Determination of background doping type in type-II superlattice using capacitance-voltage measurements with double mesa structure.
Abstract not provided.
Fink, D. R.↗
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Approach to fitting parameters and clustering for characterising measured voltage dips based on two-dimensional polarisation ellipses
An alternative approach to characterise real voltage dips is proposed and evaluated in this study. The proposed methodology is based on voltage-space vector solutions, identifying parameters for ellipses trajectories by using the least-squares algorithm applied on a sliding window along the disturbance. The most likely patterns are then estimated through a clustering process based on the k-means algorithm. The objective is to offer an efficient and easily implemented alternative to characterise faults and visualise the most likely instantaneous phase-voltage evolution during events through their corresponding voltage-space vector trajectories. This novel solution minimises the data to be stored but maintains extensive information about the dips including starting and ending transients. The proposed methodology has been applied satisfactorily to real voltage dips obtained from intensive field-measurement campaigns carried out in a Spanish wind power plant up to a time period of several years. A comparison to traditional minimum root mean square-voltage and time-duration classifications is also included in this study.
24 POWER TRANSMISSION AND DISTRIBUTION↗
Coincidence of the Measured Voltage Peak and the Measured Current Inflection Point in Exploding Metals
Exploding Bridgewire (EBW) Detonators and Exploding Foil Initiators (EFI's, e.g. Slappers) have unique current and voltage characteristics marked by a large voltage spike and an inflection point in the current. Mathematically, it is shown that the voltage peak and the current inflection point must align in time. Models concur with the math and show voltage peaks occurring at the same point in time as the inflection point. Circuit analysis is performed to demonstrate why the voltage peak and current inflection point will almost never align in time for an experiment. To correctly analyze exploding metal behavior, the current inflection point and voltage peak must be manually aligned in time. These conclusions apply to single detonators where current and voltage is measured on those detonators. In multi-detonator systems, the conclusions herein apply only for cases where current and voltage are obtained for each detonator individually. The conclusions will begin to break down as measurements become combined.
36 MATERIALS SCIENCE↗
Temperature and voltage measurement in quantum systems far from equilibrium
In this work, we show that a local measurement of temperature and voltage for a quantum system in steady state, arbitrarily far from equilibrium, with arbitrary interactions within the system, is unique when it exists. This is interpreted as a consequence of the second law of thermodynamics. We further derive a necessary and sufficient condition for the existence of a solution. In this regard, we find that a positive temperature solution exists whenever there is no net population inversion. However, when there is a net population inversion, we may characterize the system with a unique negative temperature. Voltage and temperature measurements are treated on an equal footing: They are simultaneously measured in a noninvasive manner, via a weakly coupled thermoelectric probe, defined by requiring vanishing charge and heat dissipation into the probe. Our results strongly suggest that a local temperature measurement without a simultaneous local voltage measurement, or vice versa, is a misleading characterization of the state of a nonequilibrium quantum electron system. These results provide a firm mathematical foundation for voltage and temperature measurements far from equilibrium.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Beam Based RF Voltage Measurements and Longitudinal Beam Tomography at the Fermilab Booster
Increasing proton beam power on neutrino production targets is one of the major goals of the Fermilab long term accelerator programs. In this effort, the Fermilab 8 GeV Booster synchrotron plays a critical role for at least the next two decades. Therefore, understanding the Booster in great detail is important as we continue to improve its performance. For example, it is important to know accurately the available RF power in the Booster by carrying out beam-based measurements in order to specify the needed upgrades to the Booster RF system. Since the Booster magnetic field is changing continuously measuring/calibrating the RF voltage is not a trivial task. Here, we present a beam based method for the RF voltage measurements. Data analysis is carried out using computer programs developed in Python and MATLAB. The method presented here is applicable to any RCS which do not have flat-bottom and flat-top in the acceleration magnetic ramps. We have also carried out longitudinal beam tomography at injection and extraction energies with the data used for RF voltage measurements. Beam based RF voltage measurements and beam tomography were never done before for the Fermilab Booster. The results from these investigations will be very useful in future intensity upgrades.
43 PARTICLE ACCELERATORS↗
Megavolt range voltage measurement in vacuum through a short-circuited line
Method of voltage measurement at a vacuum load by means of homogeneous short-circuited vacuum-isolated line was considered. Prior to appearance of a measured high-voltage pulse, a magnetic field is formed in the line due to the bias current. Biasing provides fulfillment of magnetic electron isolation conditions and strong pressing of an electron layer down to the cathode already at the voltage wave front. As a result, a weak change of the ''hot'' line wave impedance is achieved during a pulse. Theoretical consideration and numerical simulation of the measuring line operation in the presence of bias current basing the applicability of the method was carried out. The method was used to determine the plasma-filled diode voltage at a megavolt voltage level. The absence of electron leakages at the voltage wave propagation of the amplitude {approx_equal}1 MV along the measuring line of the length 2.3 m with the wave impedance of 136 {Omega} and initial bias current of {approx_equal}6 kA was realized.
