High Current Conduction Research Articles

Package Limited Current Rating Test Methodology

The current trend in electronics is toward the use of power devices with higher current, smaller size and lower power dissipation. The requirement for power devices with compact size and high current conduction capability has increased tremendously in the past several years. In order to meet the market demanding, more and more new advanced package technologies such as PQFN with clip bond have been developed to reduce the package size while maintaining high current carrying capability. In the past, the maximum continuous current of a product with big package size such as TO220, TO252, TO263 and TO247 etc is limited by the silicon die itself. Along with more products are being developed into smaller packages such as PQFN/MLP, the maximum continuous current is becoming limited not by the silicon die but by the package instead, which we call it package limited current (PLC).

A Study on the Design and Electrical Characteristics Enhancement of the Floating Island IGBT with Low On-Resistance

Insulated Gate Bipolar Transistors(IGBTs) have received wide attention because of their high current conduction and good switching characteristics. To reduce the power loss of IGBT, the onstate voltage drop should be lowered and the switching time should be shortened. However, there is trade-off between the breakdown voltage and the on-state voltage drop. The FLoatingIsland(FLI) structure can lower the on-state voltage drop without reducing breakdown voltage. In this paper, The FLI IGBT shows an on-state voltage drop that is 22.5% lower than the conventional IGBT, even though the breakdown voltages of each IGBT are almost identical.

1,200 V급 Trench Gate Field Stop IGBT 소자의 전기적 특성 향상 방안에 관한 연구

IGBT (insulated gate bipolar transistor) have received wide attention because of their high current conduction and good switching characteristics. To reduce the power loss of IGBT, the on state voltage drop should be lowered and the switching time should be shorted. However, there is Trade-off between the breakdown voltage and the on state voltage drop. To achieving good electrical characteristics, field stop IGBT (FS IGBT) is proposed. In this paper, 1,200 V planar gate non punch-through IGBT (planar gate NPT IGBT), planar gate FS IGBT and trench gate FS IGBT is designed and optimized. The simulation results are compared with each three structures. In results, we optain optimal design parameters and confirm excellence of trench gate FS IGBT. Experimental result by using medici, shows 40% improvement of on state voltage drop.

High current conduction with high mobility by non-radiative charge recombination interfaces in organic semiconductor devices

We report a unique non-radiative p-n-p junction structure to provide high current conduction with high mobility in organic semiconductor devices. The current conduction was improved by increasing p-n junctions made with intrinsic p-type hole transport layer and n-type electron transport layer. The excellent hole mobility of 5.3×10−1cm2/Vs in this p-n-p device configuration is measured by the space charge limited current method with an electric field of 0.3MV/cm. Enhanced current conduction of 248% at 4.0V was observed in fluorescent blue organic light-emitting diodes with introduction of non-radiative p-n-p-n-p junction interfaces. Thereupon, the power efficiency at 1000cd/m2 was improved by 22% and the driving voltage also was reduced by 17%, compared to that of no interface device. Such high current conduction with high mobility is attributed to the carrier recombination at p-n-p interfaces through coulombic interaction. This non-radiative p-n-p junction structure suggested in this report can be very useful for many practical organic semiconductor device applications.

HTS Current Leads Prepared by the TFA-MOD Processed YBCO Tapes

HTS current leads have been prepared by the TFA-MOD processed YBCO tapes 5 mm in width and around 120 μm in overall thickness. The YBCO superconducting thin layer with 1.5 μm is formed on the oxide buffer layers deposited on Hastelloy substrate tape. The critical current of the YBCO tapes is around 100 A at 77 K in self-field. A current lead unit is composed of a GFRP board and five YBCO tapes soldered to Cu cap at both ends. The transport current of the ten current lead units ranges from 536 A to 408 A at 77 K in liquid nitrogen. The YBCO current lead is assembled from the ten current lead units in parallel. The transport current of 4,000 A at 77 K was stably carried with no voltage generation on the YBCO tapes of the assembled current lead for ten minutes. Furthermore, the trans port current of 5,000 A was successfully applied with voltage of around 200 μV on YBCO tapes. The heat leakage of the assembled YBCO current lead with 150 mm in length between 77 K and 4.2 K is estimated to be 470 mW. Therefore, the heat load of it at transport current of 4000 A corresponds to 0.12 W/kA, which is one order of magnitude smaller than that of conventional Cu current lead. The small heat load results from high current performance and low thermal conductivity in the present YBCO current lead.

