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31 Jul 2000

Volume 77, Issue 5, pp. 609-762

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Underwater shock measurements using a ruby pressure gauge

G. I. Pangilinan, T. P. Russell, M. R. Baer, J. Namkung, and P. Chambers

Appl. Phys. Lett. 77, 684 (2000); http://dx.doi.org/10.1063/1.127085 (3 pages)

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The measurement of the temporal profile of the pressure in a shock wave propagating underwater and interacting with a nearby metal plate is presented. Pressures are deduced from the time-resolved fluorescence of a submillimeter ruby crystal mounted on an optical fiber tip. The measured pressures agree with finite-element code predictions, which model the production and propagation of the shock wave. These measurements are useful to evaluate shock-induced phenomena that are strongly dependent on the temporal profile of a shock wave, in small-scale testing, and in substantiating finite-element code predictions. © 2000 American Institute of Physics.
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43.30.Xm Underwater measurement and calibration instrumentation and procedures
07.07.Mp Transducers
47.40.Nm Shock wave interactions and shock effects
78.55.Hx Other solid inorganic materials
43.30.Lz Underwater applications of nonlinear acoustics; explosions
62.50.-p High-pressure effects in solids and liquids
78.47.-p Spectroscopy of solid state dynamics
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X-ray photoelectron spectroscopy study of (NH4)2Sx-treated Mg-doped GaN layers

Yow-Jon Lin, Chang-Da Tsai, Yen-Tang Lyu, and Ching-Ting Lee

Appl. Phys. Lett. 77, 687 (2000); http://dx.doi.org/10.1063/1.127086 (3 pages) | Cited 21 times

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We present here the passivation mechanism and the chemistry of an (NH4)2Sx-treated Mg-doped GaN surface examined by using x-ray photoelectron spectroscopy. The native oxide on the GaN surface can be removed by the (NH4)2Sx treatment process. The S atoms not only bond as elemental sulfur and disulfides, but occupy nitrogen-related vacancies. © 2000 American Institute of Physics.
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81.05.Ea III-V semiconductors
81.65.Rv Passivation
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
61.72.Yx Interaction between different crystal defects; gettering effect

Identification of vacancy charge states in diffusion of arsenic in germanium

E. Vainonen-Ahlgren, T. Ahlgren, J. Likonen, S. Lehto, J. Keinonen, W. Li, and J. Haapamaa

Appl. Phys. Lett. 77, 690 (2000); http://dx.doi.org/10.1063/1.127087 (3 pages) | Cited 9 times

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Diffusion of As into Ge from a GaAs overlayer deposited on p-type Ge substrates has been studied by means of secondary ion mass spectrometry. A concentration-dependent diffusion of As atoms was observed in addition to the concentration-independent diffusion of Ga and As atoms. The concentration dependence is explained by a Fermi-level-dependent diffusion model. Arsenic atoms are shown to diffuse through Ge vacancies with the charge states 2− and 0. No presence of the singly negatively charged vacancies was observed, indicating that Ge vacancy could be a negative U center. © 2000 American Institute of Physics.
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66.30.J- Diffusion of impurities
71.55.Cn Elemental semiconductors
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
61.72.J- Point defects and defect clusters

The current–voltage dependence of nominally undoped thin conjugated polymer films

José A. Freire, M. G. E. da Luz, Dongge Ma, and I. A. Hümmelgen

Appl. Phys. Lett. 77, 693 (2000); http://dx.doi.org/10.1063/1.127088 (3 pages) | Cited 3 times

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The charge transport in conjugated polymer films sandwiched between metallic electrodes is described by means of a one-dimensional master equation where the hopping rates are given by thermally activated jumps over barriers separating trapping sites of same energy. An applied electric field along the chain reduces the barrier height leading to a field-dependent mobility, μ(E) ∼  sinh(E)/E. We exactly derive the current–voltage characteristics of such a system assuming that the injected carriers generate space charge effects inside the polymer. We find an excellent agreement with the experimental data for different types of conjugated materials and compare our model with other models that predict exp(math) for the field dependence of the mobility, discussing the essential differences between them. © 2000 American Institute of Physics.
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73.61.Ph Polymers; organic compounds
73.40.Sx Metal-semiconductor-metal structures
73.50.Fq High-field and nonlinear effects
73.50.Dn Low-field transport and mobility; piezoresistance
72.80.Le Polymers; organic compounds (including organic semiconductors)

