Showing papers on "Breakdown voltage published in 1972"

Triggering phenomena in avalanche diodes

Abstract: The operation of a small area p-n junction diode above the breakdown voltage is analyzed A new formulation in terms of ionization probability is used to derive the rate of turn-on of current in such structures Two differential equations are given which may be used to compute the probability that a carrier swept into or generated within the space-charge region triggers avalanche breakdown For a 27-V n+-p diode biased 1 V above breakdown, this probability is close to 05 for an electron entering from the p side, or 01 for a hole entering from n side Experimental measurements are in good agreement with the theoretical predictions

Surface breakdown in silicon planar diodes equipped with field plate

Abstract: The distribution of the electrical potential around the edge of the field plate in a silicon planar diode has been solved by means of a computer. The breakdown voltage related to this region has been derived as a function of impurity doping in silicon and of oxide thickness. If the oxide layer is not thick enough, avalanche breakdown voltage is often considerably lower than the value allowed by the material. The effect of Q ss has been found to be negligible. Breakdown voltage vs. gate voltage measurement on gated diodes and avalanche light emission support an edge breakdown mechanism. Breakdown voltage on field plated diodes matches rather well with the calculated values. It normally drifts towards higher values and during this walkout a hot carrier current is collected by the field plate. The field plate current is fairly proportional to avalanche current and increases with bulk doping. A new planar diode structure suitable for a BV up to 900 V has been designed. The discharge voltage in air between field plate and equipotential ring (EQR) is shown to be correlated with the actual field at the edge.

Effect of Conducting Particles on AC Corona and Breakdown in Compressed SF6

Abstract: This paper describes studies of the effects of conducting particles on breakdown phenomena in compressed SF6 under alternating voltage conditions. Results with free particles of different shapes and materials are compared with those obtained with fixed particles for both parallel-plane and coaxial electrode geometrics. Calculations of the particle motion and of the energy in microdischarges between particle and electrodes are used to suggest mechanisms by which breakdown is initiated. It is shown that the breakdown voltage, which can be as low as 10% of the uncontaminated value, is markedly dependent on particle shape, size and material, and that the nature of the motion in alternating fields is important in establishing conditions for free- particle-triggered breakdown.

The mechanism of spark breakdown in nitrogen, oxygen and sulphur hexafluoride

Abstract: An image converter and a 4-stage image intensifier have been used to investigate the development of spark breakdown in a 3-cm, uniform-field, gas-discharge gap. The growth of ionization, initiated by a burst of electrons a t the cathode, has been observed for overvoltages up to 25 % in nitrogen, oxygen and sulphur hexafluoride a t pressures in the range 13 to 40kPa (100 to 300 Torr). In nitrogen, time resolved shutter and streak records have been obtained which demonstrate, that, at low overvoltages, breakdown is preceded by the formation of a diffuse glow discharge whereas, at voltages well in excess of the static breakdown voltage, the arc discharge is formed directly in the track of the initial electron avalanche, as a result of space-charge distortion of the applied electric field. This change with overvoltage has previously been ascribed to a transition from a Townsend to a streamer breakdown mechanism; the present results, however, do not entirely support this view. In oxygen and sulphur hexafluoride, no such change in the form of ionization development has been observed and it is concluded from the evidence obtained that, even a t very small overvoltages, the development of ionization is strongly affected by space-charge distortion of the applied field. Photographs obtained in sulphur hexafluoride have been correlated with measured formative-time-lag data showing the time-lag-free region reported previously by Kuffel. Some conclusions have been drawn regarding the breakdown mechanism under these conditions.

Enhancement of breakdown properties of overlay annular diodes by field shaping resistive films

Abstract: Breakdown voltage of oxide masked and passivated overlay annular diodes are limited in magnitude and stability by locally high fields in the surface junction region. Topologically, it is demonstrated that these high field regions are influenced by both the overlay radius of curvature and the overlay to annular ring spacing. Breakdown voltages approaching bulk values are achieved only with much reduced average surface fields, requiring excessive area. The use of a highly resistive but essentially ohmic film over the oxide in the high field surface region can shape and homogenize the surface fields. The use of 2000 A polycrystalline silicon layers with sheet resistances in excess of 10 10 Ω/□ for the field shaping element is shown experimentally to lead to reduced surface spacings for a given breakdown voltage and less tendency for surface arcing.

Flashover across polyethylene and tetrafluoroethylene surfaces in vacuum under direct, alternating and surge voltages of various waveshapes

Abstract: Investigations were made of various factors which affect the flashover values across polyethylene and tetrafluoroethylene surfaces in vacuum. The factors studied included sample conditioning under sustained direct and power frequency voltages, and the effect of surge voltage waveshape. The breakdown values for a given voltage waveshape increased with the time of conditioning up to a maximum value which then remained constant within about 10%. Alternating voltages were found to be more effective in the conditioning process. The average breakdown voltage for each insulator decreased with increasing the surge front duration from 1 μs to about 150 μs and thereafter remained constant.

