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15 Apr 2012

Volume 111, Issue 8, Articles (08xxxx)

Issue Cover Spotlight Figure

J. Appl. Phys. 111, 084701 (2012); http://dx.doi.org/10.1063/1.3698319 (11 pages)

Xerxes Lopez-Yglesias, Jason M. Gamba, and Richard C. Flagan
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back to top Device Physics

Resistive switching behavior in diamond-like carbon films grown by pulsed laser deposition for resistance switching random access memory application

Pinggang Peng, Dan Xie, Yi Yang, Yongyuan Zang, Xili Gao, Changjian Zhou, Tingting Feng, He Tian, Tianling Ren, and Xiaozhong Zhang

J. Appl. Phys. 111, 084501 (2012); http://dx.doi.org/10.1063/1.3703063 (4 pages) | Cited 1 time

Online Publication Date: 16 April 2012

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In this paper, nonvolatile bipolar resistive memory effects were observed in nitrogen doped diamond-like carbon (DLC) thin films prepared by a pulsed laser deposition technique. It is observed that the fabricated Pt/Ti/DLC/Pt structure exhibits good memory performances with an ON/OFF ratio >10, data retention time >104 s, and low operation voltage (<1.5 V). The current mechanism is fitted by Ohmic and space charge limited conduction laws in low resistance state and high resistance state scenarios. The formation/rupture of metal filaments is due to the diffusion of the titanium ions.
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84.30.Sk Pulse and digital circuits
81.05.ug Diamond
81.15.Fg Pulsed laser ablation deposition

Hole shape effect induced optical response to permittivity change in palladium sub-wavelength hole arrays upon hydrogen exposure

Etsuo Maeda, Takanori Matsuki, Ichiro Yamada, and Jean-Jacques Delaunay

J. Appl. Phys. 111, 084502 (2012); http://dx.doi.org/10.1063/1.3703664 (6 pages)

Online Publication Date: 16 April 2012

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Sensing with sub-wavelength hole arrays is being actively researched as a means to improve detection sensitivity and reduce the size of the developed sensor. One of the approaches to sensing with hole arrays is to use a shift of the main transmittance peak generated by analyte exposure. In this report, the effect of the shape of the holes on the peak shift is investigated with a view to improve further the main transmittance peak shift. Rectangular holes are studied by simulation and experiments with a palladium metallic matrix. Palladium permittivity is varied by exposure to hydrogen and generates main transmittance peak shifts toward longer wavelengths. The simulation results of the propagation constant and electric field distribution revealed that the peak shift is controlled by the short side length of the rectangular holes. The short side of the rectangular holes normalized by the peak wavelength should be below 1/10 for the rectangular holes to achieve their maximum effect.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
42.79.Pw Imaging detectors and sensors

Effects of high temperature annealing on single crystal ZnO and ZnO devices

W. Mtangi, F. D. Auret, M. Diale, W. E. Meyer, A. Chawanda, H. de Meyer, P. J. Janse van Rensburg, and J. M. Nel

J. Appl. Phys. 111, 084503 (2012); http://dx.doi.org/10.1063/1.3700186 (6 pages) | Cited 2 times

Online Publication Date: 16 April 2012

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We have systematically investigated the effects of high-temperature annealing on ZnO and ZnO devices using current voltage, deep level transient spectroscopy (DLTS) and Laplace DLTS measurements. Current–voltage measurements reveal the decrease in the quality of devices fabricated on the annealed samples, with the high-temperature annealed samples yielding devices with low barrier heights and high reverse currents. DLTS results indicate the presence of three prominent defects in the as-received samples. Annealing the ZnO samples at 300 °C, 500 °C, and 600 °C in Ar results in an increase in reverse leakage current of the Schottky contacts and an introduction of a new broad peak. After 700 °C annealing, the broad peak is no longer present, but a new defect with an activation enthalpy of 0.18 eV is observed. Further annealing of the samples in oxygen after Ar annealing causes an increase in intensity of the broad peak. High-resolution Laplace DLTS has been successfully employed to resolve the closely spaced energy levels.
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85.30.-z Semiconductor devices

Non-localized trapping effects in AlGaN/GaN heterojunction field-effect transistors subjected to on-state bias stress

