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Abrupt PN Junctions: Analytical solutions under equilibrium and non-equilibrium
, Article Solid-State Electronics ; Volume 122 , 2016 , Pages 37-44 ; 00381101 (ISSN) ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
We present an explicit solution of carrier and field distributions in abrupt PN junctions under equilibrium. An accurate logarithmic numerical method is implemented and results are compared to the analytical solutions. Analysis of results shows reasonable agreement with numerical solution as well as the depletion layer approximation. We discuss extensions to the asymmetric junctions. Approximate relations for differential capacitance C-V and current-voltage I-V characteristics are also found under non-zero external bias
Diffraction analysis of extraction efficiency for photonic crystal based white light emitting diodes
, Article CLEO/Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference, Munich, 14 June 2009 through 19 June 2009 ; 2009 ; 9781424440801 (ISBN) ; Sodagar, M ; Eftekharian, A ; Khorasani, S ; Sharif University of Technology
2009
Investigation of surface radius variation in design of a lens duct delivery system
, Article Optics and Laser Technology ; Volume 36, Issue 1 , 2004 , Pages 1-10 ; 00303992 (ISSN) ; Sharif University of Technology
2004
Abstract
In this article a ray tracing method is used to study the variation of the entrance and exit surface shape in the different lens ducts systems. Designs with a variety of plane and spherical first and second surfaces are studied. The optimum geometrical conditions for each design in terms of the aperture, length, and the radius of curvature are reported. A comparison is made between the results obtained for ducts with the spherical and plane surfaces and the more efficient design is described. The effect of second-order aspheric shape factor on the device performance is also investigated. This study shows that each design has some advantages and disadvantages, and considering specific...
Thermal considerations on the design and operation of lens ducts
, Article Optics and Laser Technology ; Volume 35, Issue 6 , 2003 , Pages 415-423 ; 00303992 (ISSN) ; Sharif University of Technology
2003
Abstract
In this paper, heat effects due to powerful pump beam in the lens duct delivery system is investigated and subsequent thermal effects are described. Temperature raise in the device, thermal loading, and material considerations for the lens ducts fabrication are reported. For an absorbed intensity of 10 W/cm2 in a 4 cm-long lens duct, the temperature difference between the midpoint and its faces, for a lens duct made from borosilicate is 7.05°C, for sapphire 4.01°C, and for synthetic fused silica is the smallest value of 0.54°C. For a typical absorbed intensity of 1.4 W/cm2 in a 4 cm-long lens duct, with a steady-state time constant of 120 s, the fractional thermal loading is 1.98% for BK-7,...
A model reduction based approach for extracting the diffusion and generation terms of pn junction leakage current
, Article Semiconductor Science and Technology ; Volume 18, Issue 4 , 2003 , Pages 234-240 ; 02681242 (ISSN) ; Fathololoumi, S ; Rashidian, B ; Sharif University of Technology
2003
Abstract
Using a model reduction method, a formula for the ideality factor of a pn junction as a function of the diffusion and generation terms of its reverse current is derived. Using this formula a method for separate computation of these two currents for a pn junction is presented. The validity of the method is investigated using computer simulations for an assumed diode with known ideality factor and total leakage current. Experimental results for two commercially available diodes validate the proposed technique
Diffraction analysis of extraction efficiency for photonic crystal based white light emitting diodes
, Article CLEO/Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference ; 14-19 June , 2009 ; 21622701 (ISSN) ; 9781424440801 (ISBN) ; Sodagar, M ; Eftekharian, A ; Khorasani, S ; Sharif University of Technology
Optical Society of America
2009
A heuristic approach to the realization of the wide-band optical diode effect in photonic crystal waveguides
, Article Journal of Optics (United Kingdom) ; Volume 15, Issue 7 , June , 2013 ; 20408978 (ISSN) ; Rezaei, M ; Fard, A. P ; Mehrany, K ; Sharif University of Technology
2013
Abstract
In this paper a highly efficient optical diode is demonstrated in photonic crystal waveguides with broken spatial symmetry. The structure is made of isotropic linear materials and does not need high power optical beams or strong magnetic fields. While the proposed structure shows almost complete light transmission (>99%) in one direction, it blocks light transmission in the opposite direction. This unidirectional transmission is retained within a wide range of frequencies (>4% of central frequency). In order to achieve an optical diode effect, the optical mode of the waveguide is manipulated by designing an ultra-compact mode converter and an efficient mode filter. The dimensions of the...