Semiconductor devices with diffused platinum

Abstract: A semiconductor device having platinum dispersed throughout said device. The dispersion of platinum within a semiconductor device results in improved electrical characteristics of the device. In a silicon diode, the improved characteristics include the reduction of reverse recovery time and an increase in the breakdown voltage. In a silicon transistor, the improved characteristics include the achievement of high switching speeds while maintaining high forward current gain.

Triple diffused high voltage transistor

Abstract: A high voltage transistor with improved surge voltage capacity is formed in a silicon semiconductor body of thickness of at least 4 mils and having two opposed major surfaces and a resistivity of at least 30 ohm-centimeters. A collector region adjoins a major surface and is comprised of three portions: The first collector portion adjoins a PN junction and has a substantially uniform dopant concentration therethrough corresponding to the resistivity of the body to support a desired reverse breakdown voltage. The second collector portion adjoins the major surface and has a dopant concentration of at least 1 X 1019 atoms per cubic centimeter at said surface and a steep dopant concentration gradient to provide for good ohmic and thermal contact properties. The third collector portion is intermediate the first and second collector portions and has higher dopant concentrations than said first collector portion, but lower than said second collector portion, and has a shallower dopant concentration gradient that said second collector portion to support a reverse breakdown surge voltage through the transistor. Preferably the transistor is the PNP type made by simultaneously diffusing boron and gallium and/or aluminum into the major surface of a silicon wafer or body having a given concentration level of N-type dopant therethrough. Thus the various portions of the collector region are simultaneously formed.

Voltage-Current Characteristics During Propagation of a Surge Breakdown of a Point-to-Plate Gap with Insulating Barrier

Abstract: A solid insulating barrier in a point-to-plate gap is a useful means for raising the positive flashover voltage. This paper examines the voltage-current-characteristic during positive and negative surge breakdown in air of the so-called barrier arrangement. The model used has a strike distance of 6 cm and a barrier of various dimensions. Photographs detail the discharge propagation. The flashover voltage depends upon position, thickness, and size of the barrier. Voltage stages of relatively constant value, lasting up to 30 Ms, suggest additional application as, surge protective device.

Recurrent arc heating process

Abstract: Gas or fluid flows through a gap between electrodes having an arc therebetween at a very high velocity while a system voltage is continuously maintained sufficient to cause breakdown at the gap. The high velocity gas elongates the arc until the arc voltage required for electrical conduction exceeds the breakdown voltage of the gap whereupon sparkover occurs in the gap, the arc being thereafter elongated again by the gas passing through the gap until the voltage required to sustain arcing exceeds the breakdown voltage of the gap, the cycle of gap breakdown and elongation being repeated over and over again. The greatly extended arc provides for more efficient heating of the gas, better mixing and a more uniform temperature to which the gas is heated.

Terminal for electrical apparatus with conductors cooled down to a low temperature

Abstract: A high voltage-resistant, current feed terminal to a superconductor cooled down to a low temperature, with its connected normal conductor being provided with a heat exchanger. Coolant input lines and coolant output lines each form spirals having turns which surround the normal conductor and which are designed as voltage dividers. The spiral-shaped design has the advantage that the coolant line can take up a high potential gradient. The voltage divider causes a uniform division of the voltage in such a manner that the breakdown voltage of the coolant is not reached.

The electrical breakdown of solid dielectrics in non-uniform fields

Abstract: The electrical breakdown of KBr, polyethylene and polymethylmethacryalate in non-uniform fields is considered. The observed breakdown voltage polarity effect, previously considered anomalous to current theories in which breakdown is governed by attainment of critical conditions at the cathode, is shown to be compatible to such theories if the effect of negative space charge within the dielectric is taken into account. It is proposed that the negative space charge arises through trapping of electrons, which are emitted into the dielectric at zero applied voltage owing to workfunction differences between the electrode and the dielectric.

High voltage capacitor assembly

Abstract: A high voltage capacitor assembly includes a ceramic body formed with a plurality of ceramic elements and embedded with interior electrodes which act to reduce the uneven potential distribution, which is often concentrated around the periphery of each of the exterior electrodes provided on both end faces of the ceramic body, thereby providing a capacitor assembly with an improved breakdown voltage characteristic.

High intensity lamp containing arc extinguishing base

Abstract: A high intensity lamp comprising an arc tube containing metal vapor such as sodium and mercury mounted within an evacuated single-ended outer jacket provided with a screw base. The use of high circuit voltage and high voltage starting pulses in conjunction with a vacuum jacket make the lamp especially susceptible to breakdown. Insulating refractory sleeves are provided about the inleads within the base which increase the breakdown voltage. However should an arc form, the ends of the inleads ball-up and withdraw into the sleeves and the arc is thereby constricted and extinguished.

Filamentary Thermal Breakdown in Thin Dielectrics

Abstract: A model of the breakdown of thin dielectric films is presented in which breakdown can result from thermal effects following a nondestructive electron avalanche. It is proposed that the avalanche leads to the generation of sufficient heat in a narrow channel for the ordinary electrical conductivity of the channel to be raised to a level at which thermal runaway could start, thus leading to destructive breakdown in a narrow region of the dielectric. The effects, on the time required for breakdown to occur, of input power, heat dissipation, and initial temperature rise caused by the avalanche are computed.

