Showing papers on "Breakdown voltage published in 1977"

The physics of zinc oxide varistors

Abstract: This paper presents a physical description of the action of ZnO varistors, which are complex ceramic bodies of ZnO grains sintered in an oxide flux; their conductivity is very low at low voltage, but becomes high after a certain breakdown voltage is reached. It is found that depletion layers in the ZnO adjacent to the intergranular layers of oxide flux are the principal barrier to conduction at low voltage. These depletion layers are formed because electron traps in the intergranular layer absorb electrons from the ZnO, and the oxide flux itself is found to be more conductive than the neighboring barriers; conduction within the flux is observed at low temperatures. Electrical breakdown is associated with the completion of trap filling in thin regions of the intergranular layer. This model is supported by a wide range of physical phenomena.

Influence of particles on AC and DC electrical performance of gas insulated systems at extra-high-voltage

Abstract: High-voltage breakdown measurements were made in two similar particle contaminated coaxial test systems, one with AC and the other with DC voltages. Information is presented on the effects of particle size, shape, and material for both SF 6 and N 2 gases at pressures up to 15 atm in a plain coaxial gap and a coaxial gap including a post-type support spacer. Particle motion and location were found to strongly influence insulation performance. Measured values of electric fields which lifted and drove the particles, so that they bounced vertically and laterally, compare favorably with calculated levels. Movement into the the higher stress region at the center conductor was correlated with the initiation of sparkover. These breakdowns could be at levels more than a factor of five lower than those obtained when contamination was not introduced. Large variations in breakdown voltage of as much as 3 to 1 encountered under DC correspond to conditions where particle motion could be restricted, presumably by corona discharge, to motion near the outer electrode. AC sparkover levels were typically at the lower limits of the DC range. Both free and attached particles on the dielectric spacer surface would trigger flashover at the same low levels as were measured in the gas gap.

Theory and breakdown voltage for planar devices with a single field limiting ring

Abstract: The use of one or more floating field limiting rings reduces the adverse effect of junction curvature on the breakdown voltage in planar devices. Although this has been known for some time, there has not been a way of accurately predicting the amount of improvement that can be achieved using field rings. In this paper, a computer algorithm is presented which makes it possible to perform field calculations on devices with floating field rings. In addition, a normalized curve is presented which shows the relative improvement that a single optimally placed field ring has on the breakdown voltage for any planar device. The basis of the construction of this curve is the use of a normalized radius of curvature which is a precise measure of the effect of curvature for any device. The theoretical predictions are compared with experiments for over 640 devices encompassing 16 different field ring locations. Good agreement is achieved between theory and experiment.

Influence of secondary‐electron emission from MgO surfaces on voltage‐breakdown curves in Penning mixtures for insulated‐electrode discharges

Abstract: Voltage‐breakdown curves in a Ne+0.1% Ar Penning mixture for insulated‐electrode discharges are strongly influenced by changes in the surface properties of a deposited MgO cathode. A model has been developed to calculate an effective secondary‐electron‐emission coefficient γ in Penning mixtures as a function of the insulator‐energy‐band parameters. Incorporation of the calculated γ into the breakdown criterion results in good agreement between calculated and measured voltage‐breakdown curves for differently prepared MgO cathode surfaces. The calculated results show that the value of γ for argon ions depends on the state of the MgO surface, and this occurs through a change in the width of the band gap of MgO. The results also show that a nonzero value of γ (Ar+) significantly lowers the breakdown voltages and changes the shape of the breakdown curves at higher values of P0d.

Junction termination extension (JTE), A new technique for increasing avalanche breakdown voltage and controlling surface electric fields in P-N junctions

Abstract: Extremely high breakdown voltages with very low leakage current have been achieved in plane and planar p-n junctions using an ion implanted junction extension for precise control of the depletion region charge in the junction termination. Theory is presented which shows a greatly improved control of both the peak surface and bulk electric fields in reverse biased p-n junctions. Experimental results show breakdown voltages better than 95% of the ideal and at lower leakage current than the corresponding unimplanted devices. For example, diodes with a normal breakdown voltage of 1050 volts with a .5ma leakage current become 1400 volt (1450 ideal) devices with a 5µa leakage current. Applications of the technique are feasible in MOS technology, as would be expected, but are even more attractive in power devices in which the dramatically reduced surface fields are just as important as the extremely high breakdown voltages since it means more flexibility in passivation techniques, two of which we have used to date. Our results have also shown that the implant can be at a variety of temperatures with a good degree of success, extra process flexibility being the goal of these tests.