Investigation of deep levels in rapid thermally annealed SiO2-capped n-GaAs grown by metal-organic chemical vapor deposition

P. N. K. Deenapanray, H. H. Tan, C. Jagadish, and F. D. Auret

Appl. Phys. Lett. 77, 696 (2000); http://dx.doi.org/10.1063/1.127089 (3 pages) | Cited 11 times

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Defects created in rapid thermally annealed (RTA) SiO2-capped epitaxial GaAs layers grown by metal-organic chemical vapor deposition have been investigated by deep level transient spectroscopy. RTA introduced four electron traps S1 (Ec−0.23 eV), S2 (Ec−0.46 eV), S3 (Ec−0.72 eV), and S4 (Ec−0.74 eV). S1 may be the so-called EL9 defect. We propose that S2 is a defect complex involving the Ga vacancy and Si dopant atoms, VGa–SiGa, and associate it with the EL5. S2 is introduced almost uniformly within the first 0.8 μm below the surface with an activation energy of 4.4 eV. S4 is most probably one of the EL2 family. The concentration of S4 decreased exponentially below the surface with a characteristic decay length ∼0.2 μm. The activation energy for the introduction of S4 is 2.5 eV. © 2000 American Institute of Physics.
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71.55.Eq III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Cc Kinetics of defect formation and annealing
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
66.30.Ny Chemical interdiffusion; diffusion barriers
81.05.Ea III-V semiconductors

Luminescence spectroscopy of GaN in the high-temperature regime from room temperature to 900 °C

A. P. Young and L. J. Brillson

Appl. Phys. Lett. 77, 699 (2000); http://dx.doi.org/10.1063/1.127090 (3 pages) | Cited 12 times

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We have measured the optical luminescence spectrum of GaN from the near infrared to the near ultraviolet at elevated temperatures. Despite intense blackbody radiation above 600 °C, luminescence is observable at 3 eV or greater at temperatures as high as 900 °C, i.e., including near-band-edge emissions over the entire range of GaN growth temperatures. Elevated-temperature measurements also reveal thermally activated quenching of the midgap “yellow” defect luminescence. These results show that electron beams already used to monitor molecular-beam epitaxy growth can also provide temperature and defect information during the growth process. © 2000 American Institute of Physics.
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78.60.Hk Cathodoluminescence, ionoluminescence
78.66.Fd III-V semiconductors
71.55.Eq III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
81.05.Ea III-V semiconductors

Observation of EL2 and additional deep levels at low temperature in an AlGaAs/GaAs multiple-quantum-well structure

Y. F. Zhang, Q. Zhuo, M. H. Zhang, Q. Huang, and J. M. Zhou

Appl. Phys. Lett. 77, 702 (2000); http://dx.doi.org/10.1063/1.127091 (3 pages) | Cited 1 time

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Using a YAG:Nd laser as a pump source, the properties of electroabsorption in Stark geometry AlGaAs/GaAs multiple-quantum-well a photorefractive structure are studied at low temperature. When the temperature decreases from 160 to 120 K, the electroabsorption demonstrates the characteristics of both quenchable and unquenchable components. The quenchable component is interpreted as the photoquenching of EL2, and the unquenchable component is ascribed to the existence of additional deep levels. Modulated with an equivalent circuit, the concentrations of these defects are predicted on the order of 1.3×1016 and 2.2×1018 cm−3, and the capture cross section of additional deep levels is about 4.5×10−16 cm2. The investigation of optical transient current spectra verifies our deduction. © 2000 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.55.Eq III-V semiconductors
78.20.Jq Electro-optical effects
78.66.Fd III-V semiconductors
73.20.Hb Impurity and defect levels; energy states of adsorbed species

Thermoelectric power factor in superlattice systems

D. A. Broido and T. L. Reinecke

Appl. Phys. Lett. 77, 705 (2000); http://dx.doi.org/10.1063/1.127092 (3 pages) | Cited 7 times

