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  • 1
    Electronic Resource
    Electronic Resource
    Influence of experimental conditions on the electric field effect in the ceramic (BiPb)2Sr2Ca2Cu3Ox (1997)
    Springer
    Physics of the solid state 39 (1997), S. 1759-1761 
    Details
    ISSN: 1063-7834
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An experimental study is reported of the influence of temperature (T), electric field polarity (±E), as well as of changes in the electrode/insulator/superconductor (E/I/S) measuring system on the field effect in the ceramic (BiPb)2Sr2Ca2Cu3Ox. It has been established that at 77 K and for E⩾60 MV/m the critical current I c and conductivity of the sample increase for I〉I c, irrespective of the field polarity. For lower fields and a negative electrode potential the conductivity in an electric field may decrease. The field effect decreases with increasing temperature, to practically vanish near T c where the sample is still in superconducting state. Experiments carried out with more complex systems E/I/M/I/S and E/I/M/S (M stands for a metallic foil) support the conclusion that it is the external electric field that is responsible for the observed effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1130166
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  • 2
    Electronic Resource
    Electronic Resource
    Low frequency negative capacitance behavior of molecular beam epitaxial GaAs n-low temperature-i-p structure with low temperature layer grown at a low temperature (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 1081-1083 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The GaAs sample under study is a n-low temperature-i-p structure grown by molecular beam epitaxy with a low-temperature (LT) layer grown at 300 °C and annealed at 620 °C for 1 h. Admittance measurements on this sample reveal a negative capacitance at low frequency. This work analyzes the origin of the negative capacitance and its corresponding frequency-dependent conductance by combining two current components: charging–discharging current and the inertial conducting current. Analysis results indicate that the activation energies and time constants of both current components closely resemble each other and should correspond to the same trap. Based on the results presented herein, we can conclude that the negative capacitance at low frequency provides evidence of a generation-recombination center with an activation energy of 0.77 eV in the LT layer. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120971
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  • 3
    Electronic Resource
    Electronic Resource
    Transition of carrier distribution from a strained to relaxed state in InGaAs/GaAs quantum well (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 2985-2987 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This work investigates the transition of carrier distribution from the strained to the relaxed state in In0.2Ga0.8As/GaAs quantum well by measuring capacitance voltage and analyzing x-ray diffraction. According to those results, there is carrier confinement in the In0.2Ga0.8As quantum well with well thickness less than the critical thickness. Increasing the well thickness beyond the critical thickness leads to a significant carrier depletion around the quantum well. Double-crystal x-ray rocking curves reveal that when InGaAs well thickness increases beyond the critical thickness, the interference pattern disappears and relaxation begins to occur from near the bottom InGaAs/GaAs interface while the top interface still remains strained. Results obtained from the critical thickness determined from x-ray diffraction correspond to the transition of carrier distribution, illustrating that the capacitance–voltage measurement is a rather effective means of determining the critical thickness. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369614
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  • 4
    Electronic Resource
    Electronic Resource
    Observation of carrier depletion and emission effects on capacitance dispersion in relaxed In0.2Ga0.8As/GaAs quantum wells (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 2461-2463 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Strong changes in capacitance over frequency are found for highly relaxed In0.2Ga0.8As/GaAs quantum well. The high-frequency dispersion is explained by a resistance–capacitance time constant effect due to the existence of a high resistive layer while the low-frequency dispersion is due to carrier emission from traps. The high-resistance layer is created by carrier depletion when InGaAs thickness increases beyond the critical thickness. Excellent agreement is found between the data from capacitance–frequency spectra and deep-level transient spectroscopy, permitting us to conclude that both the carrier depletion and emission effects observed in capacitance–frequency spectra are due to the existence of an acceptor trap at 0.33 eV. This trap is generated when the InGaAs thickness is beyond its critical thickness and is due to defect states associated with misfit dislocations. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125048
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  • 5
    Electronic Resource
    Electronic Resource
    Low 1/f normal-state resistance noise in high-resistivity YBa2Cu3Oy films (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 133-135 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured 1/f resistance noise at room temperature in laser-ablated YBa2Cu3Oy (YBCO) thin films over a wide range of normal-state resistivities. Surprisingly, the high resistivity films exhibit lower normalized noise powers than the low resistivity films. The lowest normalized noise power is 100 times lower than any previously reported values for single crystals of YBCO and is comparable to the lowest noise levels found in other cuprates. Upon oxygen reduction, the noise power in the high resistivity films increases monotonically whereas it decreases in the low resistivity films. We conclude that the high noise level in YBCO is most likely intrinsic to the structure and due to conduction along the Cu-O chains. Therefore, the low noise power in high resistivity films appears to indicate a degraded chain conductivity. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115507
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  • 6