Optimum design of triode-like JFET's by two-dimensional computer simulation

Abstract: Design criteria of triode-like JFET's are studied by fully utilizing two-dimensional numerical analysis. The current is caused by tlie carriers injected over a potential barrier in a depleted channel. In contrast to normal pentode-like FET'S, the drain field plays an important role reducing the barrier height and thus causing triode-like I-V characteristics. Triode-like characteristics depend strongly on device geometry. This operation can be realized only in short gate devices. The channel thickness a is an essential parameter in determining the operational mode. The devices operate as triodes or pentodes corresponding to thin or thick channels, respectively. If applied to low-resistance load direct-drive circuits, the mixed characteristics situated between the triode- and pentode-like ones, are more desirable when compared to pure triode-like ones, This is because of their low on-resistance and high ac power efficiency. The gate-drain distance l gd is also essential in determining breakdown voltage. The design criteria are discussed and an optimum design specified on the N D (channel doping)- a and N_{D} - l_{gd} planes with respect to triode-like characteristics, circuit application and breakdown phenomena. Calculated results are compared with experiments and good agreement is found without using any adjustable parameters. The present design criteria will be useful for designing triode-like JFET's.

Steady-State and Stability Analysis of Induction Motor Driven by Current Source Inverter

Abstract: Steady-state characteristics and instability of an induction motor driven by current source inverter are studied in comparison with the system driven by voltage source inverter. It is shown that as the speed is increased the electromagnetic torque takes three extremities a maximum torque is close to the standstill and a minimum and a second maximum torques are near to the synchronous speed. Thus the magnitude of the starting torque is slightly less than the breakdown torque and larger than that for the voltage source type. Operation close to the synchronous speed is impractical, because of the higher copper loss and lower efficiency due to the increase of current and the decrease of the power factor with increasing speed. As this fact prevails also in the negative slip region, a dynamic brake action rather than a regenerative braking action will be obtained. Over a wide range of slip, higher torques than those for the voltage source type are obtained. Instability appears usually as a sustained oscillation on armature voltage and current. Applying the Routh-Hurwitz criterion, several instability boundaries for various parameters are described. Some experimental results are presented which show essential agreement with the theory.

The importance of insulator properties in a thin-film electroluminescent device

Abstract: AC-coupled thin-film electroluminescent devices employ insulating layers to limit the current density through the active layers. The requirements and limitations in driving such devices are then dependent upon the properties of the dielectric layers. We define an external efficiency for an ac thin-film electroluminescent device and consider two limiting cases, current response 1) fast, and 2) slow, compared to an applied voltage change. Relationships are then derived among external efficiency, relative luminance, and the two principal characteristics of the insulating layer, specifically charge density at breakdown and thickness. It is shown, for example, that charge density at breakdown for the insulators should be at least three times the corresponding quantity for the active layer.

Experimental study of breakdown voltage-time characteristics of large air gaps with lightning impulses

Abstract: This study reports mainly two points about the breakdown voltage - time characteristics of 1 - 5 m rod-plane and rod - rod gaps with lightning impulses. It is shown, at first, that the breakdown time follows the logarithmic normal distribution with a constant impulse level and that the probability of the breakdown time can be determined by empirical equation from the mean breakdown time and its standard deviation. The second part covers the breakdown phenomena with lightning impulses, delineating the development of streamers and leaders in relation to breakdown time. Estimates on basis of breakdown processes are made to breakdown time with impulses of short tail waves.

High beta, high frequency transistor structure

Abstract: High beta, high frequency transistors require very narrow and high resistance base structures, thereby placing a low limit of collector-emitter voltages that may be used without encountering "punch-through" breakdown. This invention permits the use of normal collector-emitter voltages without danger of punch-through problems by injecting into the high resistance base material an impurity grid that serves both as an electrostatic shield to increase the voltage breakdown level, and as a means of reducing the apparent lateral base resistance, thereby further increasing the high frequency capability of the device without degrading the high beta characteristics.

