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1
Content available remote Trap-assisted tunnelling current in MIM structures
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EN
A new model is presented of current transport in Metal Insulator Metal (MIM) structures by quantum mechanical tunnelling. In addition to direct tunnelling through an insulating layer, tunnelling via defects present in the insulating layer plays an important role. Examples of the influence of the material and thickness of the insulating layer, energy distribution of traps, and metal work functions are also provided.
EN
The properties of barium titanate (BaTiO3, BT), such as high dielectric constant and resistivity, allow it to find numerous applications in the field of microelectronics. In this work silicon metal-insulator-semiconductor field effect transistor (MISFET) structures with BaTiO3 thin films (containing La2O3 admixture) acting as gate insulator were investigated. The films were produced by means of radio frequency plasma sputtering (RF PS) of sintered BaTiO3 + La2O3 (2% wt.) target. In the paper transfer and output I-V, transconductance and output conductance characteristics of the obtained transistors are presented and discussed. Basic parameters of these devices, such as threshold voltage (VTH) are determined and discussed.
EN
A thin - film floating junction solar cell that requires the deposition of alternating p and n layers has been recently introduced. A four-layer solar cell operates like a thyristor in which the triggering gate is substituted by photogenerated charge carries. In this paper an equivalent electrical circuit model of a four-layer structures is presented. Although the J-V characteristics are still thyristor-like, this thyristor-like solar cell gives an output PV power at any sun radiation intensity.
4
Content available remote 1-kWp photovoltaic system at the
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EN
The paper presents the advanced measurement system being developed for the 1 kWp photovoltaic generator installed at the Technical University of Lodz, at the Department of Microelectronics and Computer Science, in the city centre. The main aim of research is verification of feasibility of photovoltaic generator in polluted environment and influence of I-V characteristics mismatch on long-term performance. The photovoltaic system is equipped with comprehensive monitoring system which collects climatic data and I-V characteristics of all PV modules under operation of PV generator. The monitoring system is based on the custom-made microprocessor board, designed with view of reliability of the data collection. The key module of the system is advanced I-V characteristics scanner with a switching matrix.
EN
A general formula providing the transmission coefficient through a given barrier, sandwiched by semiconductor reservoirs under bias is presented in terms of the incoming carrier energy and the logarithmic wave function derivative at the start of the barrier. Furthermore, the formula involves the carrier effective masses in the barrier and reservoir regions. The procedure employed is based on solving an appropriate Riccati equation governing the logarithmic derivative along the barrier width at the end of which it is known in terms of the carrier energy and applied bias. On account of the facility provided for obtaining the transmission coefficient we obtained the I-V characteristic of a quantum dot carved barrier, which exhibits a region of quite a large negative differential resistance together with a high peak to valley ratio. Under the circumstances, the possibility of developing a nanostructure switch utilizing a small variation in the applied bias exists.
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In this work, the authors compared the properties of multicrystalline silicon solar cells which depended on the kind of following antireflective layers: a-Si:C:H, a-Si:N:H and TiOx. Current-voltage characteristics for multicrystalline silicon solar cells were measured by the use of a computer controlled global spectrum sun simulator under an AM 1.5. The measurements of I-V characteristics allow the determination of basic electrical parameters and efficiency using the double exponential relationship from a two-diode solar cells model. Two key parameters: refractive index and thickness of the film affect the final features of the antireflective coating. Optimisation of these parameters and afterwards the experimental verification lead to the minimalisation of the reflection coefficient that decides about the quality of the antireflective layer. A high quality reflective layer can improve the efficiency of the solar cell even by 30%.
EN
The Internet of Vehicles (IoVs) has become a vital research area in order to enhance passenger and road safety, increasing traffic efficiency and enhanced reliable connectivity. In this regard, for monitoring and controlling the communication between IoVs, routing protocols are deployed. Frequent changes that occur in the topology often leads to major challenges in IoVs, such as dynamic topology changes, shortest routing paths and also scalability. One of the best solutions for such challenges is “clustering”. This study focuses on IoVs’ stability and to create an efficient routing protocol in dynamic environment. In this context, we proposed a novel algorithm called Cluster-based enhanced AODV for IoVs (AODV-CD) to achieve stable and efficient clustering for simplifying routing and ensuring quality of service (QoS). Our proposed protocol enhances the overall network throughput and delivery ratio, with less routing load and less delay compared to AODV. Thus, extensive simulations are carried out in SUMO and NS2 for evaluating the efficiency of the AODV-CD that is superior to the classic AODV and other recent modified AODV algorithms.
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A theoretical analysis of the mid-wavelength infrared range detectors based on the HgCdTe materials for high operating temperatures is presented. Numerical calculations were compared with the experimental data for HgCdTe heterostructures grown by the MOCVD on the GaAs substrates. Theoretical modelling was performed by the commercial platform SimuAPSYS (Crosslight). SimuAPSYS fully supports numerical simulations and helps understand the mechanisms occurring in the detector structures. Theoretical estimates were compared with the dark current density experimental data at the selected characteristic temperatures: 230 K and 300 K. The proper agreement between theoretical and experimental data was reached by changing Auger-1 and Auger-7 recombination rates and Shockley-Read-Hall carrier lifetime. The level of the match was confirmed by a theoretical evaluation of the current responsivity and zero-bias dynamic resistance area product (R0A) of the tested detectors.
