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ABSTRACT: A self-isolating, lateral IGBT device with high voltage blocking capability (>700 V), high on-state current density (150 A/cm<sup>2</sup> at Vds=4 V) and very fast turn-off (< 50 ns), realized in membrane on bulk Si technology is reported here. The device has been manufactured using a standard 5 V, 0.35 mum bulk CMOS process on 8" wafers with the addition of two masks: i) n-drift for the HV blocking region and ii) back-side Deep RIE (DRIE) for membrane formation. In comparison to PowerBrane on SOI, earlier reported by us, PowerBrane on bulk Si LIGBTs offer higher maximum power density due to better thermal dissipation and more robust operation including unclamped inductive switching and short circuit capability. Reliability of bulk-Si PowerBrane chips in plastic packages has been evaluated through HTRB tests and no failures have been observed after more than 1000 hours of stress. The DRIE step used for selective removal of portions of the silicon substrate, the key feature of PowerBrane technology, offers an effective solution for isolation of the high-voltage power LIGBT(s) from the control circuitry in monolithically integrated Power ICs. In addition, use of bulk Si wafers instead of more expensive SOI substrates reduces the manufacturing costs of PowerBrane-based Power ICs without compromising performance.
Power Semiconductor Devices & IC's, 2009. ISPSD 2009. 21st International Symposium on; 07/2009
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ABSTRACT: Nanogripper structures using aligned multiwall carbon nanotubes (MWCNTs) are demonstrated and their electromechanical properties have been studied in this paper. The balance of electrostatic force, together with elastostatic force and van der Waals force determines the driving conditions. A triode structure drastically reduces the bias between two moving parts, which consist of MWCNTs. Low bias also enables low power consumption as well as the reduction of electrical damage to an object. The moving parts can keep the same state without any applied biases after bending and connection. This also enables power saving during driving. The device can be a base structure for various nanorobotic or other nanoelectromechanical devices.
IEEE Transactions on Nanotechnology 08/2008; · 2.29 Impact Factor
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ABSTRACT: A step change in performance and reliability of thick SOI membrane devices compared to earlier generation of devices on ultra-thin SOI membranes is reported in here. The membrane concept first reported offered a landmark improvement in the trade-off between switching losses and breakdown capability (in excess of 700V) but its current capability was limited by the thickness of the silicon membrane (around 30 A/cm<sup>2</sup> for LIGBTs on 0.25 mum silicon membranes, achieving a loss related power density approaching 100 W/cm<sup>2</sup> ). This paper reports on membrane power devices with current densities which approach the best of those offered by vertical devices (current density greater than 100 A/cm with power density of 180 W/cm<sup>2</sup> ), without sacrificing switching speed (t<sub>off</sub> < 60 ns for 1.5 mum membranes). HTRB results showing 1000 h+ operation at 125degC at 80% of the rated voltage are also presented. Finally, it is shown that both the static and dynamic high temperature operation of thick membrane LIGBTs is superior to that of state-of-the-art integrated LDMOSFETs.
Power Semiconductor Devices and IC's, 2008. ISPSD '08. 20th International Symposium on; 06/2008
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ABSTRACT: High conductivity 2 kV single crystal diamond Schottky metal-intrinsic-p<sup>+</sup> (m-i-p<sup>+</sup>) diodes utilising horizontally and vertically oriented thin highly boron-doped delta layers are presented in this work. Numerical analysis adopting diamond specific models previously reported indicate that these structural modifications drastically improve the forward performance of diamond Schottky diodes, realising current densities up to 50 A/cm<sup>2</sup> for a forward bias of 3 V, without compromising the reverse performance of the device. This is a 20 fold performance improvement from the uniformly intrinsic diamond Schottky diode.
Power Semiconductor Devices and IC's, 2008. ISPSD '08. 20th International Symposium on; 06/2008
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Applied Physics Letters 01/2008; 93(11). · 3.84 Impact Factor
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M. Brezeanu,
T. Butler,
N. Rupesinghe,
S.J. Rashid,
M. Avram, G.A.J. Amaratunga,
F. Udrea,
M. Dixon,
D. Twitchen,
A. Garraway,
D. Chamund,
P. Taylor
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ABSTRACT: Its outstanding electronic properties and the recent advances in growing single-crystal chemically vapour-deposited substrates have made diamond a candidate for high-power applications. Diamond Schottky diodes have the potential of being an alternative to silicon p-i-n and SiC Schottky diodes in power electronic circuits. Extensive experimental and theoretical results, for both on- and off-state behaviour of metal-insulator-p-type diamond Schottky structures, are presented here. The temperature dependence of the forward characteristics and electrical performance of a termination structure suitable for unipolar diamond devices are also presented.
