Characteristics Of Emitter Research Articles

Influence of laser parameters on information capacity of communication channel

Contemporary tendencies in developing computing and communication systems are, more than ever, pointing out the necessity of transfer from computer and information systems to the optic and even quantum ones [1---4]. Saturation of microelectronics potencies can be seen in the simple and obvious facts, i.e. slowdown of effectiveness increase rates for the classical Turing computing systems and transfer to multicore parallel computations in electronics, as well as greater attention is paid to the optical communication channels, memory and data transmission systems, which is due to high density of information pack in the optical spectrum of electromagnetic waves [5---7].Taking into account the classical Shannon's understanding of the information quantity and specific characteristics of an optical communication channel, in this work, we are trying to draw a parallel between the classical communication channel and the quantum one, which enables us, in some simple cases, to consider the approximate dependence of maximum information transmission rate on the key characteristics of laser emitter, including the average transmission power, bandwidth, and polarization.

Measurement and Analysis of Temperature Dependence for Current-Voltage Characteristics of Homogeneous Emitter and Selective Emitter Crystalline Silicon Solar Cells

Solar cells exhibit different power outputs in different climates. In this study, the temperature dependence of open-circuit voltage(V-oc), short-circuit current(I-sc), fill factor(FF) and the efficiency of screen-printed single-crystal silicon solar cells were studied. One group was fabricated with homogeneously-doped emitters and another group was fabricated with selectively-doped emitters. While varying the temperature (25, 40, 60 and 80˚C), the current-voltage characteristics of the cells were measured and the leakage currents extracted from the current-voltage curve. As the temperature increased, both the homogeneously-doped and selectively-doped emitters showed a slight increase in I-sc and a rapid degradation of V-oc. The FF and efficiency also decreased as temperature increased in both groups. The temperature coefficient for each factor was calculated. From the current-voltage curve, we found that the main cause of V-oc degradation was an increase in the intrinsic carrier concentration. The temperature coefficients of the two groups were compared, leading to the idea that structural effects could also affect the temperature dependence of current-voltage characteristics.

Statistical dispersion of the field emission parameters of multipoint cathodes based on a polymer-carbon nanotube composite

Statistical properties of the characteristics of a field-electron emitter based on a polystyrene-carbon nanotube composite have been studied. Experimental data have been used to plot the slope versus intercept of I-U curve in the Fowler-Nordheim coordinates and a histogram of the effective heights of emission centers. Numerical estimations show that this statistics obeys the lognormal distribution law. A series of experiments have been performed for determining the influence of the level of emission current on the character of distribution, and a model describing this dependence is proposed.

Detailed Analysis of Shallow and Heavily-Doped Emitters for Al-BSF Bifacial Solar Cells

A selective emitter structure is a promising approach to improve the cell efficiency of industrial type silicon solar cells by minimizing the losses at the front surface and in the emitter. Selective emitters can be produced by numerous processing sequences, resulting in different doping profiles. This paper focuses on the analysis of emitter formation for bifacial solar cell application. In this research, liquid phosphorus oxy-trichloride (POCl3) has been used as a diffusion source for emitter formation. The diffusion temperature was varied from 800 to 900 °C in order to determine an optimum diffusion profile. In this study, the mask-free diffusion process forms diffused emitter on both side of Si wafer. In order to determine the emitter characteristics, the sheet resistance of Si wafer after POCl3 diffusion process was measured using a four-point probe. Based on the sheet resistance value of ~47 ohm/sq, the emitter has been classified as heavily-doped emitter. The performance analysis using surface photovoltage (SPV) and spectral response presents a diffusion length of 2.19 μm. The POCl3-diffusion and screen printed Al-BSF led to bifacial solar cells with a front surface efficiency of 12.8 % and back surface efficiency of 5.08 %.

