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9 Jun 2008

Volume 92, Issue 23, Articles (23xxxx)

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Appl. Phys. Lett. 92, 231901 (2008); http://dx.doi.org/10.1063/1.2938921 (3 pages)

N. A. Mara, D. Bhattacharyya, P. Dickerson, R. G. Hoagland, and A. Misra
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Spin injection from Co2MnGa into an InGaAs quantum well

M. C. Hickey, C. D. Damsgaard, S. N. Holmes, I. Farrer, G. A. C. Jones, D. A. Ritchie, C. S. Jacobsen, J. B. Hansen, and M. Pepper

Appl. Phys. Lett. 92, 232101 (2008); http://dx.doi.org/10.1063/1.2938418 (3 pages) | Cited 9 times

Online Publication Date: 9 June 2008

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We have demonstrated spin injection from a full Heusler alloy Co2MnGa thin film into a (100) InGaAs quantum well in a semiconductor light-emitting diode structure at a temperature of 5 K. The detection is performed in the oblique Hanle geometry, allowing quantification of the effective spin lifetime and spin detection efficiency (22±4%). This work builds on existing studies on off-stoichiometric Heusler injectors into similar light-emitting-diode structures. The role of injector stoichiometry can therefore be quantitatively assessed with the result that the spin injection efficiency increases by a factor of approximately 2 as compared with an off-stoichiometric Co2.4Mn1.6Ga injector.
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73.63.Hs Quantum wells
72.25.Dc Spin polarized transport in semiconductors

CO2 detection using polyethylenimine/starch functionalized AlGaN/GaN high electron mobility transistors

C. Y. Chang, B. S. Kang, H. T. Wang, F. Ren, Y. L. Wang, S. J. Pearton, D. M. Dennis, J. W. Johnson, P. Rajagopal, J. C. Roberts, E. L. Piner, and K. J. Linthicum

Appl. Phys. Lett. 92, 232102 (2008); http://dx.doi.org/10.1063/1.2937126 (3 pages) | Cited 10 times

Online Publication Date: 10 June 2008

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AlGaN/GaN high electron mobility transistors (HEMTs) functionalized with polyethylenimine/starch were used for detecting CO2 with a wide dynamic range of 0.9%–50% balanced with nitrogen at temperatures from 46 to 220 °C. Higher detection sensitivity to CO2 gas was achieved at higher testing temperatures. At a fixed source-drain bias voltage of 0.5 V, drain-source current of the functionalized HEMTs showed a sublinear correlation upon exposure to different CO2 concentrations at low temperature. The superlinear relationship was at high temperature. The sensor exhibited a reversible behavior and a repeatable current change of 32 and 47 μA with the introduction of 28.57% and 37.5% CO2 at 108 °C, respectively.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
85.30.Tv Field effect devices

Complementary inverter circuits based on p-SnO2 and n-In2O3 thin film transistors

Dhananjay, Chih-Wei Chu, Chun-Wei Ou, Meng-Chyi Wu, Zhong-Yo Ho, Kuo-Chuan Ho, and Shih-Wei Lee

Appl. Phys. Lett. 92, 232103 (2008); http://dx.doi.org/10.1063/1.2936275 (3 pages) | Cited 9 times

Online Publication Date: 11 June 2008

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Thin film transistors (TFTs) of indium oxide (In2O3) and tin oxide (SnO2) were fabricated on SiO2 gate dielectric using reactive evaporation process. Structural investigation of the films revealed that In2O3 films were polycrystalline in nature with preferred (222) orientation and SnO2 films exhibited amorphous nature. The x-ray photoelectric spectroscopy measurements suggest that SnO2 films were oxygen rich and presume mixed oxidation states of Sn, namely Sn2+ and Sn4+. While the In2O3 based TFTs possess n-type channel conduction, SnO2 based TFTs exhibited anomalous p-type conductivity. Integration of these n- and p-type devices resulted in complementary inverter with a gain of 11.
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84.30.Jc Power electronics; power supply circuits
85.30.Tv Field effect devices

Semiconductor charge transport driven by a picosecond strain pulse

D. R. Fowler, A. V. Akimov, A. G. Balanov, M. T. Greenaway, M. Henini, T. M. Fromhold, and A. J. Kent

Appl. Phys. Lett. 92, 232104 (2008); http://dx.doi.org/10.1063/1.2942389 (3 pages) | Cited 1 time

Online Publication Date: 11 June 2008

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We demonstrate that a picosecond strain pulse can be used to drive an electric current through both thin-film epilayer and heterostructure semiconductor crystals in the absence of an external electric field. By measuring the transient current pulses, we are able to clearly distinguish the effects of the coherent and incoherent components of the acoustic packet. The properties of the strain induced signal suggest a technique for exciting picosecond current pulses, which may be used to probe semiconductor devices.
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73.61.-r Electrical properties of specific thin films
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Postgrowth annealing of GaInAs/GaAs and GaInAsN/GaAs quantum well samples placed in a proximity GaAs box: A simple method to improve the crystalline quality

