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18 Oct 2010

Volume 97, Issue 16, Articles (16xxxx)

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Appl. Phys. Lett. 97, 162901 (2010); http://dx.doi.org/10.1063/1.3501139 (3 pages)

Wei-Feng Rao, Ke-Wei Xiao, Tian-Le Cheng, Jie E. Zhou, and Yu U. Wang
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Diamagnetic shift of the A free exciton in CuGaSe2 single crystals

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

Appl. Phys. Lett. 97, 162101 (2010); http://dx.doi.org/10.1063/1.3502608 (3 pages) | Cited 5 times

Online Publication Date: 18 October 2010

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Single crystals of CuGaSe2 were studied using magnetophotoluminescence in magnetic fields up to 20 T at 4.2 K. The rate of the diamagnetic shift in the A free exciton peak was determined to be 9.82×10−6 eV/T2. This rate was used to calculate the reduced mass as 0.115m0, the binding energy as 12.9 meV, the Bohr radius as 5.1 nm and an effective hole mass of 0.64m0 (m0 is the free electron mass) of the free A exciton using a low-field perturbation approach and the hydrogenic model.
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75.20.Ck Nonmetals
71.35.-y Excitons and related phenomena
78.55.Hx Other solid inorganic materials
71.15.Nc Total energy and cohesive energy calculations

Carrier-suppressing effect of scandium in InZnO systems for solution-processed thin film transistors

Yuri Choi, Gun Hee Kim, Woong Hee Jeong, Jung Hyeon Bae, Hyun Jae Kim, Jae-Min Hong, and Jae-Woong Yu

Appl. Phys. Lett. 97, 162102 (2010); http://dx.doi.org/10.1063/1.3503964 (3 pages) | Cited 2 times

Online Publication Date: 19 October 2010

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The carrier-suppressing effect of Sc in InZnO systems was studied using thin-film transistors (TFTs) with a sol-gel processed active channel. As the amount of Sc content increased, the off current decreased, and the threshold voltage shifted to a positive bias region. The Sc effectively controlled the oxygen vacancies and supplied free electrons. X-ray photoelectron spectroscopy (XPS) verified that the vacancy-related oxygen 1s peak decreased with increasing Sc content. The TFT performance with 14% Sc showed that a field-effect mobility and on-off ratio were 2.06 cm2/V s and 8.02×106, respectively.
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85.30.Tv Field effect devices

Very low surface recombination velocities on p- and n-type c-Si by ultrafast spatial atomic layer deposition of aluminum oxide

Florian Werner, Boris Veith, Veronica Tiba, Paul Poodt, Fred Roozeboom, Rolf Brendel, and Jan Schmidt

Appl. Phys. Lett. 97, 162103 (2010); http://dx.doi.org/10.1063/1.3505311 (3 pages) | Cited 7 times

Online Publication Date: 20 October 2010

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Using aluminum oxide (Al2O3) films deposited by high-rate spatial atomic layer deposition (ALD), we achieve very low surface recombination velocities of 6.5 cm/s on p-type and 8.1 cm/s on n-type crystalline silicon wafers. Using spatially separated reaction zones instead of the conventional time-sequenced precursor dosing enables growth rates up to 70 nm/min, whereas conventional ALD limits the growth rate to <2 nm/min. The excellent passivation level is predominantly assigned to a high negative fixed charge density of Qf = −(4±1)×1012 cm−2 in the Al2O3 films. We demonstrate an excellent thermal stability of the passivation quality.
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73.25.+i Surface conductivity and carrier phenomena
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.65.Rv Passivation
68.55.A- Nucleation and growth

Spin transport in germanium at room temperature

C. Shen, T. Trypiniotis, K. Y. Lee, S. N. Holmes, R. Mansell, M. Husain, V. Shah, X. V. Li, H. Kurebayashi, I. Farrer, C. H. de Groot, D. R. Leadley, G. Bell, E. H. C. Parker, T. Whall, et al.

Appl. Phys. Lett. 97, 162104 (2010); http://dx.doi.org/10.1063/1.3505337 (3 pages) | Cited 5 times

Online Publication Date: 20 October 2010

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Spin-dependent transport is investigated in a Ni/Ge/AlGaAs junction with an electrodeposited Ni contact. Spin-polarized electrons are excited by optical spin orientation and are subsequently used to measure the spin dependent conductance at the Ni/Ge Schottky interface. We demonstrate electron spin transport and electrical extraction from the Ge layer at room temperature.
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72.25.-b Spin polarized transport
73.30.+y Surface double layers, Schottky barriers, and work functions

Ti/Cu bilayer electrodes for SiNx-passivated Hf–In–Zn–O thin film transistors: Device performance and contact resistance

Joon Seok Park, Tae Sang Kim, Kyoung Seok Son, Eunha Lee, Ji Sim Jung, Kwang-Hee Lee, Wan-Joo Maeng, Hyun-Suk Kim, Eok Su Kim, Kyung-Bae Park, Jang-Yeon Kwon, Myung Kwan Ryu, and Sang Yoon Lee

Appl. Phys. Lett. 97, 162105 (2010); http://dx.doi.org/10.1063/1.3505151 (3 pages) | Cited 4 times