42 ENGINEERING↗
Comparing the magnetic resonant coupling radiofrequency stimulation to the traditional approaches: Ex-vivo tissue voltage measurement and electromagnetic simulation analysis
Recently, the design concept of magnetic resonant coupling has been adapted to electromagnetic therapy applications such as non-invasive radiofrequency (RF) stimulation. This technique can significantly increase the electric field radiated from the magnetic coil at the stimulation target, and hence enhancing the current flowing through the nerve, thus enabling stimulation. In this paper, the developed magnetic resonant coupling (MRC) stimulation, magnetic stimulation (MS) and transcutaneous electrical nerve stimulation (TENS) are compared. The differences between the MRC RF stimulation and other techniques are presented in terms of the operating mechanism, ex-vivo tissue voltage measurement and electromagnetic simulation analysis. The ev-vivo tissue voltage measurement experiment is performed on the compared devices based on measuring the voltage induced by electromagnetic induction at the tissue. The focusing effect, E field and voltage induced across the tissue, and the attenuation due to the increase of separation between the coil and the target are analyzed. The electromagnetic stimulation will also be performed to obtain the electric field and magnetic field distribution around the biological medium. The electric field intensity is proportional to the induced current and the magnetic field is corresponding to the electromagnetic induction across the biological medium. The comparison between the MRC RF stimulator and the MS and TENS devices revealed that the MRC RF stimulator has several advantages over the others for the applications of inducing current in the biological medium for stimulation purposes.
60 APPLIED LIFE SCIENCES↗
Capacitance voltage measurements on N-type InAs MOS diodes
Capacitance voltage measurements on interface of pyrolytically deposited n-type silicon dioxide- InAs MOS diodes as function of admittance at room and 77 K temperatures
Dockerty, R. C.↗
Voltage measurements at the vacuum post-hole convolute of the Z pulsed-power accelerator
Presented are voltage measurements taken near the load region on the Z pulsed-power accelerator using an inductive voltage monitor (IVM). Specifically, the IVM was connected to, and thus monitored the voltage at, the bottom level of the accelerator’s vacuum double post-hole convolute. Additional voltage and current measurements were taken at the accelerator’s vacuum-insulator stack (at a radius of 1.6 m) by using standard D-dot and B-dot probes, respectively. During postprocessing, the measurements taken at the stack were translated to the location of the IVM measurements by using a lossless propagation model of the Z accelerator’s magnetically insulated transmission lines (MITLs) and a lumped inductor model of the vacuum post-hole convolute. Across a wide variety of experiments conducted on the Z accelerator, the voltage histories obtained from the IVM and the lossless propagation technique agree well in overall shape and magnitude. However, large-amplitude, high-frequency oscillations are more pronounced in the IVM records. It is unclear whether these larger oscillations represent true voltage oscillations at the convolute or if they are due to noise pickup and/or transit-time effects and other resonant modes in the IVM. Results using a transit-time-correction technique and Fourier analysis support the latter. Regardless of which interpretation is correct, both true voltage oscillations and the excitement of resonant modes could be the result of transient electrical breakdowns in the post-hole convolute, though more information is required to determine definitively if such breakdowns occurred. Despite the larger oscillations in the IVM records, the general agreement found between the lossless propagation results and the results of the IVM shows that large voltages are transmitted efficiently through the MITLs on Z. These results are complementary to previous studies [R. D. McBride et al ., Phys. Rev. ST Accel . Beams 13, 120401 (2010)] that showed efficient transmission of large currents through the MITLs on Z. Altogether, the two studies demonstrate the overall efficient delivery of very large electrical powers through the MITLs on Z.
42 ENGINEERING↗
Characterization of AlN/AlGaN/GaN:C heterostructures grown on Si(111) using atom probe tomography, secondary ion mass spectrometry, and vertical current-voltage measurements
Complementary studies of atom probe tomography, secondary ion mass spectrometry, and vertical current-voltage measurements are carried out in order to unravel the influence of C-doping of GaN on the vertical leakage current of AlN/AlGaN/GaN:C heterostructures. A systematic increment of the vertical blocking voltage at a given current density is observed in the structures, when moving from the nominally undoped conditions—corresponding to a residual C-background of ∼10{sup 17 }cm{sup −3}—to a C-content of ∼10{sup 19 }cm{sup −3} in the GaN layer. The value of the vertical blocking voltage saturates for C concentrations higher than ∼10{sup 19 }cm{sup −3}. Atom probe tomography confirms the homogeneity of the GaN:C layers, demonstrating that there is no clustering at C-concentrations as high as 10{sup 20 }cm{sup −3}. It is inferred that the vertical blocking voltage saturation is not likely to be related to C-clustering.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Quantum States Probed By Temperature Dependence Capacitance-Voltage Measurements For InP/GaAs Type-II Ultrathin Quantum Well
We report on the temperature dependent capacitance-voltage measurements on InP/GaAs ultrathin quantum well (QW). We observe a peak in apparent carrier distribution (ACD) profile at around the geometrical position of the QW. Peak value of the ACD profile increases, while it's width decreases with reducing temperature indicating that the peak in ACD is due to the accumulation of two dimensional electrons occupying the quantum states in ultrathin QW.