J. Pakarinen, C. S. Peng, J. Puustinen, P. Laukkanen, V.-M. Korpijärvi, A. Tukiainen, and M. Pessa

Appl. Phys. Lett. 92, 232105 (2008); http://dx.doi.org/10.1063/1.2943157 (3 pages) | Cited 11 times

Online Publication Date: 11 June 2008

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The effects of thermal annealing on GaInAs/GaAs and GaInAsN/GaAs quantum wells, grown by molecular beam epitaxy, were investigated. Optical and structural properties were examined upon annealing when the samples had a 200 nm thick SiO2 cap layer, or were placed in a so-called GaAs box or were left uncapped. The GaAs box gave rise to the strongest photoluminescence without significant blueshift or structural changes at moderate annealing temperature. Capping with SiO2 impaired the samples and caused a more pronounced blueshift for the GaInAs quantum wells than for the GaInAsN ones. These results consolidate our understanding of the blueshift mechanisms.
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81.05.Ea III-V semiconductors
81.07.St Quantum wells
78.67.De Quantum wells
73.63.Hs Quantum wells
61.72.Cc Kinetics of defect formation and annealing
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Broadband electrical detection of spin excitations in Ga0.98Mn0.02As using a photovoltage technique

André Wirthmann, Xiong Hui, N. Mecking, Y. S. Gui, T. Chakraborty, C.-M. Hu, M. Reinwald, C. Schüller, and W. Wegscheider

Appl. Phys. Lett. 92, 232106 (2008); http://dx.doi.org/10.1063/1.2943280 (3 pages) | Cited 4 times

Online Publication Date: 11 June 2008

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We report on microwave photovoltage and simultaneous magnetotransport measurements in a (Ga, Mn) As film oriented normal to the magnetic field. We detect the ferromagnetic resonance over a broad frequency range of 2–18.5 GHz and determine the spectroscopic g-factor and separate the Gilbert from the inhomogeneous contribution to magnetization relaxation. Temperature dependent measurements below the saturation magnetization indicate that the photovoltage signal can serve as a sensitive tool to study the crystal anisotropy. We demonstrate that the combination of spin dynamics with charge transport is a promising tool to study microstructured ferromagnetic semiconductor samples.
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75.70.Ak Magnetic properties of monolayers and thin films
73.50.Pz Photoconduction and photovoltaic effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.50.Dd Nonmetallic ferromagnetic materials

Temporary transition in suspended carbon nanotubes

Sen-Hong Syue, Hsin-Fu Kuo, Ching-Tung Hsu, Hung-Jen Chen, Uei-Shin Chen, Wen-Kuang Hsu, and Han-Chang Shih

Appl. Phys. Lett. 92, 232107 (2008); http://dx.doi.org/10.1063/1.2943321 (3 pages) | Cited 2 times

Online Publication Date: 11 June 2008

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A semiconducting phase is temporarily present in doped carbon nanotube after field treatment and underlying mechanism involves chemical potential change and EF movement by field induced charge accumulation. Metallic phase re-emerges as accumulated charges are released.
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73.63.Fg Nanotubes
73.61.Cw Elemental semiconductors
61.46.Fg Nanotubes
61.48.De Structure of carbon nanotubes, boron nanotubes, and other related systems
82.60.-s Chemical thermodynamics

Hard x-ray photoemission spectroscopy in wurtzite-type zinc magnesium oxide solid-solution films grown by pulsed-laser deposition

Takeo Ohsawa, Naoki Ohashi, Yutaka Adachi, Isao Sakaguchi, Haruki Ryoken, Kenji Matsumoto, Hajime Haneda, Shigenori Ueda, Hideki Yoshikawa, and Keisuke Kobayashi

Appl. Phys. Lett. 92, 232108 (2008); http://dx.doi.org/10.1063/1.2942393 (3 pages) | Cited 6 times

Online Publication Date: 12 June 2008

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The electronic structure of Zn1−xMgxO alloy thin films was determined by hard x-ray photoemission spectroscopy (HX-PES) and optical transmittance measurements. HX-PES measurements revealed that the binding energies of valence band, Zn 2p, and O 1s levels increased with increasing MgO fraction. The energy shift correlated with a widening of the band gap and change in ionicity of chemical bonds by alloying. The Fermi level in the alloy compounds was found to be close to the bottom of conduction band regardless of the MgO fraction.
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71.20.Nr Semiconductor compounds
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Hf II-VI semiconductors
68.55.-a Thin film structure and morphology
81.15.Fg Pulsed laser ablation deposition
79.60.Dp Adsorbed layers and thin films