Development of HTS Current Leads Prepared by the TFA-MOD Processed YBCO Tapes

HTS current leads have been prepared by the TFA-MOD processed YBCO tapes. A current lead unit is composed of five YBCO tapes soldered to Cu caps at both ends and a GFRP board. The YBCO tape is 5 mm in width, 190 mm in length and about 120 ¿m in overall thickness. The YBCO superconducting layer, 1.5 ¿m in thickness, is formed on oxide buffer layers of GZO and CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> deposited on Hastelloy substrate tapes. Transport current is supplied through Ag layer deposited on YBCO layer. The YBCO tapes with critical current of about 170 A at 77 K in self-fields have been used for two 500 A-class current lead units. The transport current of 800 A was stably carried in liquid nitrogen without any voltage appearance on each tape. The voltage between both Cu caps linearly increased with increasing current, and it was about 350 ¿V at 500 A. The low voltage at Cu joints results from low contact resistance between YBCO tapes and Cu caps, and causes small Joule heating at the Cu joints. Furthermore, the transport current of 1400 A was successfully applied in the current lead combined with two units in parallel. The heat leakage of the current lead unit composed of five YBCO tapes and a GFRP board between 77 K and 4.2 K is calculated to be 47 mW/0.5 kA, which is much smaller than that of conventional Cu current lead (1.2 W/kA). The small heat leakage results from high current performance and low thermal conductivity in the present HTS current lead.

Static dielectric constant of Al nanocrystal/Al2O3 nanocomposite thin films determined by the capacitance-voltage reconstruction technique

Al nanocrystal (nc-Al)/Al2O3 nanocomposite thin films were synthesized by radio-frequency magnetron sputtering. The static dielectric constant (εr) of the nanocomposite thin films was determined by the capacitance-voltage reconstruction technique which was able to correct for the influence of high current conduction in the thin films. In contrast to pure Al2O3, the nanocomposite has a much higher εr and its εr exhibits strong temperature dependence also. The higher εr is attributed to the dipole effect of the Al–O dangling bonds due to the presence of nc-Al in the Al2O3 matrix. However, the dipole effect degrades at a higher temperature, which explains the observed decrease in εr with increasing temperature.

트렌치 콜렉터를 가지는 새로운 TIGBT 에 관한 연구

Various power semiconductor devices have been developed and evolved since 1950s. Among them, IGBT is the most developed power semiconductor device which has high breakdown voltage, high current conduction and suitable switching speed which perform trade-offs between each other. In other words, there are trade-offs between a breakdown voltage and on-state voltage drop, and between on-state voltage drop and turn-off time. In this paper, the new structure is proposed to improve a trade-off between a breakdown voltage and on-state voltage drop. The proposed structure has a trench collector and this trench collector induces an accumulation layer at the bottom of an n-drift region during off-state. And this accumulation layer prevents expansion of depletion layer so that trapezoidal electric field distribution is performed in the n-drift region. As a result of this, breakdown voltage is increased without increasing on-state voltage drop. The electrical characteristics of the proposed IGBT is analyzed and optimized by using representative device simulator, TSUPREM4 and MEDICI. After optimization, the electrical characteristics of the proposed IGBT is compared with NPT IGBT which have the same device thickness. As a result of this, it can be confirmed that the proposed structure increases the breakdown voltage of 800 V than that of the conventional NPT IGBT without increasing the on-state voltage drop.

Electrical Trimming of Boron-Doped Polysilicon Nanofilm Resistors Deposited at Different Temperatures

The previous research showed that highly doped polysilicon nanofilms (PSNFs) have a high gauge factor and stable temperature characteristics, promoting their applications in piezoresistive sensors. For correcting the resistance deviation and improving the resistance matching of sensing elements, the electrical trimming (ET) characteristics of PSNFs deposited by LPCVD at different temperatures were studied. By the interstitial-vacancy (IV) model, the resistance falloff in trimming phenomenon is considered as a result of the decrease of scattering centers caused by the recombination of IV pairs. By modeling grain boundaries (GBs) as the accumulation of IV pairs (basic defects), it is believed that IV pairs can recombine layer-by-layer under the energy excitation of joule heat generated by high current conduction. The experiment results show that the threshold current density for ET of PSNFs is an order of magnitude lower than that of polysilicon common films, while the trimming accuracy and stability of directly deposited PSNFs are superior to the recrystallized ones. Finally, it is gained that reducing amorphous phases at GBs by optimizing deposition temperature can improve ET characteristics of PSNFs.