Cheng-Yu Hu (胡成余) and Tamotsu Hashizume (橋詰保)

J. Appl. Phys. 111, 084504 (2012); http://dx.doi.org/10.1063/1.4704393 (9 pages)

Online Publication Date: 19 April 2012

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For AlGaN/GaN heterojunction field-effect transistors, on-state-bias-stress (on-stress)-induced trapping effects were observed across the entire drain access region, not only at the gate edge. However, during the application of on-stress, the highest electric field was only localized at the drain side of the gate edge. Using the location of the highest electric field as a reference, the trapping effects at the gate edge and at the more distant access region were referred to as localized and non-localized trapping effect, respectively. Using two-dimensional-electron-gas sensing-bar (2DEG-sensing-bar) and dual-gate structures, the non-localized trapping effects were investigated and the trap density was measured to be ∼1.3 × 1012 cm−2. The effect of passivation was also discussed. It was found that both surface leakage currents and hot electrons are responsible for the non-localized trapping effects with hot electrons having the dominant effect. Since hot electrons are generated from the 2DEG channel, it is highly likely that the involved traps are mainly in the GaN buffer layer. Using monochromatic irradiation (1.24–2.81 eV), the trap levels responsible for the non-localized trapping effects were found to be located at 0.6–1.6 eV from the valence band of GaN. Both trap-assisted impact ionization and direct channel electron injection are proposed as the possible mechanisms of the hot-electron-related non-localized trapping effect. Finally, using the 2DEG-sensing-bar structure, we directly confirmed that blocking gate injected electrons is an important mechanism of Al2O3 passivation.
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85.30.Tv Field effect devices
81.65.Rv Passivation

Photovoltaic infrared detection with p-type graded barrier heterostructures

P. K. D. D. P. Pitigala, S. G. Matsik, A. G. U. Perera, S. P. Khanna, L. H. Li, E. H. Linfield, Z. R. Wasilewski, M. Buchanan, and H. C. Liu

J. Appl. Phys. 111, 084505 (2012); http://dx.doi.org/10.1063/1.4704695 (5 pages)

Online Publication Date: 19 April 2012

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Photovoltaic infrared detectors have significant advantages over photoconductive detectors due to zero bias operation, requiring low power and having reduced low frequency noise. They also exhibit no thermally assisted tunneling currents, leading to higher operating temperatures. p-type emitter/graded barrier GaAs/AlxGa1−xAs structures were tested as photovoltaic detectors in the infrared region, operating under uncooled conditions and without an applied bias voltage. A photovoltaic responsivity of 450 mV/W was obtained with a detectivity (D*) of 1.2 × 106 Jones at a peak wavelength 1.8 μm at 300 K. Responsivity and D* increased to ∼1.2 V/W and 2.8 × 106 Jones, respectively, at 280 K. A non-linear improvement in responsivity was observed with increased emitter thickness.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

Electromagnetic responses of magnetic conductive hollow fibers

Lianwen Deng, Heng Luo, Shengxiang Huang, Liang Zhou, Zhaowen Hu, Kesheng Zhou, and Peng Xiao

J. Appl. Phys. 111, 084506 (2012); http://dx.doi.org/10.1063/1.3702878 (8 pages)

Online Publication Date: 23 April 2012

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Electromagnetic parameters for a magnetic conductive hallow fiber have been derived, and the anisotropy of the magnetic permeability and the electric permittivity for a hollow fiber was demonstrated theoretically. The axial parameters μ// and ɛ// are the key factors related to electromagnetic characteristics of the hollow fiber. Simulations have been carried out to study the axial permeability μ//, and axial permittivity ɛ// of a magnetic conductive hallow fiber with different geometric, and electrical parameters such as diameter, aspect ratio and conductivity The simulations carried out reveal several interesting properties of the hallow fiber’s electromagnetic parameters. (1) The parameters μ′//, μ″//, ɛ′// and ɛ″// all decrease with increasing outer radius from 0.5 to 6 µm. (2) When the aspect ratio of the hallow fiber is above 30 µm, μ′// and μ″// remain at constant, while, ɛ′// and ɛ″// are found to increase. (3) The parameters μ′//, μ″//, and ɛ′// all decrease with increasing conductivity, however ɛ″// increases with increasing conductivity. Additionally these simulated results are consistent with reported experimental results carried out on electromagnetically modified hollow carbon fibers.
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77.22.Ch Permittivity (dielectric function)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy
72.80.-r Conductivity of specific materials
02.30.Rz Integral equations
02.60.Nm Integral and integrodifferential equations