An analytical-numerical approach for parameter determination of a five-parameter single-diode model of photovoltaic cells and modules
, Article International Journal of Sustainable Energy ; Volume 35, Issue 4 , 2016 , Pages 396-410 ; 14786451 (ISSN) ; Mokhtari, H ; Azizian, M. R ; Söder, L ; Sharif University of Technology
Taylor and Francis Ltd
2016
Abstract
Parameter extraction of the five-parameter single-diode model of solar cells and modules from experimental data is a challenging problem. These parameters are evaluated from a set of nonlinear equations that cannot be solved analytically. On the other hand, a numerical solution of such equations needs a suitable initial guess to converge to a solution. This paper presents a new set of approximate analytical solutions for the parameters of a five-parameter single-diode model of photovoltaic (PV) cells and modules. The proposed solutions provide a good initial point which guarantees numerical analysis convergence. The proposed technique needs only a few data from the PV current-voltage...
Design and Implement a Short Time Ultra High Voltage Pulser
, M.Sc. Thesis Sharif University of Technology ; Kaboli, Shahriyar (Supervisor)
Abstract
In various industries as a solution to energy production for a short period of time in order to have a high instantanuse power pulsed sources are widely used. This resource is a relatively long period of energy stored in the energy storage element and then this energy in a short period of time the exhaust. Among the most important applications of these resources can be used in radar systems, linear accelerators, pulsed lasers, nuclear fusion, medical applications, etc. Among the most important targets are the following sources can be output pulse quality, reliability and longevity of these resources, efficiency and cost them. From the perspective of the quality of the output pulse, rise time...
An analytical-numerical approach for parameter determination of a five-parameter single-diode model of photovoltaic cells and modules
, Article International Journal of Sustainable Energy ; October , 2013 ; 14786451 (ISSN) ; Mokhtari, H ; Azizian, M. R ; Soder, L ; Sharif University of Technology
2013
Abstract
Parameter extraction of the five-parameter single-diode model of solar cells and modules from experimental data is a challenging problem. These parameters are evaluated from a set of nonlinear equations that cannot be solved analytically. On the other hand, a numerical solution of such equations needs a suitable initial guess to converge to a solution. This paper presents a new set of approximate analytical solutions for the parameters of a five-parameter single-diode model of photovoltaic (PV) cells and modules. The proposed solutions provide a good initial point which guarantees numerical analysis convergence. The proposed technique needs only a few data from the PV current-voltage...
Detemining the thickness of barriers and well of Resonance Tunneling Diodes by specified I-V characteristic
, Article Applied Mechanics and Materials ; Volume 110-116 , 2012 , Pages 5464-5470 ; 16609336 (ISSN) ; 9783037852620 (ISBN) ; Ghorbanalipour, S ; Faez, R ; Sharif University of Technology
Abstract
In this paper, a method of determining physical dimension of Double Barrier Quantum Well (DBQW) of Resonance Tunneling Diodes (RTDs) is presented by using I-V characteristic governing on them. In this procedure, first we have used performance metrics related to RTDs I-V characteristic such as Peak to Valley Current Ratio (PVCR), peak current density (JP), valley current density (JV) and Voltage Swing (VS), and by some other arbitrary points, we have fitted a curve to the RTD current-voltage equation by MATLAB software. Then we have obtained the physical parameter of I-V equation and adjusted some of them with modification coefficients. Next, by choosing the material of barriers and the well...