Grooved Gate MOSFET

Abstract: Grooved Gate type MOS FET's which realize a short channel device with high punch-through breakdown voltage and little threshold voltage (VT) fluctuation, are fabricated by using a promising photoresist technique. A proposed, self-aligned gate MOS FET structure (Grooved Gate MOS FET) is based on two-dimensional analyses of short channel devices. A characteristic feature of the device is negative source and drain junction depth. The fabricated 21 stage ring oscillator displays a high circuit performance for delay and power product of 0.12 pJ.

Over voltage protective device and circuits for insulated gate transistors

Abstract: Protective devices and circuits for insulated gate transistors are improved by another p/n junction diode or MOS diode preventing breakdown of the thin oxide of the protective device. The breakdown voltage of the protective device or p/n diode may be tailored to a preselected voltage by altering its metallurgical junction by ion implantation or other techniques. Tailoring permits the breakdown voltage of the protective device to be independent of process and circuit specification of a protected or internal circuit. A plurality of parallel circuits connected as a protective device limits or controls secondary breakdown of the protective device.

The breakdown voltage and discharge extension of long gaps in nitrogen‐SF6 and air‐SF6 gas mixtures

Abstract: The breakdown voltage and the extension of the discharge has been investigated for impulse voltages with rod‐plane gaps of 30 and 50 cm in nitrogen‐SF6 and air‐SF6 mixtures at atmospheric pressure. The addition of 0.4–2% SF6 by volume to nitrogen reduced the 50% breakdown voltage V50 for both polarity impulse voltages below the value for pure nitrogen or pure SF6, typically 50% below the pure SF6 level. However, in air‐SF6 mixtures the opposite effect was found, and a small addition of SF6 (e.g., 1%) increased V50 by typically 80% above that for pure SF6. The extension of the breakdown path has been studied with an image converter and still cameras. In nitrogen‐SF6 mixtures there was a rapid extension of the discharge corresponding to the condition of the minimum breakdown voltage with the 2% SF6 content. The typical discharge extension characteristic in both types of mixtures was an intermittent propagation of the leader accompanied by ball‐like regions of corona streamers at the leader tip. For a 50% SF...

Method of increasing field inversion threshold voltage and reducing leakage current and electrical noise in semiconductor devices

Abstract: A method for processing a semiconductor wafer to reduce electrical noise, to reduce the surface component of junction leakage current, to increase junction reverse breakdown voltage, and to increase field inversion voltage. Subsequent to last high temperature processing to which the semiconductor wafer is exposed in course of its manufacture, the semiconductor wafer is subjected to an annealing cycle in an inert ambient at a temperature in the range of 600 to 950 degrees Centigrade. At this point the semiconductor wafer has a field oxide thereon produced by prior processing operations. The annealing cycle stabilizes the semiconductor device by allowing an oxide-semiconductor interface region of the wafer to attain a minimum energy configuration, thereby reducing the surface-state charge density. The semiconductor wafer is then exposed to an oxidizing ambient for a short time to increase the oxide charge. At the end of the oxidizing procedure, the wafer is quenched to prevent reduction of the oxide charge by diffusion of the oxidizing species which create the oxide charge. The increased oxide charge increases the field inversion voltage. The semiconductor wafer is thus again subjected to an inert ambient, for restabilization. The semiconductor wafer is then subjected to a low temperature annealing cycle in a hydrogen ambient at a temperature in the range from 300 to 500 degrees Centigrade. The low temperature annealing step reduces the surface-state charge density without substantially decreasing the density of the oxide charge trapped in the field oxide, and therefore does not substantially lower the field inversion voltage.

Drift of the breakdown voltage in p-n junctions in silicon (walk-out)

Abstract: A quantitative model for the time behaviour of the walk-out phenomenon in planar p - n junctions is given. The injection of hot carriers into SiO 2 and subsequent trapping of part of them is assumed to be the origin of the walk-out. The model is found to be in reasonable agreement with the experimental results on both p + − n and n + − p junctions. The parameters in the model are discussed in relation with the experiments.