IET Circuits Devices & Systems 11/2007; · 0.55 Impact Factor
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ABSTRACT: Photovoltaic (PV) power has been successfully used for over five decades. Whether in dc or ac form, photovoltaic cells provide power for systems in many applications on earth and space. Its principles of operation are therefore well understood, and circuit equivalents have been developed that accurately model the nonlinear relationship between the current and voltage of a photovoltaic cell. With the improved efficiencies of power electronics converters, it is now possible to operate photovoltaic system about its maximum power point (MPP) in order to improve the overall system efficiency. Hitherto, this problem has been tackled using tracking (MPPT) algorithms that iteratively find the point of maximum power and respond to changes in solar irradiance accordingly. A mathematical manipulation that uses the mean value theorem is presented here that provides the analytic solution of a point in a close neighborhood of the MPP. It is thoroughly proved that this point is enclosed in a ball of small radius that also contains the MPP and therefore can practically be considered as the MPP. Since the solution is analytic, no iterative schemes are necessary, and only a periodic measurement is required to adjust to changes in solar irradiance. A circuit is implemented that shows the validity of the theory and the accuracy of the solution.
Circuits and Systems I: Regular Papers, IEEE Transactions on 10/2007; · 1.97 Impact Factor
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E. Minoux,
L. Hudanski,
K.B.K. Teo,
O. Groening,
F. Peauger,
D. Dieumegard,
J.-P. Schnell,
L. Gangloff, G.A.J. Amaratunga,
W.I. Milne,
J. Robertson,
P. Legagneux
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ABSTRACT: Cold cathodes based on carbon nanotubes allow to produce a modulated electron beam. Using an array of vertically aligned CNs that exhibit an aspect ratio of about 200, we demonstrated the modulation of a high current density beam (~ 1 A/cm<sup>2</sup> at 1.5 and 32 GHz frequencies. Such CN cathodes are very promising for their use in a new generation of compact, highly efficient and low cost amplifiers that operate between 10 and 100 GHz.
Nanotechnology, 2007. IEEE-NANO 2007. 7th IEEE Conference on; 09/2007
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ABSTRACT: In this paper we report a lateral insulated gate bipolar device with an embedded anti-parallel diode (body diode) for use in half bridge or full bridge configurations. The device offers ultra-fast switching speed and low on-state resistance and is based on an SOI proprietary process earlier reported by us (F. Udrea, et. al., 2004). The device features double CMOS gates operated from an integrated CMOS controller. When the anode gate is biased negatively with respect to the anode a hole inversion layer is formed at the surface of the n-well which leads to enhanced injection of holes and therefore a lower on-state resistance. When the device is turned-off by inactivating both the cathode and anode gates the 'extra' inversion layer emitter is physically suppressed and the device turns-off fast. The device is experimentally demonstrated with full set of measured characteristics and compared on the same wafer with a classical LIGBT, an anode-shorted LIGBT and an LDMOSFET. It is shown that the Double Gate Enhanced Injection device offers a remarkably better switching/on-state/breakdown trade-off and, very importantly in some applications, it benefits from a fast, low on-state, embedded anti-parallel diode.
Power Semiconductor Devices and IC's, 2007. ISPSD '07. 19th International Symposium on; 06/2007
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ABSTRACT: This paper presents a compact integrated power electronic module (IPEM) which seeks to overcome the volumetric power density limitations of conventional packaging technologies. A key innovation has been the development of a substrate sandwich structure which permits double side cooling of the embedded dies whilst controlling the mechanical stresses both within the module and at the heat exchanger interface. A 3-phase inverter module has been developed, integrating the sandwich structures with high efficiency impingement coolers, delink capacitance and gate drive units. Full details of the IPEM construction and electrical evaluation are given in the paper.