Photovoltaic properties of the p-CuO/n-Si heterojunction prepared through reactive magnetron sputtering

Fei Gao, Xiao-Jing Liu, Jun-Shan Zhang, Mei-Zhou Song, and Ning Li

J. Appl. Phys. 111, 084507 (2012); http://dx.doi.org/10.1063/1.4704382 (4 pages)

Online Publication Date: 23 April 2012

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Films of p-CuO were deposited on glass and n-Si substrates through reactive magnetron sputtering. The influence of flow rate ratio of O2 to Ar on the structural and electrical properties of the CuO films was studied. By increasing the flow rate ratio, the hole concentration of the CuO films decreased while the mobility and resistivity increase. At a flow rate ratio of 0.5, the average crystal size, hole concentration, mobility, resistivity, and optical bandgap of the deposited p-CuO films are ∼8 nm, 2.76×1015 cm−3, 0.134 cm2/Vs, 0.217 Ωcm, and 1.07 eV, respectively. A p-CuO film/n-Si substrate heterojunction cell has been fabricated and has an open-circuit voltage of 0.33 V and short-circuit current density of 6.27 mA/cm2 under AM 1.5D illumination. The fill factor and energy conversion efficiency are 0.2 and 0.41%, respectively.
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72.40.+w Photoconduction and photovoltaic effects
81.15.Cd Deposition by sputtering
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
68.55.-a Thin film structure and morphology
73.61.Cw Elemental semiconductors

Relaxation dynamics of ionic liquid—VO2 interfaces and influence in electric double-layer transistors

You Zhou and Shriram Ramanathan

J. Appl. Phys. 111, 084508 (2012); http://dx.doi.org/10.1063/1.4704689 (7 pages) | Cited 1 time

Online Publication Date: 23 April 2012

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Oxide semiconductor systems are often electrostatically doped with ionic liquids as gate insulators towards modulating carrier density and inducing phase transitions, while simultaneously serving as a means to probe their electronic phase diagram. The electronic and electrochemical properties of ionic liquid/correlated oxide interfaces are, therefore, important in interpreting such field-effect phenomena. Here, we use DEME-TFSI and VO2 as a model system to investigate the interface properties, slow relaxations, as well as field-effect in electric double layer transistor geometry. The stability of these interfaces is probed by combination of current-voltage measurements, x-ray photoelectron spectroscopy, impedance spectroscopy, and constant current charging. Three-terminal field effect transistor-type devices fabricated by photolithography are used to investigate kinetics of channel resistance modulations under varying gate bias polarity. Bias regions for reversible modulation of channel conductance have been determined. A time-dependent transconductance effect and as large as 20× increase in conductance are observed.
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85.30.Tv Field effect devices
85.40.Hp Lithography, masks and pattern transfer
85.40.Ry Impurity doping, diffusion and ion implantation technology

A low-voltage high-speed electronic switch based on piezoelectric transduction

Dennis Newns, Bruce Elmegreen, Xiao Hu Liu, and Glenn Martyna

J. Appl. Phys. 111, 084509 (2012); http://dx.doi.org/10.1063/1.4704391 (18 pages)

Online Publication Date: 24 April 2012

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We propose a novel digital switch, the piezoelectronic transistor or PET. Based on properties of known materials, we predict that a nanometer-scale PET can operate at low voltages and relatively high speeds, exceeding the capabilities of any conventional field effect transistor (FET). Depending on the degree to which these attributes can be simultaneously achieved, the device has a broad array of potential applications in digital logic. The PET is a 3-terminal switch in which a gate voltage is applied to a piezoelectric (PE), resulting in expansion compressing a piezoresistive (PR) material comprising the channel, which then undergoes a continuous, reversible insulator-metal transition. The channel becomes conducting in response to the gate voltage. A high piezoelectric coefficient PE, e.g., a relaxor piezoelectric, leads to low voltage operation. Suitable channel materials manifesting a pressure-induced metal-insulator transition can be found amongst rare earth chalcogenides, transition metal oxides, and among others. Mechanical requirements include a high PE/PR area ratio to step up pressure, a rigid surround material to constrain the PE and PR external boundaries normal to the strain axis, and a void space to enable free motion of the component side walls. Using static mechanical modeling and dynamic electro-acoustic simulations, we optimize device structure and materials and predict performance.
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89.20.Kk Engineering
84.32.Ff Conductors, resistors (including thermistors, varistors, and photoresistors)
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