    Electronic Resource
    Electronic Resource
    Role of 0.66 eV dominant trap in annealed low-temperature grown molecular beam epitaxial GaAs (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 1403-1409 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The sample considered herein is an annealed low-temperature (LT) molecular beam epitaxially grown GaAs of n-LT-i-p structure with the LT layer grown at 300 °C. Characteristics involving the dominant trap level located at about 0.66 eV below the conduction band are obtained by analyzing the data of the admittance spectroscopy, capacitance–voltage, current–voltage, and frequency-dependent conductance experiments. This trap pins the fermi level of the LT layer and makes the LT layer semi-insulating. In this structure, the level interacts with both the conduction band and the valence band with a hole emission time constant characterized by an activation energy of 0.77 eV and a cross section of 1.1×10−13 cm2. This level is also an effective generation-recombination center when the temperature exceeds 300 K. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366844
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  • 7
    Electronic Resource
    Electronic Resource
    Electrical characteristics and deep-level admittance spectroscopies of low-temperature grown GaAs p-i-n structures (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 1255-1258 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The properties of low-temperature grown GaAs are studied via the electrical characterization of p-i-n structures with part of the intrinsic layer grown at 300 °C. Comparisons are made between the low-temperature and normally grown samples. The current of the low-temperature sample is about two orders of magnitude higher than that of the normally grown sample in both forward and reverse bias. From temperature-dependent analysis, the leakage current of the low-temperature sample is contributed by the recombination current through defect levels around the midgap, from which a recombination lifetime of 9.4×10−12 s was obtained. By using admittance spectroscopy we observed a dominant electron level at 0.60 eV with a corresponding capture cross section of 1.0×10−13 cm2 that was not observed in the normally grown sample; thus it is believed to be introduced by the As-rich low-temperature layer. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363837
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  • 8
    Electronic Resource
    Electronic Resource
    Electroabsorption field imaging between coplanar metal contacts on semi-insulating semiconductor epilayers (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 72-74 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We use excitonic electroabsorption field imaging to study the electric field distribution between coplanar gold Schottky contacts on semi-insulating photorefractive AlGaAs epilayers. The field imaging shows consistently large localized enhancements of the electric field adjacent to the anode, followed by a region of reduced field. Complex behavior occurs at the cathode, with high-field regions extending far from the contact. These inhomogeneous near-contact field profiles are determined by the superposition of both diffused and drifted charge which affect the performance of many optoelectronic devices that use planar contacts or striplines on semi-insulating substrates. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116761
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  • 9
    Electronic Resource
    Electronic Resource
    Characterizations of deep levels in SnTe-doped GaSb by admittance spectroscopy (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 1891-1893 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A dominant deep level with an activation energy of 0.23–0.26 eV was observed by admittance spectroscopy for SnTe-doped GaSb layers grown directly on GaAs substrates by molecular beam epitaxy (MBE). The activation energy and capture cross section of the deep level are similar to the levels detected in S-doped and Te-doped GaSb grown by MBE, indicating that this deep level originates either from a native defect or a common impurity in n-type GaSb. The Sb4/Ga flux ratio was found to affect the Hall mobility and concentration of the deep level in a similar way, with an optimal beam equivalent pressure ratio around 7 obtained for GaSb grown at 550 °C, which should correspond to the lowest ratio to maintain a Sb-stabilized surface reconstruction. Analysis of this result suggests that the deep level seen by us is a complex defect. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117468
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  • 10
    Electronic Resource
    Electronic Resource
    Transient and persistent tetrodotoxin-sensitive sodium currents in squid olfactory receptor neurons (1999)
    Springer
    Journal of comparative physiology 184 (1999), S. 63-72 
    Details
    ISSN: 1432-1351
    Keywords: Key words Persistent Na+ current ; Na+ channels ; Cephalopod ; Olfaction ; Patch clamp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Squid olfactory receptor neurons are primary bipolar sensory neurons capable of transducing water-born odorant signals into electrical impulses that are transmitted to the brain. In this study, we have identified and characterized the macroscopic properties of voltage-gated Na+ channels in olfactory receptor neurons from the squid Lolliguncula brevis. Using whole-cell voltage-clamp techniques, we found that the voltage-gated Na+ channels were tetrodotoxin sensitive and had current densities ranging from 5 to 169 pA pF−1. Analyses of the voltage dependence and kinetics revealed interesting differences from voltage-gated Na+ channels in olfactory receptor neurons from other species; the voltage of half-inactivation was shifted to the right and the voltage of half-activation was shifted to the left such that a “window-current” occurred, where 10–18% of the Na+ channels activated and did not inactivate at potentials near action potential threshold. Our findings suggest that in squid olfactory neurons, a subset of voltage-gated Na+ channels may play a role in generating a pacemaker-type current for setting the tonic levels of electrical activity required for transmission of hyperpolarizing odor responses to the brain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003590050306
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