Power Semiconductor Devices and IC's, 2007. ISPSD '07. 19th International Symposium on; 06/2007
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ABSTRACT: The `PLUMBICON' was one of the first successful imaging tubes using amorphous selenium (a-Se) and many followed. Significant properties of a-Se based imaging tubes have been rediscovered through the invention of the `HARP (high-gain avalanche rushing amorphous photoconductor)', but its operational mechanism and the physics, however are yet poorly described. Previously, we have fabricated photodetectors using nitrogen (N)-doped diamond as a cold cathode and a-Se as a photoconducting target, which successfully responded to light illumination, The device performance,in this case, deteriorates after continuous use largely due to the degradation of a-Se. In this paper, a-Se and amorphous arsenic selenide (a-As2Se3) films have been deposited Stoichiometry has been determined by XPS (X-ray photoelectron spectroscopy) followed by Raman spectroscopy characterization. We have found that even an extremely weak incident laser power causes sample degradation during signal accumulation. We speculate that either the incident laser itself and/or the temperature rise due to illumination causes the phase transition in a-Se films. In addition, when As is added into the film, the phase transition leading the degradation is hardly observed, implying that As affects the formation of crystalline Se making chemical bonds in the crystallographic network stronger. (c) 2006 Elsevier B.V. All rights reserved.
Journal of Non-Crystalline Solids 01/2007; 353(3):308-312. · 1.54 Impact Factor
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ABSTRACT: Diamond Schottky power diodes are currently subject to extensive research. In this paper, the on-state capability of this type of structures is assessed. Measured forward characteristics for different temperatures are included and the use of gold, nickel and aluminium as Schottky metal is evaluated. A theoretical study regarding the influence of different doping profiles at the drift-substrate interface on the electrical performance of the device is also inserted
International Semiconductor Conference, 2006; 10/2006
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ABSTRACT: Extensive numerical simulations have been carried out to compare the electrical performance of ideal Schottky diodes on diamond and silicon carbide. The influences of the drift layer parameters on the off-state behaviour of the diodes are presented for both punch-through (PT) and non punch-through (nPT) structures. In PT case breakdown voltage was shown to be constant with the drift doping at low concentrations. Analytical expressions of the breakdown voltage variation with doping for nPT diodes are also included
International Semiconductor Conference, 2006; 10/2006
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ABSTRACT: Nanoelectromechanical (NEM) devices were developed for memory. The concept of a switch unit employing carbon nanotubes (CNT) was extended to random access memory (RAM). The unique vertical structure of these nanotubes allows a high integration density for devices. The easy fabrication process can give a high yield and reliability to device
Custom Integrated Circuits Conference, 2006. CICC '06. IEEE; 10/2006
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ABSTRACT: Photovoltaic power generation is spreading all around the globe with increasing support from the public and governments. Among the obstacles yet to overcome are higher cell efficiency, lower cost, and longer lifetime. The latter is the focus of the research presented here as it provides an alternative photovoltaic ac module inverter with long lifetime. Four commercial inverters analyzed in our laboratory contained electrolytic capacitors whose lifetimes are limited to 12000 hours. In the proposed solution these components are obviated by using an energy control scheme that stores all the energy fluctuation in the dc-link polypropylene capacitor. The energy control strategy has been applied in a prototype power conditioning unit that comprises a phase-shift full-bridge dc-ac-dc converter connected in series with a current source inverter. The grid current magnitude is controlled using a proportional derivative compensator that maintains the average value of the dc-link capacitor at a voltage level of 475 V, while allowing oscillations with a peak value of 125 V. Simultaneously, a pulse-width-modulation integrated circuit controller maintains a steady dc voltage at the photovoltaic panel's terminals, hence enhancing the performance of the maximum power point tracking algorithm. The sinusoidal shape of the current injection is attained using current-mode-control. It is shown that the converter operates at high efficiency and that the energy fluctuation is absorbed at the dc-link capacitor. In addition, it is shown that the perturb and observe maximum power point tracking algorithm performs well over a day of variable irradiance conditions
Power Electronics Specialists Conference, 2006. PESC '06. 37th IEEE; 07/2006