36 MATERIALS SCIENCE↗
Sampling Rate Comparison for Distribution System Voltage Measurements
Measurement of the voltage delivered by an electric distribution is a relatively straight forward task. When determining the harmonic distortion in the voltage, matters associated with what orders of the 50/60 Hz harmonics to be analyzed dictate the sampling rate. A study addressing this matter is presented.
42 ENGINEERING↗
Electrochemical capacitance voltage measurements in highly doped silicon and silicon-germanium alloys
The electrochemical capacitance voltage technique has been used on highly boron doped SiGe and Si layers. Although the boron concentration is constant over the space charge depth, the 1/C{sup 2} versus voltage curves are not linear. They indeed present a negative curvature. This can be explained by the existence of deep acceptors which ionise under a high electric field (large inverse voltage) and not at a low inverse voltage. The measured doping concentration in the electrochemical capacitance voltage increases strongly as the inverse voltage increases. Thanks to a comparison with the boron concentration measured by secondary ions mass spectrometry, we show that the relevant doping concentrations in device layers are obtained for small inverse voltage in agreement with the existence of deep acceptors. At the large inverse voltage, the measured doping can be more than twice larger than the boron concentration measured with a secondary ion mass spectroscopy.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
High altitude current-voltage measurement of GaAs/Ge solar cells
Measurements of high-voltage (Voc of 1.2 V) gallium arsenide on germanium tandem junction solar cells at air mass 0.22 showed that the insolation in the red portion of the solar spectrum is insufficient to obtain high fill factor. On the basis of measurements in the LeRC X-25L solar simulator, these cells were believed to be as efficient as 21.68 percent AM0. Solar simulator spectrum errors in the red end allowed the fill factor to be as high as 78.7 percent. When a similar cell's current-voltage characteristic was measured at high altitude in the NASA Lear Jet Facility, a loss of 15 percentage points in fill factor was observed. This decrease was caused by insufficient current in the germanium bottom cell of the tandem stack.
Hart, Russell E., Jr.↗
Determination of polarization fields in group III-nitride heterostructures by capacitance-voltage-measurements
The polarization fields in wurtzite group III-nitrides strongly influence the optical properties of InAlGaN-based light emitters, e.g., the electron and hole wave function overlap in quantum wells. In this paper, we propose a new approach to determine these fields by capacitance-voltage measurements (CVM). Sheet charges generated by a change of the microscopic polarization at heterointerfaces influence the charge distribution in PIN junctions and therefore the depletion width and the capacitance. We show that it is possible to determine the strength and direction of the internal fields by comparing the depletion widths of two PIN junctions, one influenced by internal polarization fields and one without as a reference. For comparison, we conducted coupled Poisson/carrier transport simulations on the CVM of the polarization-influenced sample. We also demonstrate the feasibility and limits of the method by determining the fields in GaN/InGaN and GaN/AlGaN double heterostructures on (0001) c-plane grown by metal organic vapor phase epitaxy and compare both evaluation methods. The method yields (−0.50 ± 0.07) MV/cm for In{sub 0.08}Ga{sub 0.92}N/GaN, (0.90 ± 0.13) MV/cm for Al{sub 0.18}Ga{sub 0.82}N/GaN, and (2.0 ± 0.3) MV/cm for Al{sub 0.31}Ga{sub 0.69}N/GaN heterostructures.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Approximation of the maximum frequency of operation for point‐contact MIM diodes from DC current against voltage measurements
Point‐contact metal–insulator–metal (MIM) diodes have been used for detection and mixing at frequencies as high as 520 THz. In detection, the current responsivity (CR), defined as the change in the DC current caused by an incremental change in the high‐frequency input power, depends on the dimensions of the diode and the test fixture. However, other researchers have shown that the intrinsic current responsivity (ICR) which sets an upper bound for the CR may be determined from DC current against voltage measurements. Additional calculations from DC measurements have been used to determine an upper bound for the maximum frequency of operation.
Snyder, G.↗
Deep-level transient spectroscopy of Al(x)Ga(1-x)As/GaAs using nondestructive acousto-electric voltage measurement
The amplitude and the transient time constant of the acoustoelectric voltage were measured as a function of temperature to determine the activation energy of deep levels in Al(x)Ga(1-x)As/GaAs grown by molecular-beam epitaxy. In comparison to other methods based on monitoring the capacitance transient, deep-level transient spectroscopy has several advantages. The technique is nondestructive and highly sensitive, and, because of the dependence of the polarity of the acoustoelectric voltage on the carrier type, it yields information about the charge of the transient carriers and the type of deep traps involved in the release or trapping of these carriers.
Tabib-Azar, Massood↗