Characteristics of silicon solar cell emitter with a reduced diffused phosphorus inactive layer

The diffusion of phosphorus using a phosphorous oxychloride (POCl3) source in silicon has been used widely in crystalline silicon solar cells. The thermal diffusion process in the furnace consists of two steps: pre-deposition and drive-in. The phosphorous doping profile via thermal diffusion often exhibits high concentrations in the surface-near emitter, which result in a recombination increase. This layer, called the dead layer, should be inhibited in order to fabricate high efficiency silicon solar cells. In this paper, the amount of the POCl3 flow rate was varied during the pre-deposition process in order to minimize the dead layer, and the characteristics of the phosphosilicate glass (PSG) and emitter were analyzed. From the secondary ion mass spectroscopy (SIMS) and electrochemical capacitance–voltage profiler (ECV) measurements, the emitter formed using a POCl3 flow rate of 1000 sccm contained the least amount of inactive dopant and resulted in reasonable performance in the silicon solar cell. As the POCl3 flow rate increased, the doped silicon wafer included electrically inactive P near the surface, which functions as a defect degrading the electrical performance of the emitter. As a result of this, the removal of the dead layer containing the inactive P was attempted through dipping the doped wafer in a HF solution. After this process, the emitter saturation current density and implied Voc were improved. The completed solar cells and their external quantum efficiencies at a short wavelength also demonstrated improved performance. A quantitative analysis of the emitter can provide a deeper understanding of methods to improve the electrical characteristics of the silicon solar cell.

Evolution of the characteristics of a field-electron emitter based on nitrocellulose-carbon nanotube composite

Characteristics of a field-electron emitter based on a nitrocelulose-multiwalled carbon nanotube composite have been studied. A new method of the recording and online processing of current-voltage (I–U) characteristics of multipoint field-electron emitters has been developed for monitoring the evolution of their properties. Using this method, we have (i) determined the dependences of the field enhancement factor and number of emission centers on the interelectrode distance, (ii) discovered hysteresis of the I–V curve related to variation of the amplitude of applied voltage pulses, and (iii) revealed the influence of the initial emission current level on the temporal evolution of emitter properties.

Analysis of the frequency characteristics of the spin-injection emitter in the terahertz range using a diffraction grating

A method for the measurement and identification of the radiation frequencies of the spin-injection oscillator in the terahertz frequency range using a diffraction grating is developed and experimentally implemented. For the system consisting of a ferromagnetic rod (Fe) and nanosized ferromagnetic film (Fe3O4 with a thickness of up to 100 nm), the thermal and dynamic components of the radiation that is induced by the current flow are separated. The diffraction peaks at a frequency of about 9.6 THz and a band of 37% at a level of 3 dB and at a frequency of 43.5 THz are demonstrated. It is shown that the intensity of each signal is significantly higher than the thermal background level.

Characterization of carbon nanotube field emitters in pulsed operation mode

Carbon nanotubes (CNTs) are promising candidates as electron sources for novel x-ray tubes. Short pulses, high emission currents, and long-term stability are prerequisites for practical applications in medical x-ray imaging. Here, the authors present field emission from CNTs in pulsed operation mode exhibiting very high stability for 200 cumulative hours and a maximum current of 126 mA corresponding to 202 mA/cm2 at an applied field of 9.3 V/μm. They investigated the correlation of classical emitter characteristics such as threshold field and field enhancement factor to the long-term stability and maximum emission current. This correlation was found to be rather poor. Instead, they observed a steady voltage increase for a fixed current during lifetime experiments. This observation allowed to derive a degradation parameter which determines the emitter quality for pulsed applications. Detailed investigations of the degradation in dependency of pressure, duty cycle, and pulse-on time were performed to predict the stability and lifetime of CNT-based field emitters.

Electrohydrodynamic effect resulting from high-frequency barrier discharge in gas

The formation of an electrohydrodynamic flow in atmospheric air by using a high-frequency barrier discharge distributed over the dielectric surface is investigated. The influence of variations in parameters of a fully solid-state pulse generator (with a peak voltage of 0–12 kV, a tunable repetition rate of 10–25 kHz, and a pulse duration of 7 μs) on the current of plasma ion emitter and velocity characteristics of airflow is considered.