Semiconductor device having a high breakdown voltage junction characteristic

Abstract: A semiconductor device having a p-n junction characterized by low electric field crowding and a resulting high avalanche breakdown voltage requirement. The semiconductor device is comprised of a semiconductor substrate having impurity atoms of one type and a first surface. A first doped region lies in said substrate at said first surface and has dopant atoms of a type opposite to said one type. A second doped region lies in said substrate at said first surface adjacent the entire perimeter of said first doped region. The second doped region extends laterally away from said first doped region, and has dopant atoms of the same type as and of less density than said dopant atoms of said first doped region.

Semiconductor switching element

Abstract: PROBLEM TO BE SOLVED: To control the high breakdown voltage and large current of a semiconductor switching element by forming a second-conductivity semiconductor layer which is connected with a source electrode between adjacent well layers, and making the total content of impurities in the semiconductor layer smaller than those of impurities in the well layers. SOLUTION: In a parallel-plate single-crystal silicon carbide semiconductor substrate 1 having main surfaces on its top and bottom sides, a low-resistance n+-type drain layer 2 and an n--type drift layer 3 having higher resistance than the layer 2 has are laminated upon another. A plurality of high- concentration p+-type well layers 41 is provided in the drift layer 3 from one main surface of the substrate 1 and a high-concentration n+-type source layer 5 and a p--type layer 10 containing impurities at a total content which is lower than that of impurities in the p+-type well layer 41 are formed in each p+-type well layer 41. The p--type layer 10 is brought into contact with the p-type well layers 41 on both sides. Consequently, the switching of a switching element provided with a voltage clamping function under a high-breakdown voltage and large-current condition can be inhibited.

Flashover breakdown of an insulator in vacuum by a voltage impulse in the presence of a magnetic field

Abstract: The flashover strength of Plexiglas insulators subjected to submicrosecond voltage impulses in vacuum and in the presence of a magnetic field that is perpendicular to the insulator surface is studied. Flashover breakdown strength is reduced by magnetic fields of a few kilogauss. Observation by fast‐framing photography does not reveal curvature of the breakdown arc greater than 20°.

The influence of recombination center data on the I‐V characteristics of silicon p+‐i‐n+ diodes

Abstract: Calculations have been made of dc I‐V characteristics of long p+‐i‐n+ diodes with deep levels showing a negative differential resistance region. The influence of the recombination center data, especially of the capture coefficients of both electrons and holes, cn and c−p, is discussed. The calculations show that cn only influences the high injection regime and the minimum voltage, whereas c−p only influences the prebreakdown region and the breakdown voltage; thus a new method arises to determine cn and c−p in the same sample. These results are confirmed in silicon p+‐i‐n+ diodes with the gold acceptor acting as recombination center. Theory and experimental results are in complete agreement for cn=3.2×10−8 cm3 s−1 and c−p=1×10−7 cm3 s−1. Finally, these values are compared with those given in the literature.

Testing of typical spacecraft materials in a simulated substorm environment

Abstract: The test specimens were spacecraft paints, silvered Teflon, thermal blankets, and solar array segments. The samples, ranging in size from 300 to 1000 sq cm were exposed to monoenergetic electron energies from 2 to 20 keV at a current density of 1 NA/sq cm. The samples generally behaved as capacitors with strong voltage gradient at their edges. The charging characteristics of the silvered Teflon, Kapton, and solar cell covers were controlled by the secondary emission characteristics. Insulators that did not discharge were the spacecraft paints and the quartz fiber cloth thermal blanket sample. All other samples did experience discharges when the surface voltage reached -8 to -16kV. The discharges were photographed. The breakdown voltage for each sample was determined and the average energy lost in the discharge was computed.

Gate controlled diode protection for drain of IGFET

Abstract: An integrated circuit includes an insulated-gate field effect transistor and a protection device coupled to either the source or drain of the transistor. The protection device includes a gate-controlled diode having a breakdown voltage that is less than the breakdown voltage of the drain of the field effect transistor.

