md. Sadaf, and Hyunsang Hwang

Appl. Phys. Lett. 99, 162109 (2011); http://dx.doi.org/10.1063/1.3656247 (3 pages) | Cited 4 times

Online Publication Date: 21 October 2011

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We report the effect of the interfacial oxide layer on switching uniformity in Ge2Sb2Te5 (GST)-based resistive switching memory devices. An interfacial oxide layer acting as an internal resistor was fabricated by the simple thermal oxidation process at low temperature and confirmed by x-ray photoelectron spectroscopy analysis. TiN/oxidized GST/GST/Pt devices showed extremely uniform resistance states owing to intentionally controlled current flow induced by the interfacial oxide layer, despite the filaments being randomly formed. Furthermore, the devices showed good memory performance, e.g., a large on/off resistance ratio (over four orders of magnitude) and reliable data retention (up to 104 s at 85 °C).
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84.30.Sk Pulse and digital circuits
84.32.Ff Conductors, resistors (including thermistors, varistors, and photoresistors)
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