The systematic study and simulation modeling on nano-level dislocation edge stress effects

M.-H. Liao, C.-H. Chen, L.-C. Chang, and C. Yang

J. Appl. Phys. 111, 084510 (2012); http://dx.doi.org/10.1063/1.4706565 (4 pages)

Online Publication Date: 27 April 2012

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The comprehensive investigation on the effect of dislocation edge stress for Si N-type metal-oxide-semiconductor field-effect transistors is presented in this work by the experimental measurement and proposed simulation model. The accurate stress measurement in Si OD region with and without dislocation edge stress treatment is extracted by atomic force microscope-Raman technique with the nanometer level space resolution. Less compressive stress in Si OD region on the real transistor with dislocation edge stress treatment is observed successfully and has its corresponding higher electron carrier mobility, agreed with the strained Si theory. Main reasons for the less compressive stress in the device with dislocation edge stress treatment are the more stress relaxation of the STI intrinsic compressive stress in modern CMOS process and one layer Si atom missing near the source and drain region along the dislocation line. The measured stress from AFM-Raman spectra experimentally, the simulated stress from proposed finite element method, and its corresponding electrical characteristics agrees well with each other in this work. After the comprehensive understanding and calibrated model for the dislocation edge stress, the relationship between channel stress and dislocation edge shapes, including the angle and length of dislocation lines is simulated and investigated clearly. It can be found that longer dislocation line and smaller dislocation angle can relax the intrinsic STI compressive stress more and should have the better electron carrier mobility and device performance for N-MOSFETs.
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85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling

Monte Carlo studies of the intrinsic time-domain response of nanoscale three-branch junctions

I. Iñiguez-de-la-Torre, H. Rodilla, J. Mateos, T. González, H. Irie, and Roman Sobolewski

J. Appl. Phys. 111, 084511 (2012); http://dx.doi.org/10.1063/1.4704371 (4 pages)

Online Publication Date: 27 April 2012

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We present a Monte Carlo time-domain study of nanostructured ballistic three-branch junctions (TBJs) excited by both step-function and Gaussian picosecond transients. Our TBJs were based on InGaAs 2-dimensional electron gas heterostructures and their geometry followed exactly the earlier experimental studies. Time-resolved, picosecond transients of both the central branch potential and the between-the-arms current demonstrate that the bandwidth of the intrinsic TBJ response reaches the THz frequency range, being mainly limited by the large-signal, intervalley scattering, when the carrier transport regime changes from ballistic to diffusive.
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73.23.Ad Ballistic transport
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Optimization of resistive switching performance of metal-manganite oxide interfaces by a multipulse protocol

N. Ghenzi, M. J. Sánchez, M. J. Rozenberg, P. Stoliar, F. G. Marlasca, D. Rubi, and P. Levy

J. Appl. Phys. 111, 084512 (2012); http://dx.doi.org/10.1063/1.4705283 (5 pages)

Online Publication Date: 30 April 2012

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We explore different resistance states of La0.325Pr0.300Ca0.375MnO3-Ti interfaces as prototypes of non-volatile memory devices at room temperature. In addition to high and low resistance states accessible through bipolar pulsing with one pulse, higher resistance states can be obtained by repeatedly pulsing with a single polarity. The accumulative action of successive pulsing drives the resistance towards saturation, the time constant being a strong function of the pulsing amplitude. The experiments reveal that the pulsing amplitude and the number of applied pulses necessary to reach a target high resistance value appear to be in an exponential relationship, with a rate that results independent of the resistance value. Model simulations confirm these results and provide the oxygen vacancy profiles associated to the high resistance states obtained in the experiments.
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84.30.Sk Pulse and digital circuits
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