Change In Bias Current Research Articles

I-V Characteristics of Polycrystalline CAZTSe Heterojunction Solar Cells at Different Ag Content and Annealing Temperatures

Since the polycrystalline (Cu1-xAgx)2ZnSnSe4 (CAZTSe) demonstrated good optical absorption performance in the visible region, the focus of the present study is to grow the polycrystalline (Cu1-xAgx)2ZnSnSe4 thin films deposited by thermal evaporation method on silicon substrates with 800 nm thickness and 0.53 nm/sec deposition rate as a function of Ag content (0.0,0.1,0.2) and annealing temperature at 373 K, 473 K. From I-V measurements of Al/n-CdS/p-CAZTSe/n-Si(111)/Al heterojunction solar cells under dark and illumination conditions, we observed that the forward bias current changes roughly exponentially with bias voltage and the ideality factor and saturation current dependence on both x content and different temperatures (Ta).

Sub-terahertz feedback interferometry and imaging with emitters in 130 nm BiCMOS technology

In this work, we present the effect of self-mixing in compact terahertz emitters implemented in a 130 nm SiGe BiCMOS technology. The devices are based on a differential Colpitts oscillator topology with optimized emission frequency at the fundamental harmonic. The radiation is out-coupled through the substrate side using a hyper-hemispheric silicon lens. The first source is optimized for 200 GHz and radiates up to 0.525 mW of propagating power. The second source emits up to 0.325 mW at 260 GHz. We demonstrate that in these devices, feedback radiation produces the change in bias current, the magnitude of which can reach up to several percent compared to the bias current itself, enabling feedback interferometric measurements. We demonstrate the applicability of feedback interferometry to perform coherent reflection-type raster-scan imaging.

Novel realizations of digitally controlled low power current controlled current conveyor for tuning filter outputs with constant power consumption

This paper presents a dual output resistance tunable current controlled current conveyor (DO-RTCCCII). In the existing current conveyor the change in bias current is required to alter the design parameter Rx which is the intrinsic resistance of input X terminal. This variation changes the internal dc bias conditions such as saturation margins as well as total power consumption of the block. A resistance trimming block is added at X terminal which is controlled by some programmable bits. The usage of programmable bits helps to achieve the desired response without changing bias current, dc operating point and total power consumption. The port relationships of the DO-RTCCCII block are checked and the circuit and design parameters of current follower, voltage follower are analyzed. The operation of filter circuit is also included to illustrate usefulness of the proposal. The circuit has been designed and simulated using 28 nm CMOS bulk technology model parameters on Cadence Virtuoso/AMS environment (eldo simulator) using 0.75 V supply voltage and results have been verified with post layout netlist.

Effect of Incident Light on Transport Properties of Pulsed Laser Deposited Manganite Thin Films

In this communication, we report the results of different light illumination on electrical transport properties of La0.67Ca0.33Mn0.9Ga0.1O3 (LCMGO) thin films grown on Si (100) ( n-type phosphorus-doped) wafer using Pulsed Laser Deposition (PLD) System. The variation in deposition time changes the thickness of the films. X-ray Diffraction (XRD) reveals the polycrystalline structure of LCMGO thin films. The cross-sectional SEM were taken to determine the thickness of the films with changing deposition time. Atomic Forced Micrographs (AFM) show that island type grains diffuse into one another to form a more uniform distribution of grains as the thickness of the film increases. The charge transport properties have been studied using the I-V measurement at LCMGO/Si interfaces. I-V measurement shows the backwards-diode like the behaviour of the LCMGO/Si p-n junction. The reverse bias current changes under the influence of different incident light illumination. The built-in electric field is generated at the interface when the film was illuminated with UV light. The tunnelling process for backward diode like p-n junction is explained using a modified Simmons model.

Current-Biased Transition Edge Detector of $ \hbox{MgB}_{2}$ Nanowires for Neutrons: Imaging by Scanning Laser

The superconducting MgB2 nanowire detector is biased by a current by a battery-class low voltage, and uses the nuclear reactions with a single neutron and the 10B contained in MgB2. The MgB2 detector consists of a 200-nm-thick MgB2 thin film meander structure of 3 μm line width protected by 300-nm-thick SiO layer. We use enriched boron 10B to enhance the sensitivity. The thermal energy of 2.3 MeV released by the reaction 10 B(n, α)7Li gives 1.83 MeV to 4He and 0.47 MeV to 7Li. The energy dissipation in a restricted space causes a local resistive state in the MgB2 wire, which yields a subtle change in bias current. Through a mutual inductance connected in series with current-biased detector, we are able to measure the event as a voltage pulse. The position-dependent response of the MgB2 detector is investigated by scanning a focused laser spot with the aid of an XYZ piezo-driven stage and an optical fiber with a focusing lens. A clear two-dimensional imaging pattern of the sensor signal well corresponds to the detector geometry. According to our results, the inhomogeneity and position-sensitive nature of the detector are supposed to be critical in governing the detection efficiency of the current-biased transition edge detector, which works only in the narrow temperature regime near Tc.

Spin-transfer-torque switching in spin valve structures with perpendicular, canted, and in-plane magnetic anisotropies

We exploit canted anisotropies as possible means to enhance spin-transfer-torque (STT) and reduce switching currents. The STTs in spin-valve structures with perpendicular, canted, and, as a reference, in-plane magnetic anisotropies were studied. For perpendicular magnetic anisotropy and canted spin valves the thicknesses and number of Co and Pt layers were varied to obtain different angles of the magnetic anisotropy with respect to the sample plane. Point contact measurements were used to measure the change in the switching-field of the magnetization with the change in the bias current applied to the point contact. A larger STT effect, as evidenced by a larger change in the switching magnetic field for the unit change in the dc bias current, was observed for the sample with 45∘ tilt in magnetization compared to a sample with 12∘ tilt. Tilted magnetization of the reference layer causes precessional switching, decreasing the switching energy and time. Micromagnetic simulations were performed to explain the experimental observations.