Online Publication Date: 21 October 2010

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In this study, we examine the possibility of using Ti/Cu bilayer as source/drain electrodes for SiNx-passivated Hf–In–Zn–O (HIZO) thin film transistors by comparing their electrical properties with devices that use Mo electrodes. The Mo devices operate in depletion mode with a higher field effect mobility, while the Ti/Cu devices exhibit an improved subthreshold swing and operate in enhancement mode. Transmission electron microscopy characterization reveals the formation of an amorphous TiOx layer at the Ti/HIZO interface, which is suggested to be responsible for the disparate device characteristics in terms of contact resistance and threshold delay.
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85.30.Tv Field effect devices
82.45.Fk Electrodes

Lateral confinement of electrons in vicinal N-polar AlGaN/GaN heterostructure

Digbijoy N. Nath, Stacia Keller, Eric Hsieh, Steven P. DenBaars, Umesh K. Mishra, and Siddharth Rajan

Appl. Phys. Lett. 97, 162106 (2010); http://dx.doi.org/10.1063/1.3505319 (3 pages) | Cited 2 times

Online Publication Date: 21 October 2010

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We studied orientation dependent transport in vicinal N-polar AlGaN/GaN heterostructures. We observed significant anisotropy in the current carrying charge parallel and perpendicular to the miscut direction. A quantitative estimate of the charge anisotropy was made based on gated transmission line measurement and Hall measurements. The formation of electrostatically confined one-dimensional channels is hypothesized to explain charge anisotropy. A mathematical model was used to verify that polarization charges distributed on miscut structure can create lateral one-dimensional confinement in vicinal substrates. This polarization-engineered electrostatic confinement observed is promising for new research on low-dimensional physics and devices besides providing a template for manufacturable one-dimensional devices.
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81.05.Ea III-V semiconductors
73.63.-b Electronic transport in nanoscale materials and structures
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.20.My Galvanomagnetic and other magnetotransport effects

Effect of germanium on the kinetics of boron-oxygen defect generation and dissociation in Czochralski silicon

Xuegong Yu, Peng Wang, and Deren Yang

Appl. Phys. Lett. 97, 162107 (2010); http://dx.doi.org/10.1063/1.3505499 (3 pages) | Cited 1 time

Online Publication Date: 21 October 2010

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We have investigated the kinetics of boron-oxygen (B–O) defect generation and dissociation in germanium-doped Czochralski (GCZ) silicon. It is found that the activation energies for the B–O defect generation and dissociation in the GCZ silicon are around 0.63 eV and 1.52 eV, respectively, both larger than those in the conventional CZ silicon. The corresponding pre-exponential factors also are enhanced by two orders of magnitude due to Ge doping. It is believed that the Ge cannot only cause a higher energy barrier for oxygen-dimer (O2i) diffusion, due to its modulation on the crystal field in silicon lattice but also enhance the capture cross-section of Bs for O2i, as a result of Ge–B complex formation, as predicted by first-principle calculation. These results are significant for us to understand the mechanism of Ge influencing on the B–O defects in CZ silicon.
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61.72.Cc Kinetics of defect formation and annealing
61.72.uf Ge and Si
61.72.jd Vacancies
71.70.Ch Crystal and ligand fields

Ultrashallow Ohmic contacts for n-type Ge by Sb δ-doping

K. Sawano, Y. Hoshi, K. Kasahara, K. Yamane, K. Hamaya, M. Miyao, and Y. Shiraki

Appl. Phys. Lett. 97, 162108 (2010); http://dx.doi.org/10.1063/1.3503587 (3 pages) | Cited 2 times

Online Publication Date: 21 October 2010

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We demonstrate ultrashallow Ohmic contacts for n-Ge by the Sb δ-doping and low-temperature Ge homoepitaxy. We find that the segregation effect of Sb on Ge(111) is lower than that on Ge(100) for growth temperatures below 400 °C. Consequently, we achieve the δ-doping for Ge(111), having very high concentrations above 1020 cm−3 and abrupt profiles within nanometer-scale widths. By introducing the δ-doping to atomically controlled metal/Ge Schottky contacts, completely symmetric current-voltage characteristics, that is, low-resistivity Ohmic contacts are obtained owing to the effective tunneling conduction through the Schottky barrier.
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73.40.Ns Metal-nonmetal contacts
73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Gk Tunneling
68.35.Dv Composition, segregation; defects and impurities

Band offsets determination and interfacial chemical properties of the Al2O3/GaSb system

I. Geppert, M. Eizenberg, A. Ali, and S. Datta

Appl. Phys. Lett. 97, 162109 (2010); http://dx.doi.org/10.1063/1.3499655 (3 pages) | Cited 4 times

Online Publication Date: 22 October 2010

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Band offsets of the Al2O3/GaSb system and various surface passivation treatments of the GaSb substrate by HCl, NH4OH, and (NH4)2S solutions were investigated by x-ray photoelectron spectroscopy. The extracted conduction and valence band offsets values of Al2O3 relative to GaSb are 2.4±0.1 eV and 3.4±0.2 eV, respectively. The presence of Ga–O and Sb–O bonds was detected after NH4OH surface treatment. In contrast, (NH4)2S and HCl solutions inhibit the Sb oxide formation. The lowest amount of Ga–O bands was obtained for (NH4)2S passivation. These results correlate with capacitance-voltage (C-V) measurements of Pd–Au/Al2O3/GaSb stacks which yielded the best characteristics for the S-based passivation.
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71.20.Ps Other inorganic compounds
81.65.Rv Passivation
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
79.60.Dp Adsorbed layers and thin films
79.60.Bm Clean metal, semiconductor, and insulator surfaces
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