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A formalism is given for the power factor for thermoelectric transport in quantum well and wire superlattices using full electronic band structure and the complete inelastic Boltzmann equations for carrier-phonon scattering. Detailed calculations are given for realistic PbTe quantum well and quantum wire superlattices. In the quantum well case the dependence of the power factor on potential is much weaker than in previous work, and its behavior is traced to the underlying physics. Results are also given for the dependence of the power factors on growth direction. © 2000 American Institute of Physics.
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73.50.Lw Thermoelectric effects
73.61.Le Other inorganic semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
63.20.K- Phonon interactions
71.38.-k Polarons and electron-phonon interactions

Current-voltage curves of gold quantum point contacts revisited

K. Hansen, S. K. Nielsen, M. Brandbyge, E. Lægsgaard, I. Stensgaard, and F. Besenbacher

Appl. Phys. Lett. 77, 708 (2000); http://dx.doi.org/10.1063/1.127093 (3 pages) | Cited 61 times

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We present measurements of current–voltage (I–V) curves on gold quantum point contacts (QPCs) with a conductance up to 4 G0 (G0 = 2e2/h is the conductance quantum) and voltages up to 2 V. The QPCs are formed between the gold tip of a scanning tunneling microscope and a Au(110) surface under clean ultra-high-vacuum conditions at room temperature. The I–V curves are found to be almost linear in contrast to previous reports. Tight-binding calculations of I–V curves for one- and two-atom contacts are in excellent agreement with our measurements. On the other hand, clearly nonlinear I–V curves are only observed when the sample has been cleaned in air. © 2000 American Institute of Physics.
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73.40.Jn Metal-to-metal contacts
81.05.Bx Metals, semimetals, and alloys
73.23.-b Electronic transport in mesoscopic systems
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)
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Magneto-optical effects from nanophase α-Fe and Fe3O4 precipitates formed in yttrium-stabilized ZrO2 by ion implantation and annealing

S. Honda, F. A. Modine, A. Meldrum, J. D. Budai, T. E. Haynes, and L. A. Boatner

Appl. Phys. Lett. 77, 711 (2000); http://dx.doi.org/10.1063/1.127094 (3 pages) | Cited 18 times

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Magneto-optically active nanocomposite structures have been created by using ion implantation and thermal processing to form precipitated layers of ferromagnetic α-Fe or ferrimagnetic Fe3O4 that are embedded in the near-surface region of (100)-oriented yttrium stabilized ZrO2 (YSZ). When Fe-implanted YSZ is annealed at 1100 °C in Ar+4%H2, the redox conditions are sufficiently reducing so that metallic Fe is the stable phase. At lower temperatures the annealing conditions become less reducing and Fe3O4 becomes the stable phase. Transmission electron microscopy and x-ray diffraction studies established that each α-Fe or Fe3O4 particle is a single crystal that is crystallographically aligned with respect to the YSZ host. Magneto-optical effects due to both the α-Fe and Fe3O4 nanophase precipitates were found and characterized using magnetic circular dichroism. These magneto-optical effects have potential applications in integrated-optical devices. © 2000 American Institute of Physics.
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78.20.Ls Magneto-optical effects
75.50.Kj Amorphous and quasicrystalline magnetic materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Bb Fe and its alloys
75.50.Gg Ferrimagnetics
61.72.up Other materials
61.72.Cc Kinetics of defect formation and annealing
81.40.Rs Electrical and magnetic properties related to treatment conditions
81.40.Tv Optical and dielectric properties related to treatment conditions
81.40.Gh Other heat and thermomechanical treatments
61.46.-w Structure of nanoscale materials
64.75.-g Phase equilibria
81.30.Mh Solid-phase precipitation

Near-room-temperature tunneling magnetoresistance in a trilayer La0.67Sr0.33MnO3/La0.85Sr0.15MnO3/La0.67Sr0.33MnO3 device

H. Q. Yin, J.-S. Zhou, and J. B. Goodenough

Appl. Phys. Lett. 77, 714 (2000); http://dx.doi.org/10.1063/1.127095 (3 pages) | Cited 16 times