Thermal behavior of a superjunction MOSFET in a high-current conduction

In this paper, a detailed study of the superjunction MOSFET (SJ-MOSFET) thermal behavior on high-current conduction is presented. First, the heat-generation (HG) process and its dependence on device geometry and biasing conditions are elucidated from numerical-simulation tools. Later, the resultant temperature distribution is evaluated by simulation, thus, acquiring a physical understanding of its impact on the electrical characteristics and failure mechanisms, particularly at short-circuit operation. The obtained results show relevant differences with respect to the thermal behavior of conventional power MOSFETs. As a matter of fact, the maximum HG in SJ-MOSFET is found at a certain distance from the surface, which principally depends on the drift length. This fact has important implications on the device reliability prediction and a compact electrothermal modeling

An experimental study on effects of monopolar diathermy on the bile ducts.

To study the effects of monopolar diathermy on the bile ducts in pigs. Experimental study. University hospital, Norway. 18 pigs. Laparotomy, application of diathermy at standard sites along the cystic duct, the bile ducts, and a cystic duct containing a metal clip, 3 to 12 times of 5 seconds' duration at each site. Temperature was subsequently recorded at standard measurement points on the bile ducts. Twelve pigs were killed after three weeks for assessment of the bile ducts at necropsy. Increase in temperature in the bile duct walls and late changes in the bile ducts. Temperature increased by 4-6 degrees C during 6 of 330 diathermy applications along the cystic duct, by 4-18 degrees C in 8 of 126 applications along the common bile duct, and by 4-11 degrees C at the clip in 9 of 54 applications. There were no macroscopic or microscopic changes in the bile ducts. Monopolar diathermy induced unexpected distant increases in the temperature of the bile duct walls and at a clip on the cystic duct probably because diathermy current energy was distributed along channels of high current conductivity.

Resin-impregnated bulk RE–Ba–Cu–O current leads for the superconducting magnet on maglev train

Bulk RE–Ba–Cu–O (RE: rare earth elements) superconductors exhibit high critical current density ( J c) and low thermal conductivity, that are the characteristics desired for the current lead applications. In this study, we studied whether the resin-impregnated Y–Ba–Cu–O rods can be used as the current lead for the superconducting magnet on a magnetically levitated train. The fatigue test showed that the mechanical properties of resin-impregnated Y–Ba–Cu–O rods are sufficiently good for maglev applications. We could also pass the electric currents of 500 A without heat generation. This was further confirmed by field distribution measurements, which showed that the superconducting state of the current lead was well maintained when the currents of 500 A were passed.

Effects of high current conduction in sub-micron Ti-silicided films

Modeling and characterization of high current conduction in sub-micron titanium disilicide (TiSi 2) films formed on n +/p + silicon and n +/p + polysilicon over active or field oxide under DC stress are reported. High current conduction in TiSi 2 films is shown to be strongly affected by the fabrication technology and process conditions. A model has been developed to explain the self-heating effect of silicide films under high DC stress. A parameter B is used to describe the sensitivity of the films to high current conduction. We found that the parameter B is linearly related to the initial resistance of the film, the temperature coefficient of resistance of TiSi 2 and the thermal impedance of the surrounding structures, and the results agree well with the experimental data.

13 kA current lead with textured YBCO plates

At Haldor Topsoe A/S, the authors have developed a texturing process by which they produce YBCO high temperature superconductor plates with high current densities and low thermal conductivity suitable for current leads between 77 K and 4 K. In their design of such a lead, the superconductor is quench protected by a shunt with low heat leak and the brittleness of the YBCO material has been overcome by reinforcement. The lead has been tested by CERN and has fulfilled CERN's specifications concerning current capacity, total heat leak, contact resistances and quench protection of the superconductor.