Improved approach to Fowler–Nordheim plot analysis

This article introduces an improved approach to Fowler–Nordheim (FN) plot analysis, based on a new type of intercept correction factor. This factor is more cleanly defined than the factor previously used. General enabling theory is given that applies to any type of FN plot of data that can be fitted using a FN-type equation. Practical use is limited to emission situations where slope correction factors can be reliably predicted. By making a series of well-defined assumptions and approximations, it is shown how the general formulas reduce to provide an improved theory of orthodox FN-plot data analysis. This applies to situations where the circuit current is fully controlled by the emitter characteristics, and tunneling can be treated as taking place through a Schottky–Nordheim (SN) barrier. For orthodox emission, good working formulas make numerical evaluation of the slope correction factor and the new intercept correction factor quick and straightforward. A numerical illustration, using simulated emission data, shows how to use this improved approach to derive values for parameters in the full FN-type equation for the SN barrier. Good self-consistency is demonstrated. The general enabling formulas also pave the way for research aimed at developing analogous data-analysis procedures for nonorthodox emission situations.

Threshold, power, and spectral characteristics of a semiconductor emitter with a fiber Bragg grating

The threshold, power, and spectral characteristics of an emitter with a fiber Bragg grating are calculated. The effect of heating of the active region of a laser diode, its thermal resistance, and radiation power extracted from the cavity of the emitter on these characteristics is investigated. It is shown that satisfactory agreement between the theory and experiment is observed when the heating of the active zone of the laser diode by the pump current flowing through it and the radiation power extracted from the cavity of the emitter are taken into account.

Radar Emitter Recognition Based on PSO-BP Network

According to the problem of emitter characteristic parameters are showed by interval and uneasy to identify, an emitter fusion recognition method based on the PSO-BP neural network is proposed. The method train the network by training samples which are reasonable structured according to the distribution in the interval, so as to determine the network structure and confirm the emitter type through the emitter characteristics parameters. At the same time, the BP neural network is optimized by Particle Swarm Optimization (PSO) algorithm. The coding method of the network output, training data size and deviation rate on the influence of the recognition are researched by simulation, and the validity of this method are verified by the results.

Field Evaluation of Microirrigation Water Application Uniformity

This publication presents procedures to separately evaluate the effects of pressure variations in the pipe network (hydraulic uniformity) and variations due to the emitter characteristics (emitter performance variation) on uniformity of water application. Knowing both of these factors will help an irrigation system manager identify the causes of low application uniformities and the corrections that may be required to improve the uniformity of water application.

Development of a Software to Determine the Emitter Characteristics and the Optimum Length of New Designed Drip Irrigation Laterals

An appropriate design of a drip irrigation system in order to increase the uniformity of water distribution with a high efficiency is of importance. The first step for the design is the determination of suitable length of laterals. In order to do this, the emitter characteristics and the friction losses of new designed laterals on which the emitters are placed must be known by laboratory experiments. On the other hand, mathematical models developed can also be used for the determination of friction losses in drip irrigation laterals. In this study, a software in Visual Basic 6.0 programming language was developed and it helps analyzing the data from a new designed emitter in order to find out the main characteristics and friction losses and to obtain the optimum lateral length of the lateral in the shortest time with an acceptable accuracy in. The software included several options for the selection of in-line or on-line emitter type, pressure compensating or non-pressure compensating emitters. The software calculates the optimum lateral length based on the measurement and model equations and utilizes the step by step procedure. Optimum lateral length criterias in the software such as Cu and qvar for non-pressure compensating emitter and lateral end pressure for compensating emitter were used. The comparison of optimum lateral lengths indicated a very good agreement between the experimentally obtained results and the results from the use of mathematical models for different criteria and different slope conditions. The differences in optimum lateral lengths between the experimental and calculated values obtained from the mathematical models ranged between -0.4 and 0.7%.

Electroforming characteristics of SED emitter in Al-AlN granular films

The Al-AlN granular film was proposed as a cathode emitter of surface-conduction electron-emission display (SED) and the effect of Al-AlN granular films’ resistivity on electroforming in experiment and simulation methods was studied. Electroforming could be successfully completed with appropriate Al-AlN granular film resistivity between 1.98 and 15.10 mΩ·cm, and the corresponding turn-on voltage of electroforming increased from 6.2 to 10.5 V with the resistivity increasing. In addition, a temperature profile on Al-AlN emitter was simulated and the temperature decreased from middle to two sides, which were corresponding to surface morphology of Al-AlN emitter after electroforming.