High-power nanosecond pulse generator with high-voltage srd and gdt switch
, Article IEEE Transactions on Plasma Science ; Volume 43, Issue 9 , April , 2015 , Pages 3268-3276 ; 00933813 (ISSN) ; Hashemi, S. M. A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
A high-power short-pulse generator based on the dual action of two coupled diodes, a high-voltage step recovery diode and a high-current diode, is presented. This is made possible using a gas discharge tube. Both analysis and SPICE simulation show about 20-dB peak power increment. This gives a high output power level of 5.7 MW with 1-ns pulsewidth and 450-kHz repetition rate obtained from an input average power of 7.1 kW. An efficiency of about 73% is obtained with more than 30 dB increase in the average power delivered to a 50-Ω load
Influence of cathode roughness on the performance of F8BT based organic-inorganic light emitting diodes
, Article Organic Electronics: physics, materials, applications ; Volume 16 , 2015 , Pages 87-94 ; 15661199 (ISSN) ; Marandi, M ; Irajizad, A ; Taghavinia, N ; Sharif University of Technology
Elsevier
2015
Abstract
Hybrid light emitting diodes (HyLED) with a structure of FTO/ZnO/F8BT/MoO3/Au/Ag is fabricated and the influence of surface roughness of cathode (FTO/ZnO) is investigated. The roughness of FTO could be decreased from 9.2 nm to 2.2 nm using a mild polishing process. The ZnO film, deposited by spray pyrolysis, functions as an electron injection layer. The roughness of the FTO/ZnO surface is found also highly dependent on the ZnO thickness. For thin ZnO films (20 nm), polishing results in better efficacy and power efficiency of LED devices, with nearly a two times improvement. For thick ZnO films (210 nm), the overall FTO/ZnO roughness is almost independent of the FTO roughness, hence both...
Codesign of ka-band integrated limiter and low noise amplifier
, Article IEEE Transactions on Microwave Theory and Techniques ; Volume 64, Issue 9 , 2016 , Pages 2843-2852 ; 00189480 (ISSN) ; Medi, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
In this paper, a thorough design procedure for concurrent design of integrated antiparallel Schottky-diode-based limiter and low noise amplifier (LNA) is presented. The optimum number of limiter branches, the size and number of diodes in each branch, width of the transmission line loaded by diode branches, and design considerations for input transistor of the LNA are discussed in detail. To improve power handling of the limiter with a minimum impact on overall noise figure (NF), a novel limiter structure is proposed where transistors are utilized in a limiter topology. A design procedure is also introduced for the transistor-based limiter-LNA. Developed methodologies are employed to design...
DSRD-based high-power repetitive short-pulse generator containing GDT: theory and experiment
, Article IEEE Transactions on Plasma Science ; Volume 45, Issue 8 , 2017 , Pages 2341-2350 ; 00933813 (ISSN) ; Hashemi, S. M. A ; Olad Dilmaghanian, M ; Sharif University of Technology
Abstract
A high-power short-pulse generator based on the diode step recovery phenomenon and high repetition rate discharges in a two-electrode gas discharge tube is presented. The proposed circuit is simple and low cost and driven by a low-power source. A full analysis of this generator is presented which, considering the nonlinear behavior of the gas tube, predicts the waveform of the output pulse. The proposed method has been shown to work properly by implementation of a kW-range prototype. Experimental measurements of the output pulse characteristics showed a rise time of 3.5 ns, with pulse repetition rate of 2.3 kHz for a 47-Ω load. The input peak power was 2.4 W, which translated to about...
A two-stage DSRD-based high-power nanosecond pulse generator
, Article IEEE Transactions on Plasma Science ; Volume 46, Issue 2 , February , 2018 , Pages 427-433 ; 00933813 (ISSN) ; Hashemi, S. M. A ; Farzaneh, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
Drift step recovery diodes (DSRDs) have a special place in high-power short-pulse generation. In this paper, a cascaded configuration of two DSRD-based high-power short-pulse generators with gas discharge switches was used. The high-power pulses generated in the first stage feed the second stage in order to generate shorter pulses with higher peak powers. A prototype was implemented based on this idea. In the first stage, 1.2-kV pulses were generated from a 50-V power supply. At the output of the second stage, 2.1-kV pulses with a repetition rate of more than 50 Hz were obtained. The output peak voltage was limited by the breakdown voltage of the used DSRD. Repetitive pulses with 4-ns rise...