Defect state assisted tunneling in intermediate temperature molecular beam epitaxy grown GaAs

Current transport in molecular beam epitaxy (MBE) GaAs grown at low and intermediate growth temperatures is strongly affected by defects. A model is developed here that shows that tunneling assisted by defect states can dominate, at some bias ranges, current transport in Schottky contacts to unannealed GaAs material grown at the intermediate temperature range of about 400°C. The deep defect states are modeled by quantum wells which trap electrons emitted from the cathode before re-emission to semiconductor. Comparison of theory with experimental data shows defect states of energies about 0.5 eVbelow conduction band to provide the best fit to data. This suggests that arsenic interstitials are likely to mediate this conduction. Comparison is also made between as-grown material and GaAs grown at the same temperature but annealed at 600°C. It is suggested that reduction of these defects by thermal annealing can explain lower current conduction at high biases in the annealed device as well as higher current conduction at low biases due to higher lifetime. Quenching of current by light in the as-grown material can also be explained based on occupancy of trap states. Identification of this mechanism can lead to its utilization in making ohmic contacts, or its elimination by growing tunneling barrier layers.

Studies on the effect of channel implantation on the drain current of a grooved-gate MOSFET

In a grooved-gate MOSFET with a U-grooved gate and a ion-implanted channel, the lateral concentration profile of the channel is non-uniform. This has a remarkable influence on the current-voltage characteristics of the device. An analytical model based on the non-uniform lateral concentration profile along the channel for a long-channel grooved-gate MOSFET has been developed to investigate the effects of the groove angle, dose and energy of the channel implantation and other groove dimensions on the electrical performance of the device. The simulation results demonstrates that if properly optimized, higher current conduction at a desired threshold voltage with improved breakdown voltage, as compared with a conventional MOSFET can be achieved. Experimental results from a fabricated test device structure support the simulated current-voltage characteristics based on the model.

Basic Discussion on Low Temperature Power Electronics

The low temperature power electronics are needed for the interface between the superconducting energy system and the conventional power system, since the latter has been developed for the high voltage and low current, and for the alternating current, while the former has been oriented for the high current and low voltage, and for the direct current. As for the power switching devices for the converter between ac(conventional technology) and dc(superconducting technology), we have experimented the semiconductor unipolar and bipolar devices and their models for the computer simulation have been derived. The unipolar devices among which power MOS FET's represent the capability of low loss and high density current conduction in the liquid nitrogen temperature, although in the liquid helium temperature the freeze out of carriers has been observed. However the bipolar devices have the problem of the freeze out of carriers in low temperatures. The computer simulation based on the derived model are in good agreement with the experimental results and the optimal design parameters have been discussed. The operation in the liquid nitrogen temperature of power switching devices will be well consistent with the high temperature superconductors which have been recently discovered.

Switching for electric rail guns

A single stage rail gun driven from an inductive energy store requires a direct commutation switch. The high current levels and long conduction times dictate a fresh approach to the switch. This paper examines the commutation event and describes a successful 500 kA direct commutation rail gun switch.

Bulk boundary conditions for injection and extraction in trap-free lifetime and relaxation semiconductors

Small-carrier perturbations close to the unperturbed bulk are analyzed which represent boundary conditions for the perturbations produced by injection and extraction in thick enough semiconductor samples. On this basis concentration contours for the strong-perturbation range can be qualitatively drawn and even numerically evaluated. The results allow for a clear distinction to be made between lifetime and relaxation behavior. There is also an intermediary regime between these, and within it a new kind of steady state with oscillations in space is proved to be possible for appropriately chosen currents. Two new conditions have also been evidenced for the high current conduction in the asymptotic range: "equality recombination" in the deep-lifetime case, and "unperturbed conductivity" in the deep-relaxation case. Necessary conditions for obtaining an increase in resistance through injection have also been outlined.

An investigation of the electrical breakdown of a plasma - electrode system

Electrical breakdown between a pair of electrodes immersed in a flowing plasma corresponds to the transition between low- and high-current conduction régimes and has been attributed to many causes. In the work reported here, which involved cold electrodes in contact with the plasma produced by an electromagnetic shock tube, it was found that the minimum breakdown voltage corresponded to an average electric field in the cathode sheath of about 2 MV cm−1 over a wide range of plasma conditions. This was probably adequate to initiate the formation of non-thermionic cathode spots, and the voltage-current characteristics in the high-current régime were consistent with a field-emission theory of this mechanism, originally suggested by Smy. Moreover, electric fields in the plasma, sheath thicknesses and mean free paths were such that alternative explanations of the high-current régime were reasonably eliminated.