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A trilayer La0.67Sr0.33MnO3/La0.85Sr0.15MnO3/La0.67Sr0.33MnO3 tunneling magnetoresistance (TMR) device has been epitaxially produced on a SrTiO3 substrate. The current–voltage curves show that tunneling process dominates the carrier transfer across the junction near room temperature. However, the tunneling effect becomes weak with decreasing temperature. Magnetoresistance of about 4%–6% has been observed below room temperature. The temperature dependence of TMR appears correlated to both the tunneling effect cross the junction and the spin polarization in La0.67Sr0.33MnO3 layers. The temperature dependence of the TMR effect in this device is different from that of other devices based on colossal magnetoresistance materials. © 2000 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.47.Gk Colossal magnetoresistance
75.45.+j Macroscopic quantum phenomena in magnetic systems
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.50.Dd Nonmetallic ferromagnetic materials

Noise imaging in stroboscopic ultrafast microscopy

M. R. Freeman, R. W. Hunt, and G. M. Steeves

Appl. Phys. Lett. 77, 717 (2000); http://dx.doi.org/10.1063/1.127096 (3 pages) | Cited 6 times

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We describe a method for studying the presence of stochastic sample behavior within stroboscopically averaged time-resolved imaging experiments. The technique is based upon continuous noise analysis concurrent with signal acquisition. An example is presented in which details of random magnetic switching are exposed in a time-resolved scanning Kerr microscopy measurement. © 2000 American Institute of Physics.
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07.60.Pb Conventional optical microscopes
06.60.Jn High-speed techniques (microsecond to femtosecond)
78.47.-p Spectroscopy of solid state dynamics
05.40.Ca Noise
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
78.20.Ls Magneto-optical effects

Spin polarization of tunneling current from ferromagnet/Al2O3 interfaces using copper-doped aluminum superconducting films

D. J. Monsma and S. S. P. Parkin

Appl. Phys. Lett. 77, 720 (2000); http://dx.doi.org/10.1063/1.127097 (3 pages) | Cited 112 times

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Superconducting Cu-doped Al films sputtered at room temperature (RT) show improved characteristics for superconductor–insulator–ferromagnet spin-polarization measurements as compared to dirty Al films evaporated at 77 K. Detailed analysis including temperature, depairing and spin-orbit effects reveal spin-polarization values for a large variety of ferromagnetic transition-metal alloys. The high-spin polarization for these RT-sputtered junctions is consistent with large tunnel magnetoresistance values observed in similarly sputtered magnetic tunnel junctions. © 2000 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.45.+j Macroscopic quantum phenomena in magnetic systems
74.78.-w Superconducting films and low-dimensional structures
74.50.+r Tunneling phenomena; Josephson effects
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

Giant magnetoresistance of the La1−xAgxMnO3 polycrystalline inhomogeneous granular system

T. Tang, Q. Q. Cao, K. M. Gu, H. Y. Xu, S. Y. Zhang, and Y. W. Du

Appl. Phys. Lett. 77, 723 (2000); http://dx.doi.org/10.1063/1.127098 (3 pages) | Cited 46 times

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A series of bulk polycrystalline La1−xAgxMnO3 samples with x ranging nominally from 0 to 0.5 were prepared by conventional solid-state reaction processing in air. X-ray diffraction patterns show that the samples contain a single perovskite phase when x ⩽ 0.25, and are composed of two phases (a magnetic perovskite phase and a nonmagnetic Ag-rich phase) for x>0.25. It is found that, in this series of polycrystalline samples, maximum magnetoresistance occurs for x = 0.30, i.e., for a composite of the two phases whose magnetoresistance ratio is about 25.5% at room temperature. The enhancement of the magnetoresistance effect in such an inhomogeneous granular system can be attributed to the spin-dependent scattering of electrons at the interface of the two phases. © 2000 American Institute of Physics.
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75.50.Dd Nonmetallic ferromagnetic materials
75.47.De Giant magnetoresistance
75.47.Gk Colossal magnetoresistance
81.05.Rm Porous materials; granular materials
72.20.My Galvanomagnetic and other magnetotransport effects
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)

Atomic-scale analysis of CoFe/Cu and CoFe/NiFe interfaces

D. J. Larson, P. H. Clifton, N. Tabat, A. Cerezo, A. K. Petford-Long, R. L. Martens, and T. F. Kelly

Appl. Phys. Lett. 77, 726 (2000); http://dx.doi.org/10.1063/1.127099 (3 pages) | Cited 32 times