The metal-overlap laterally-diffused (mold) Schottky diode

Abstract: A novel uniform-field/breakdown structure is described consisting of a planar metal-overlap laterally-diffused (MOLD) Schottky diode. This structure has been demonstrated to be free of edge breakdown by numerical two-dimensional calculations. Experimentally obtained aluminum-silicon MOLD Schottky diodes have shown near-ideal characteristics in terms of breakdown voltage, reverse I–V characteristics and forward I–V characteristics. The barrier height determined from forward current measurements (zero-volts intercept and activation-energy plot) is 0.74 V.

On the polarity effect of the breakdown voltage for dielectric liquids in an inhomogeneous field

Abstract: The polarity difference of the breakdown voltage of some pure dielectric liquids and transformer oil is qualitatively explained by analysing the electric field distribution of a point-plane test cell under the condition of unipolar injection of charge carriers. Although the space charge reduces the electric field at the point, it leads to an increase in the stressed volume thus increasing the probability of breakdown. The magnitude of the space-charge contribution is inversely proportional to the mobility of the injected charge carriers. Since in some of these liquids electrons exhibit a much higher mobility than positive ions, the influence of the space charge is reduced for the point negative compared with the point positive.

Short-channel V-groove complementary MOS device

Abstract: An improved short-channel complementary MOS transistor structure is provided. The problems of low punch-through voltage breakdown, and "short-channel effects" are particularly addressed and solved. Accurate and precise field protection of all area surrounding the channel, source and drain regions of both the p-channel MOS transistor device and the n-channel transistor device is simply and effectively accomplished. The threshold voltage of the n-channel MOS transistor device is precisely controlled by a boron implantation. The method of manufacturing such device is disclosed.

Low Voltage Firing Characteristics of a Simple Triggered Vacuum Gap

Abstract: The firing characteristics of the simple triggered vacuum gap (TVG) using lead zirconate titanate as dielectric material in the triggered gap are described. This TVG has a long life of about 2000 firings without appreciable deterioration of the electrical properties for main discharge currents upto 3 kA and is much superior to these made with Supramica (Mycalex Corporation of America) and silicon carbide as used in our earlier investigations. The effects of the variation of trigger voltage, trigger curcit, trigger pulse duration, trigger pulse energy, main gap voltage, main gap separation and main circuit energy on the firing characteristics have been studied. Trigger resistance progressively decreases with the number of firings of the trigger gap and as well as of the main gap. This decrease in the trigger resistance is more pronounced for main discharge currents exceeding 10 kA. The minimum trigger current required for reliable firing decreases with increase of trigger voltage upto a threshold value of 1.2 kV and there-onwards saturates at 3.0 A. This value is less than that obtained with Supramica as dielectric material. One hundred percent firing probability of the TVG at main gap voltages as low as 50 V is possible and this low voltage breakdown of the main gap appears to be similar to the breakdown at low pressures between moving plasma by other workers. and the cold electrodes immersed in it, as reported

A statistical approach to the streamer breakdown criterion in SF 6

Abstract: The electrical breakdown field strength in SF 6 calculated from measurements has been found to deviate considerably from the values predicted by the theoretical models used up to now. The simplest form of the streamer criterion predicts breakdown to take place at field strength - to - pressure ratios close to 8.9 kV/mm atm. The streamer model can be enhanced by introducing surface roughness and electrode curvature factors, thus explaining some of the experimental results obtained. The model is, however, unable to explain the general dependence of the breakdown field strength on parameters as pressure, electrode area and voltage waveform. This paper gives a new theoretical model for impulse breakdown in SF 6 , using a statistical approach to the streamer breakdown criterion. Field emission is assumed to be the source of primary electrons. This model gives correspondence with the experimental results for different electrode configurations covering a wide range of pressure and electrode area.

Low voltage varistor configuration

Abstract: Metal oxide varistor structures having a low breakdown voltage, low leakage current, high values of alpha, operational stability, and methods of making the same are disclosed. In accordance with one embodiment of the invention relating to metal oxide varistor structures, at least one of the planar surfaces of a varistor disk, for example, is provided with a recessed region for increasing the electric field intensity in the region of the recess and hence reducing the breakdown voltage of the varistor disk without altering the structural integrity of the disk. Methods for making varistor structures with one or more recesses on one or more surfaces of the varistor structures are also disclosed.