EN
Numerical analysis of the dark current (Id) in the type-II superlattice (T2SL) barrier (nBn) detector operated at high temperatures was presented. Theoretical calculations were compared with the experimental results for the nBn detector with the absorber and contact layers in an InAs/InAsSb superlattice separated AlAsSb barrier. Detector structure was grown using MBE technique on a GaAs substrate. The k·p model was used to determine the first electron band and the first heavy and light hole bands in T2SL, as well as to calculate the absorption coefficient. The paper presents the effect of the additional hole barrier on electrical and optical parameters of the nBn structure. According to the principle of the nBn detector operation, the electrons barrier is to prevent the current flow from the contact layer to the absorber, while the holes barrier should be low enough to ensure the flow of optically generated carriers. The barrier height in the valence band (VB) was adjusted by changing the electron affinity of a ternary AlAsSb material. Results of numerical calculations similar to the experimental data were obtained, assuming the presence of a high barrier in VB which, at the same time, lowered the detector current responsivity.
10
Content available Electrical characterization of ISFETs
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EN
Methodology of electrical characterization of ISFETs has been described. It is based on a three-stage approach. First, electrical measurements of ISFET-like MOSFETs and extraction of basic parameters of the MOSFET compact model are performed. Next, mapping of the ISFET channel conductances and a number of other characteristic parameters is carried out using a semi-automatic testing setup. Finally, ISFET sensitivity to solution pH is evaluated. The methodology is applied to characterize ISFETs fabricated in the Institute of Electron Technology (IET).
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This paper presents maps of spatial distributions of the short circuit current Isc(x,y) and the open circuit voltage Uoc(x,y) of the investigated low cost solar cells. Visible differences in values of these parameters were explained by differences in the serial and shunt resistances determined for different points of solar cells from measurements of I–V characteristics. The spectral dependence of the photo voltage of solar cell is also shown, discussed and interpreted in the model of amorphous and crystal silicon.
EN
In this work, we have presented a theoretical study of Au/Ni/GaN Schottky diode based on current-voltage (I-V) measurement for temperature range of 120 K to 400 K. The electrical parameters of Au/Ni/GaN, such as barrier height (Φb), ideality factor and series resistance have been calculated employing the conventional current-voltage (I-V), Cheung and Chattopadhyay method. Also, the variation of Gaussian distribution (P (Φb)) as a function of barrier height (Φb) has been studied. Therefore, the modified [formula] relation has been extracted from (I-V) characteristics, where the values of ΦB0 and A+Simul have been found in different temperature ranges. The obtained results have been compared to the existing experimental data and a good agreement was found.
14
Content available remote The effect of aluminium additive on the electrical properties of ZnO varistors
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EN
Reliable and undisturbed operation of electric and electronic circuits is mainly achieved through the use of appropriate overload protection elements such as overvoltage surge arrestors. The stability of metal oxide varistors which are used insures that the circuits are adequately protected. The point of adding the varistor material with aluminium is the extension of the nonlinearity of I-V characteristic in high current region. In this work, both the aluminium doping for ZnO varistors, and the effect of this doping on the ageing processes in varistors were investigated. The current trend towards the production of better and more robust surge arrestors which utilize mainly ZnO varistors motivated these studies. The fundamental technological impediments include the repeatability of manufactured varistors and their susceptibility to ageing factors such as current shocks, elevated operation temperature and the extended effect of the operation potential. Improving the varistor imperviousness to ageing continues to be an imperative but, as yet, unsolved problem.
EN
Reliable and undisturbed operation of electric and electronic circuits is mainly achieved through the use of appropriate overload protection elements such as overvoltage surge arrestors. The stability of the metal oxide varistors which are used insures that the circuits are adequately protected. The point of adding the varistor material with aluminium is the extension of the I_V characteristic's nonlinearity in high-current region [1]. In this work, both the viability of aluminum doping for ZnO varistors, and the effect of this doping on the ageing processes in varistors were investigated. The current trend is towards the production of better and more robust surge arrestors which utilize mainly ZnO varistors, and it was this trend which motivated these studies. The fundamental technological impediments include the repeatability of manufactured varistors and their susceptibility to ageing factors, such as current shocks, elevated operation temperature and the extended effect of the operation potential. Improving the varistors' imperviousness to ageing continues to be an imperative but, as yet, unsolved problem.
EN
Drift-diffusion computer simulation model available in Synopsys’ Sentaurus TCAD User Guide is used to study electrical and optical characteristics of a separate-confinement heterostructure laser based on AlGaAs. We investigate the role of the width and depth of quantum-well active region, below and above the lasing threshold. The device properties depend on both, the number of bound quantum-well states and on closeness of the highest bound states to conduction or valence band offset. The lasing action may not exist at certain widths or depths of quantum-well, and the threshold current is a discontinuous function of these parameters, at such values of quantum-well width or depth when the highest quantum-well bound states cross conduction or valence band energy offset. The effects are more pronounced at low temperatures. Discontinuities in characteristics are found, at certain conditions, in temperature dependences as well. The carriers scattering time on quantum-well is shown to have a crucial role for the amplitude of discontinuities of these characteristics. The current below the lasing threshold and the threshold current density itself decrease with an increase of quantum-well scattering times and the amplitude of discontinuities decreases then as well.
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