Low swing differential logic for mixed signal applications

Low swing differential logic operated at a constant bias current is a promising approach to reduce the switching noise in sensitive mixed mode circuits. Most differential logic families do not allow a significant change in bias current between cells so that it is difficult to optimize the power consumption for a required speed. A nonlinear load circuit for differential current-steering logic consisting of a current source in parallel with a diode connected FET is therefore proposed. The logic levels can be easily adjusted with an external supply voltage so that the circuit design is significantly simplified. As an example application a counter for the use in pixel readout chips is presented. The layout area using radiation hard design rules is not significantly larger than CMOS. The logic can be operated at very low power.

Theoretical Study on Wavelength Conversion Based on Cross Phase Modulation Using Semiconductor Optical Amplifiers

Performances of wavelength converted signal by cross phase modulation (XPM) using semiconductor optical amplifiers (SOA's) were studied by the use of the multi-section model. Results show that they are related to both the phase arm bias current of the XPM wavelength converter and its operation. When the conversion is under the in-phase operation, the peak extinction ratio (ER) and the chirp frequency of the converted signal increase according to the decrease of the phase arm bias current, but the input signal power dynamic range decreases. When the converter is under the out-of-phase operation, the chirp frequency decreases with the decrease of the phase arm bias current, while the peak ER and the input power dynamic range keep almost the same when the phase arm bias current changes.

Oscillation frequency in CML and ESCL ring oscillators

In this paper a model to accurately evaluate even in a pencil-and-paper manner the oscillation frequency of a ring oscillator made up by a CML or ESCL differential gate is proposed. The model allows us to simply estimate the oscillation frequency changes due both to the bias current change and to process tolerances. The model was validated by Spice simulations on both 6- and 20-GHz technologies for the CML ring oscillator, and on 0.8-/spl mu/m CMOS process for the ESCL ring oscillator. The estimated oscillation frequency agrees with the simulated one. Indeed, average errors lower than 10% were found.

Multimode electrometer for atmospheric ion measurements

A computer-controlled electrometer capable of either high impedance voltage measurements or femtoampere current measurements has been developed. It is intended for use with a Gerdien ion counter in atmospheric temperatures. Temperature variations can cause significant thermal errors arising from offset voltage and bias current changes that compromise the measurements. Use of high impedance switching permits the offset voltage and input bias currents of the electrometer to be measured, and allows regular software compensations to be applied in both modes.

Modulation Schemes in Low-Cost Microwave Field Sensors

The use of modulation schemes in short-range microwave field sensors are discussed and in particular the ideas are applied to low-cost self-detecting doppler sensors based on a two-terminal negative resistance diode oscillator which acts as a load variation detector. FM-CW and pulse modulation techniques are described which can lead to improved performance in these sensors, and experimental results of bias modulation, varactor modulation, and pulsed operation of transferred-electron oscillators are presented. Modulation techniques can be applied in order to eliminate false alarms due to unwanted targets by enabling the doppler sensor to measure or discriminate target range, and the potential merits of different schemes based on frequency modulation with linear and sinusoidal modulation patterns are explored. A novel environmental profiling technique is proposed which exploits the response of frequency-modulated sensors to multiple stationary targets for use in a versatile short-range surveillance system employing digital processing techniques. The mechanism of pulsed operation in self-detecting sensors is described, and the effects of temperature variations in the active device, which result in frequency chirp, are considered. The technique of extracting the doppler signal from the pulsed bias current using a pulse cancellation circuit is demonstrated, and the effects of bias current changes during the pulse (due to temperature variations) on the use of this type of circuit are discussed.

Resonance phenomena on bias current dependence of AlGaAs double heterostructure laser amplifier

We report the first observation of the resonance phenomena on the bias current dependence of the amplified light output for AlGaAs double heterostructure laser. We also show that this resonance phenomenon is mainly caused by the change in the refractive index of the active layer due to the bias current change in terms of the simple theoretical calculations taking into account the effect of the refractive index change in the active layer.

Optical phase modulation in an injection locked AlGaAs semiconductor laser

Optical phase modulation by injecting coherent CW light into a directly frequency modulated semiconductor laser is reported. Phase modulation was obtained at up to 800 MHz modulation frequency without distortion for a 1.6 GHz full locking bandwidth. A static phase shift of π took place with a 0.48 mA bias current change in the injection locked laser. Experimental and theoretical results showed that the product of the normalised phase deviation by the frequency deviation and the cutoff modulation frequency is constant.

Frequency modulation of GaAlAs injection lasers at microwave frequency rates

Frequency modulation of GaAlAs double heterostructure injection lasers at microwave frequencies is reported for the first time. The lasers are operating at a 0.85 μm wavelength and have been modulated at frequencies up to 2.25 GHz with a modulation index of 2.4. The laser FM modulation is displayed by a high resolution spectral measuring setup comprising a monochromator and a Fabry-Perot interferometer. A simple laser model is presented which allows the static frequency shift of the laser resonance frequency to be calculated as a function of the bias current change. The results are compared with measured data.

Nonlinear behavior of the BARITT diode microwave oscillator

Nonlinear behavior of the free-running BARITT diode oscillator has been observed. Discontinuous changes in oscillation frequency and output power occur as the bias current changes. These non-linearities have been investigated in coaxial and waveguide oscillators and are caused by device and circuit interactions.