Current-voltage characteristics of phase separated La0.5Ca0.5MnO3/Nb–SrTiO3 p-n junction and magnetic tunability

B. T. Xie, Y. G. Zhao, C. M. Xiong, S. Park, and Weida Wu

Appl. Phys. Lett. 92, 232109 (2008); http://dx.doi.org/10.1063/1.2944261 (3 pages) | Cited 4 times

Online Publication Date: 12 June 2008

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The authors report the current-voltage characteristics of La0.5Ca0.5MnO3/Nb-SrTiO3 p-n junction. This junction shows remarkable thermal hysteresis, giant negative magnetoresistance (MR), remarkable differences of MR for the zero field cooling and field cooling processes, and memory effect of magnetic field. Magnetic force microscopy studies provide direct evidence of magnetic inhomogeneity in La0.5Ca0.5MnO3 film. These intriguing behaviors of our p-n junction can be explained by the phase separation in La0.5Ca0.5MnO3. This work demonstrates the principle of harnessing phase separation for highly tunable device applications.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
75.47.De Giant magnetoresistance
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
73.43.Qt Magnetoresistance
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)

Dopant-stress synergy in Si solid-phase epitaxy

N. G. Rudawski, K. S. Jones, and R. Gwilliam

Appl. Phys. Lett. 92, 232110 (2008); http://dx.doi.org/10.1063/1.2945291 (3 pages) | Cited 10 times

Online Publication Date: 12 June 2008

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The influence of dopants on stressed solid-phase epitaxy of Si was studied in B-doped material up to B concentration of ∼ 3.0×1020 cm−3 and stress of 1.0±0.1 GPa. As per the generalized Fermi level shifting model of growth enhancement in the presence of electrically active impurities, it is advanced that application of compressive stress may increase the energy difference between intrinsic Fermi and acceptor levels thus making dopant and stress effects synergistic in growth kinetics.
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61.72.uf Ge and Si
71.55.Cn Elemental semiconductors
81.15.Np Solid phase epitaxy; growth from solid phases
68.55.ag Semiconductors
61.72.sd Impurity concentration

Vertical structure p-type permeable metal-base organic transistors based on N,N′-diphentyl-N,N′-bis(1-naphthylphenyl)-1,1′-biphenyl-4,4′-diamine

Jinying Huang, Mingdong Yi, Dongge Ma, and Ivo A. Hümmelgen

Appl. Phys. Lett. 92, 232111 (2008); http://dx.doi.org/10.1063/1.2944880 (3 pages) | Cited 6 times

Online Publication Date: 12 June 2008

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In this article, vertical structure p-type permeable-base organic transistors were proposed and demonstrated. A hole-type organic semiconductor N,N′-diphentyl-N,N′-bis(1-naphthylphenyl)-1,1′-biphenyl-4,4′-diamine was used as emitter and collector. In the permeable-base transistors, the metal base was formed by firstly coevaporating Al and Ca in vacuum and then annealing at 120 °C for 5 min in air, followed by a thin Al deposition. These devices show a common-base current gain of near 1.0 and a common-emitter current gain of ∼ 270.
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85.30.Pq Bipolar transistors
85.30.Tv Field effect devices
72.80.Le Polymers; organic compounds (including organic semiconductors)
61.72.Cc Kinetics of defect formation and annealing

Characteristics and mechanism of conduction/set process in TiN/ZnO/Pt resistance switching random-access memories

Nuo Xu, Lifeng Liu, Xiao Sun, Xiaoyan Liu, Dedong Han, Yi Wang, Ruqi Han, Jinfeng Kang, and Bin Yu

Appl. Phys. Lett. 92, 232112 (2008); http://dx.doi.org/10.1063/1.2945278 (3 pages) | Cited 64 times

Online Publication Date: 13 June 2008

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The characteristics and mechanism of conduction/set process in TiN/ZnO/Pt-based resistance random access memory devices with stable and reproducible nanosecond bipolar switching behavior were studied. The dependencies of memory behavior on cell area, operating temperature, and frequency indicate that the conduction mechanism in low-resistance states is due to electrons hopping through filament paths. We also identify that the set process is essentially equivalent to a soft dielectric breakdown associated with a polarization effect caused by the migration of space charges under a low electric field stress. The generation/recovery of oxygen vacancies and nonlattice oxygen ions play a critical role in resistance switching.
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84.30.Sk Pulse and digital circuits
77.22.Jp Dielectric breakdown and space-charge effects
77.22.Ej Polarization and depolarization
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