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Internal interfaces in metallic multilayers grown on planar silicon substrates have been chemically analyzed with atomic resolution using three-dimensional atom probe microscopy. The structure studied was a NiFe/CoFe/Cu/CoFe multilayer grown with (111) texture. Atom probe measurements across the NiFe/CoFe interfaces yield widths of 1.1±0.2 nm for NiFe grown on CoFe and 1.7±0.2 nm for CoFe grown on NiFe. The widths of interfaces between CoFe and Cu layers vary as well, with values of 0.82±0.10 nm for CoFe grown on Cu, but only 0.47±0.15 nm for Cu grown on CoFe. In addition, the Fe concentration is enriched at the interface where Cu is grown on CoFe, and depleted where CoFe is grown on Cu. These results indicate that the Fe segregates to the surface during the deposition of CoFe so that the composition at the top of this layer is Fe rich. © 2000 American Institute of Physics.
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68.35.Dv Composition, segregation; defects and impurities
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.47.De Giant magnetoresistance
68.35.Fx Diffusion; interface formation
64.75.-g Phase equilibria
68.35.Ct Interface structure and roughness
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
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Significant reduction of leakage current in the TiO2/Si structure by the insertion of the CeO2 intermediate layer

Geunhag Bae, Youngil Song, Donggeun Jung, and Yonghan Roh

Appl. Phys. Lett. 77, 729 (2000); http://dx.doi.org/10.1063/1.127100 (3 pages) | Cited 3 times

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The insertion of the CeO2 intermediate layer between the TiO2 layer and the Si substrate reduced the leakage current significantly after rapid thermal annealing (RTA) in O2 ambient for 3 min. After RTA, the TiO2/CeO2/Si structure showed a significantly lower leakage current than the TiO2/Si structure. At a proper voltage of −2 V, which was defined as the difference between the applied gate bias and the flatband voltage, the leakage current density of the TiO2/CeO2/Si structure was ∼ 10−8 A/cm2, while the leakage current density of the TiO2/Si sample was ∼ 10−2 A/cm2. The formation of the intermixed structure of TiO2 and CeO2 at the TiO2/CeO2 interface by RTA was thought to contribute to the reduction of the leakage current. © 2000 American Institute of Physics.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
61.72.Cc Kinetics of defect formation and annealing

Cluster polarization of Cd2Nb2O7 compound

Chen Ang, L. E. Cross, Ruyan Guo, and A. S. Bhalla

Appl. Phys. Lett. 77, 732 (2000); http://dx.doi.org/10.1063/1.127101 (3 pages) | Cited 23 times

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The direct-current (dc) electric-field dependence of dielectric constant around paraelectric–ferroelectric transition in Cd2Nb2O7 has been studied. The results show significant suppression of the dielectric constant by the application of dc bias. The electric-field dependence of the dielectric constant at the temperature around paraelectric–ferroelectric phase transition can be well described by the modified Devenshire relation including a cluster term, i.e., ε(E) = ε1−ε2E2+ε3E4+(Px/ε0)[cosh(Ex)]−2. The fit parameters indicate that the polar-cluster carries polarization P = ∼ 0.5–2.5 mC/m2 with the cluster size of L = ∼ 11–15 nm. © 2000 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.B- Phase transitions and Curie point
77.22.Ch Permittivity (dielectric function)
77.22.Ej Polarization and depolarization

Dynamics of resonance phenomenon and negative capacitances in the dielectric response of materials

Jean-Claude M’Peko

Appl. Phys. Lett. 77, 735 (2000); http://dx.doi.org/10.1063/1.127102 (3 pages) | Cited 6 times

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Thermoelectric characterization performed in this work on BaFe12O19 and BaTiO3 at 1 kHz involved anomalous negative capacitances over higher temperatures. By using alternating-current analysis techniques, we ratify our previous observations on their association with an inductive component leading to a resonance-type phenomenon. The dynamics of this latter, mostly expected to act rather over higher frequencies (>106 Hz), is carefully examined by using a simple but consistent model. Its large stretching to lower frequencies is found to be caused by the inner dynamics of the material dielectric response when becoming governed, over higher temperatures, by the material–electrode interface properties. © 2000 American Institute of Physics.
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77.22.Ch Permittivity (dielectric function)
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.80.-e Ferroelectricity and antiferroelectricity
77.65.Fs Electromechanical resonance; quartz resonators
72.20.Pa Thermoelectric and thermomagnetic effects
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Experimental demonstration of a leadless quantum-dot cellular automata cell