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M. Brezeanu,
M. Avram,
S.J. Rashid, G.A.J. Amaratunga,
T. Butler,
N.L. Rupesinghe,
F. Udrea,
A. Tajani,
M. Dixon,
D.J. Twitchen,
A. Garraway,
D. Chamund,
P. Taylor,
G. Brezeanu
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ABSTRACT: A comprehensive study on the off-state performance of synthetic single crystal (SSC) diamond Schottky barrier diodes (SBDs) is the subject of this paper. Three termination structures suitable for unipolar diamond power devices are numerically investigated. Comparisons between the three terminations, based on blocking performance and area consumption are presented. Optimum design parameters derived from simulations are included for each structure. Experimental results of reverse-biased diamond SBDs for the first time with ramp angle termination are also presented
Power Semiconductor Devices and IC's, 2006. ISPSD 2006. IEEE International Symposium on; 07/2006
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W. I. Milne,
K. B. K. Teo,
M. Mann,
I. Y. Y. Bu, G. A. J. Amaratunga,
N. De Jonge,
M. Allioux,
J. T. Oostveen,
P. Legagneux,
E. Minoux,
L. Gangloff,
L. Hudanski,
J.-P. Schnell,
L. D. Dieumegard,
F. Peauger,
T. Wells,
M. El-Gomati
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ABSTRACT: Carbon nanotubes (CNTs) are a unique form of carbon filament/fiber in which the graphene walls roll up to form tubes. They can exhibit either metallic-like or semiconductor-like properties. With the graphene walls parallel to the filament axis, nanotubes (single wall metallic-type or multi-wall) exhibit high electrical conductivity at room temperature. This high electrical conductivity allied to their remarkable thermal stability has made CNTs one of the most intensely studied material systems for field emission (FE) applications. In this paper we will describe the growth of multiwall CNTs and their application in a range of field emission based systems including their use in SEM sources, emitters for use in microwave amplifiers and as emitters in field emission based displays (FEDs). (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Physica Status Solidi (A) Applications and Materials 04/2006; 203(6):1058 - 1063. · 1.46 Impact Factor
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L. E. Hueso,
G. Burnell,
J. L. Prieto,
L. Granja,
C. Bell,
D. J. Kang,
M. Chhowalla,
S. N. Cha,
J. E. Jang, G. A. J. Amaratunga,
N. D. Mathur
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ABSTRACT: The possibility of performing spintronics at the molecular level may be realized in devices that combine fully spin polarized oxides, such as manganites with carbon nanotubes. However, it is not clear whether electrical transport between such different material systems is viable. Here, we show that the room-temperature conductance of manganite-nanotube-manganite devices is only one-half of the value recorded in similar palladium-nanotube-palladium devices. Interestingly, the former shows a gap in the conductivity below the relatively high temperature of 200 K. Our results suggest the possibility of new spintronics heterostructures that exploit fully spin polarized sources and drains.
Applied Physics Letters 02/2006; 88(8):083120-083120-3. · 3.84 Impact Factor
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ABSTRACT: Various nano-devices based on vertical nanotubes were developed. Carbon nanotubes (CNTs) were employed as a functional part or a nano structure of a nanoelectromechanical (NEM) switch, nano-capacitor, and NEM-dynamic random access memory (DRAM). The unique vertical structure of nanotubes allows high integration density for devices.
Emerging Technologies - Nanoelectronics, 2006 IEEE Conference on; 02/2006
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ABSTRACT: Maximum power point tracking (MPPT) strategies are an essential part of photovoltaic (PV) power converters' control. These algorithms maintain the operation of the PV panel at the optimal point for maximum performance. In addition, the power converter must synchronise with the electricity grid and inject the power extracted from the PV panel. These two tasks are executed by the controller in the power conditioning unit. This, however, results in complicated control loops. Moreover, the interaction with the grid may cause stability problems in the power converter during voltage disturbances. The dynamic control of PV modules connected to the electricity supply presented by the authors provides a substantial improvement in power converter stability and ease of implementation. This strategy combines grid power injection control and PV MPPT into a single control block. The first objective is achieved using current-mode control to shape the current injection whereas the latter objective exploits the dynamic behaviour of the PV panel to determine changes in the grid current magnitude. An implemented prototype system shows the performance of the proposed strategy and the results are compared against commercially available inverters.
IEE Proceedings - Electric Power Applications 02/2006; · 0.55 Impact Factor