Simulation of the flow characteristics of a drip irrigation emitter with large eddy methods

Realizing the internal flow visualization inside the drip irrigation emitter is the basis of optimizing the labyrinth path structure and promoting its anti-clogging capability. The Computational Fluid Dynamics (CFD) method has become an effective approach to research the water movement in the labyrinth path of the drip irrigation emitter. In this paper, the standard k-ε model and the Large Eddy Simulation method (LES) were applied to analyze the flow characteristic in the drip irrigation emitter. The results showed that the LES model was more effective to simulate the flow characteristics in the flow path of drip irrigation emitters. Based on this model, the energy dissipation mechanism was explained with the velocity and pressure values from local regions to the whole flow path, and the study of the flow path anti-clogging performance was carried out by way of analyzing the velocity distribution characteristics in different cross sections of the same structure unit.

Hafnium oxide passivation of InGaAs/InP heterostructure bipolar transistors by electron beam evaporation

AbstractIn this contribution, we investigate the passivation of InGaAs/InP heterostructures using plasma assisted e‐beam evaporated hafnium oxide (HfO2). The microstructure and optical properties of the HfO2 layers are first examined by X‐ray reflectivity and spectroscopic ellipsometry on Si substrates. The current gain and breakdown voltage of InGaAs/InP heterostructure bipolar transistors (HBTs) have subsequently been used to evaluate the impact and efficiency of the e‐beam evaporated HfO2 passivation layers. The results from these structures have been contrasted with data from similar samples encapsulated with SiO2 using conventional plasma enhanced chemical vapor deposition. The HfO2 passivated InGaAs/InP HBTs show comparable current gains as compared to unpassivated structures. More importantly, in contrast to SiO2‐PECVD devices, the common emitter characteristics of HfO2 passivated HBTs show no degradation in device breakdown voltage. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Spectral characteristics of a laser emitter designed for pumping and detecting a reference quantum transition of a caesium frequency standard

Experimental and calculated spectral characteristics of a diode laser with a Bragg grating soldered on a thermoelectric cooler are presented. A model of the laser is developed, which takes into account the pressure arising after soldering the Bragg grating on the thermoelectric cooler, as well as temperature and dispersion. Theoretical and experimental spectral characteristics of the laser are compared and their satisfactory agreement is shown.

Surface Passivation of InGaAs/InP HBTs Using Atomic Layer Deposited Al2O3

In this contribution, we investigate the Al2O3 surface passivation of InGaAs/InP heterostructures using thermal atomic layer deposition (ALD) with water vapor, and plasma ALD with oxygen plasma. The microstructure and optical properties of the Al2O3 layers are examined by X-ray reflectivity (XRR) and spectroscopic ellipsometry (SE) on InGaAs/InP epilayers and Si substrates. The dc current gain and breakdown voltage of InGaAs/InP heterostructure bipolar transistors (HBTs) have subsequently been used to evaluate the impact and efficiency of the ALD-Al2O3 passivation layers. The thermal-ALD-Al2O3 passivated InGaAs/InP HBTs show relatively higher current gains as compared to structures passivated using the plasma-ALD process, suggesting differences in the dielectric-semiconductor interface properties. The common emitter characteristics of both (thermal and plasma) ALD-Al2O3 passivated HBTs show, however, fairly comparable device breakdown voltages. These results will be contrasted with results from similar samples passivated with SiO2 using conventional plasma enhanced chemical vapor deposition (PECVD).

Understanding the distribution of iron in multicrystalline silicon after emitter formation: Theoretical model and experiments

We studied the behavior of iron in multicrystalline silicon during phosphorus diffusion by spatially resolved measurements and physical modeling. We present improvements to the previously used models for internal gettering in multicrystalline silicon and phosphorus diffusion gettering. 2-dimensional simulations are used for optimization of the phosphorus diffusion processes for intentionally contaminated wafers regarding the iron distribution, without changing the emitter characteristics. Simulations and experimental results show a reduced interstitial iron concentration after an additional low temperature step at the end of the phosphorus diffusion. The concentration of iron precipitates was reduced by a short annealing at 900°C before the phosphorus diffusion, leading to a carrier lifetime three times higher than compared to the standard process.