Islamshah Amlani, Alexei O. Orlov, Ravi K. Kummamuru, Gary H. Bernstein, Craig S. Lent, and Gregory L. Snider

Appl. Phys. Lett. 77, 738 (2000); http://dx.doi.org/10.1063/1.127103 (3 pages) | Cited 25 times

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We present the experimental characterization of a leadless (floating) double-dot system and a leadless quantum-dot cellular automata cell, where aluminum metal islands are connected to the environment only by capacitors. Here, single electron charge transfer can be accomplished only by the exchange of an electron between the dots. The charge state of the dots is monitored using metal islands configured as electrometers. We show improvements in the cell performance relative to leaded dots, and discuss possible implications of our leadless design to the quantum-dot cellular automata logic implementation. © 2000 American Institute of Physics.
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85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
85.35.Ds Quantum interference devices
03.67.Lx Quantum computation architectures and implementations
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

GaAs/InGaAs quantum well infrared photodetector with a cutoff wavelength at 35 μm

A. G. U. Perera, S. G. Matsik, H. C. Liu, M. Gao, M. Buchanan, W. J. Schaff, and W. Yeo

Appl. Phys. Lett. 77, 741 (2000); http://dx.doi.org/10.1063/1.127104 (3 pages) | Cited 23 times

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GaAs/InGaAs far-infrared quantum well photodetectors based on a bound-to-continuum intersubband transition with a (zero response) cutoff wavelength of 35 μm are reported. A peak responsivity of 0.45 A/W and detectivity of 6.0×109 cmmath/W at a wavelength of 31 μm and a temperature of 4.2 K have been experimentally achieved. Infrared response was observed at temperatures up to 18 K. A calculated responsivity spectrum using a bound-to-continuum line shape corrected for phonon absorption is fitted to the experimental response. The calculated line shape without absorption gives a cutoff wavelength of 38 μm with a peak responsivity of 0.50 A/W and a detectivity of 6.6×109 cmmath/W at 32 μm. © 2000 American Institute of Physics.
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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
78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Single-electron detector and counter

N. J. Stone and H. Ahmed

Appl. Phys. Lett. 77, 744 (2000); http://dx.doi.org/10.1063/1.127105 (3 pages) | Cited 8 times

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An electron detector, constructed with highly doped silicon nanowires, is described. It is shown that, at a temperature of 4.2 K, the presence or absence of a single excess electron on a storage node can be recognized. The detector can also be used to count the precise number of electrons transferred to the node. © 2000 American Institute of Physics.
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85.35.Gv Single electron devices
85.35.Ds Quantum interference devices

Selective excitation and photoinduced bleaching of defects in InAlGaAs/GaAs high-power diode lasers

J. W. Tomm, A. Bärwolff, T. Elsaesser, and J. Luft

Appl. Phys. Lett. 77, 747 (2000); http://dx.doi.org/10.1063/1.127106 (3 pages) | Cited 5 times

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Mounting-induced defects in semiconductor quantum-well (QW) lasers are investigated by photocurrent spectroscopy. The defects are located in the laser waveguides and give rise to an absorption band below the QW band gap with a maximum absorption cross section of σ = 2×10−15 cm2. We observe a nonlinear fully reversible photobleaching of the defects and a resulting increase of QW photocurrent upon continuous wave irradiation of the devices, demonstrating a direct interaction between quantum-confined carriers and a defect level. © 2000 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
73.61.Ey III-V semiconductors
73.50.Pz Photoconduction and photovoltaic effects
78.66.Fd III-V semiconductors

Dangling-bond defect state creation in microcrystalline silicon thin-film transistors

R. B. Wehrspohn, M. J. Powell, S. C. Deane, I. D. French, and P. Roca i Cabarrocas

Appl. Phys. Lett. 77, 750 (2000); http://dx.doi.org/10.1063/1.127107 (3 pages) | Cited 22 times