Output power variations in two mutually coupled microwave oscillators and the effect of non-linear reactance on the locking bandwidth
, Article IEE Proceedings: Microwaves, Antennas and Propagation ; Volume 150, Issue 2 , 2003 , Pages 61-66 ; 13502417 (ISSN) ; Farzaneh, F ; Sharif University of Technology
2003
Abstract
The locking of two mutually coupled microwave oscillators is considered. The common frequency of oscillation is obtained both without and in the presence of a non-linear reactance. The effect of the non-linear reactance on the locking bandwidth is studied. It is shown analytically that, unlike the common injection locked oscillator case, the locking bandwidth can be either increased or decreased by the non-linearity. The variations in amplitude of oscillations is investigated. It is demonstrated that the total power delivered by the active devices decreases in interinjection locked oscillators
Harmonic content and relaxation resonant frequency of a modulated laser diode
, Article Scientia Iranica ; Volume 16, Issue 2 D , 2009 , Pages 145-156 ; 10263098 (ISSN) ; Bavafa, M ; Chamanzar, M. R ; Khorasani, S ; Sharif University of Technology
2009
Abstract
In this paper, an analysis of the harmonic contents of the optical output power for an in-plane single mode laser diode is performed, and the results are described in detail. In the first step, the absolute value of power for each harmonic is obtained in terms of various laser diode parameters, and the variations of external parameters, such as modulation current, bias current and frequency, are discussed. The analysis is done by direct solution of the rate equations of an arbitrary laser diode for carrier and photon densities. It is known that the optical power has a nonlinear dependence on frequency, and the maximum optical power of each harmonic is attained in its resonance frequency. The...
Enhancing the Stability of Cesium-based Perovskite Quantum Dots Using Zeolitic Imidazolate Framework-8 (ZIF-8)for Optical Applications and Medical Imaging
, M.Sc. Thesis Sharif University of Technology ; Simchi, Abdolreza (Supervisor)
Abstract
In this work, encapsulating cesium-based perovskite quantum dots (PQDs) in zeolitic imidazolate framework-8 (ZIF-8) was investigated in order to enhance their environmental, water and thermal stabilities. It was shown that physical mixing of pre-synthesized PQDs and nanocrystalline ZIF-8 (structure-I) does not have any influence on stability enhancement. In second structure, nanocrystals of perovskite were crystalized in ZIF-8 pores. These nanostructures kept 50% of their initial photoluminescence after 24 hours maintenance in water. In third structure, both perovskite nanoparticles and ZIF-8 structures were crystalized simultaneously which resulted in more efficient encapsulation and kept...
A UHF micro-power CMOS rectifier using a novel diode connected CMOS transistor for micro-sensor and RFID applications
, Article International Conference on Electronic Devices, Systems, and Applications ; 2012 , Pages 234-238 ; 21592047 (ISSN) ; 9781467321631 (ISBN) ; Hamidon, M. N ; Khoddam, M ; Najafi, V ; Sharif University of Technology
2012
Abstract
The design strategy and efficiency optimization of UHF micro-power rectifiers using a novel diode connected MOS transistor is presented. The proposed diode connected MOS transistor uses a new bulk connection which leads to reduce the threshold voltage and leakage current in compare to conventional diode connected transistors. Using the proposed diode in typical rectifiers makes a significant improvement in output voltage and current therefore the efficiency is increased comparing to the same rectifier architectures using conventional diodes. Also a design procedure for efficiency optimization is presented and a superposition method is used to optimize the performance of multiple output...