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We analyze the threshold voltage shift in microcrystalline Si thin-film transistors (TFTs), in terms of a recently developed thermalization energy concept for dangling-bond defect state creation in amorphous Si TFTs. The rate of the threshold voltage shift in microcrystalline Si TFTs is much lower than in amorphous Si TFTs, but the characteristic energy for the process, which we identify as the mean energy to break a Si–Si bond, is virtually the same. This suggests that the same basic Si–Si bond breaking process is responsible for the threshold voltage shift in both cases. The lower magnitude in microcrystalline Si TFTs is due to a much lower attempt frequency for the process. We interpret the attempt frequency in amorphous and microcrystalline silicon in terms of the localization length of the electron wave function and the effect of stabilizing H atoms being located only at grain boundaries. © 2000 American Institute of Physics.
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85.30.Tv Field effect devices
71.55.Jv Disordered structures; amorphous and glassy solids
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

GaN/W/W-oxide metal base transistor with very large current gain and power gain

K. Mochizuki, K. Uesugi, P. M. Asbeck, J. Gotoh, T. Mishima, K. Hirata, and H. Oda

Appl. Phys. Lett. 77, 753 (2000); http://dx.doi.org/10.1063/1.127108 (3 pages) | Cited 2 times

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We demonstrate a GaN/W/W-oxide metal base transistor (MBT) whose collector is formed by oxidizing the intrinsic W base. The thickness of the nonoxidized intrinsic base of the fabricated collector-up MBT on a sapphire substrate was estimated to be 2–3 nm. Although the MBT showed large leakage, subtraction of the leakage from collector current revealed that the transistor had a very large small-signal direct current (dc) current gain of 87 dB and a dc power gain of 50 dB. This indicates that the GaN-based MBT is a possible candidate for microwave and millimeterwave amplifiers as well as for high-speed integrated circuits used in optical fiber communication system. © 2000 American Institute of Physics.
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85.30.Pq Bipolar transistors
84.40.-x Radiowave and microwave (including millimeter wave) technology
85.30.De Semiconductor-device characterization, design, and modeling

Tailoring the colossal magnetoresistivity: La0.7(Pb0.63Sr0.37)0.3MnO3 thin-film uncooled bolometer

Alvydas Lisauskas, S. I. Khartsev, and Alex Grishin

Appl. Phys. Lett. 77, 756 (2000); http://dx.doi.org/10.1063/1.127109 (3 pages) | Cited 40 times

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Epitaxial Ca, Sr, and Pb doped manganite films of various compositions and thickness have been prepared to tailor metal-to-semiconductor phase transition to room temperature. Continuous series of solid solutions La0.7(Pb1−xSrx)0.3MnO3 grown by the pulsed laser deposition technique were found to possess superior performance regarding the maximum of temperature coefficient of resistivity (TCR) @300 K. In these films phase transition temperature Tc ranges from 266 to 327 K. We have engineered the film of the optimum composition x = 0.37 exhibiting the maximum of TCR = 7.4% K−1 @295 K. Relatively low excess noise (normalized value γ/n of 3×10−21 cm3) has been achieved due to the epitaxial quality of the fabricated film. Using this film, infrared radiation bolometer demonstrator, operating at room temperature, has been built and tested. The bolometer resolves the noise equivalent temperature difference as low as 120 nK/math and shows signal-to-noise ratio SNR = 8×106 math/K, responsivity math = 0.6 V/W, detectivity D = 0.9×107 cmmath/W, and noise equivalent power NEP = 3×10−8 Wmath at 30 Hz frame frequency. For micromachined thermally isolated La0.7(Pb0.63Sr0.37)0.3MnO3 thin-film bolometer one can expect to get responsivity about 4×103 V/W and detectivity higher than 109 cmmath/W @30 Hz. © 2000 American Institute of Physics.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.60.Gz Photodetectors (including infrared and CCD detectors)
75.47.Gk Colossal magnetoresistance
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.47.De Giant magnetoresistance
75.50.Dd Nonmetallic ferromagnetic materials
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
68.55.Nq Composition and phase identification
81.15.Fg Pulsed laser ablation deposition
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