Vacuum breakdown and its effect on subsequent current emission

Abstract: The breakdown potential of ultrahigh-vacuum (10−9 torr) gaps has been measured using aluminium electrodes. The breakdown voltage increases linearily from 2.8 to 41.4 kV in the gap range 0.07–0.76 mm. The enhanced critical breakdown field is found to be (5.7 ± 1.7) × 109 V/m, in reasonable agreement with the recent theoretical prediction of Chatterton. For gap separations larger than, 0.89 mm, a large increase in the prebreakdown current, at a particular applied voltage (ignition), is observed. The enhanced electric field at the cathode during the ignition is found to be (2.4 ± 1.0) × 109 V/m over the gap separation 0.89–3.04 mm. The current before the onset of the breakdown is found to increase with increasing number of sparkings, in qualitative agreement with theory. The effects of repeated sparkings on both the ignition voltage and the enhancement-field factor are also studied over a wide range of electrode separations.

Moat-etched Schottky barrier diode displaying near ideal I–V characteristics

Abstract: A simple fabrication technique for Schottky diodes allows achievement of high breakdown voltage without sacrifice of speed at any current level. We have found the reverse blocking voltage of a Schottky diode can be increased to 80–90% of the bulk breakdown voltage of the silicon wafer by moat-etching into the wafer before deposition of the barrier metal. The moat-etched device exhibits the low leakage current and high reverse breakdown voltage characteristic of a guarded Schottky diode, but retains the fast switching speed of a planar device. In addition, it is observed that the moat-etched diode exhibits a lower barrier height than conventional planar or guarded structures so that a smaller junction area is required for given forward current in the moat-etched device. Junction areas as large as 0.11 cm 2 have been investigated.

Groove Detectors from High-Purity Germanium

Abstract: Detector have been fabricated from pure germanium with a lithium diffused N+ contact, and a P+ contact which is ion implanted in a dc glow discharge in boron trifluoride. A deep groove is used to increase the breakdown voltage. Measurements of the current-voltage characteristics of these detectors after temperature cycling are reported. The correlation of smooth etch pits with severe trapping in pure germanium detectors is shown. Finally, the performance of a few large detectors is given.

Temperature insensitive doped amorphous thin film switching and memory device

Abstract: This invention relates to a semi-conductor switching and memory device having a threshold or breakdown voltage which is relatively insensitive to environmental temperatures which range from approximately -35* to 130*C. and nuclear radiation after exposure to 1.3 X 1017 n/cm. In addition to the temperature insensitivity and radiation hardness characteristics of the present invention, the device exhibits a symmetrical positive and negative voltage limiting or voltage regulating phenomena in its ''''off'''' state current-voltage characteristic and also exhibits in its memory mode a very short setting and resetting time. The present device has a doped chalcogenide amorphous thin film material positioned adjacent two electrodes. The semi-conductor is deposited on an insulating substrate which is fixedly held in a sealed, nitrogen containing ''''flat pack'''' type ceramic container. The electrodes of the semi-conductor are electrically coupled to hermetically sealed electrical terminal feed-throughs of a container.

Overvoltage protection circuit

Abstract: A D.C. power supply generally includes a regulator to establish a selected output voltage, and an overvoltage protector circuit which protects the power supply loads in the event of a regulator malfunction. This disclosure includes two overvoltage protection circuits which utilize like protective methods. An overvoltage protector for a single low voltage supply includes a programmable unijunction transistor with a gate reference obtained from the temperature compensated reference within the voltage regulator, and triggered by the overvoltage condition appearing between its anode and cathode terminals. As such, this circuit is a three input circuit consisting of external references, monitored input and common. An overvoltage protector for high voltage dual supplies includes a temperature stable silicon unilateral switch that monitors part of the protected output and is triggered by an increase of that stabled voltage beyond the breakdown voltage of the device itself. As such, this circuit is a two input circuit requiring connection to monitored input and common. In both applications, low or high voltage, the voltage sensitive device triggers one or two silicon controlled rectifiers located across the monitored voltage outputs, thereby causing them to short out and to actuate the power supply''s respective current responsive safety devices.

Non-Destructive Screening for Thermal Second Breakdown

Abstract: The feasibility of developing nondestructive screening techniques to determine the second breakdown vulnerability of semiconductor devices at submicrosecond pulse conditions has been demonstrated. In addition, it has been shownl that second breakdown can be nondestructively initiated under certain current limiting conditions without causing degradation in device operating characteristics or device second breakdown vulnerability level to subsequent pulses of electrical energy. A low energy current impulse damage mechanism at second breakdown initiation has also been observed. The experimental investigations were performed using 1N4148 diodes fabricated with various junction areas and a fixed diffusion depth. The complete results of this work are documented in Reference 1.

Junction-temperature measurement of IMPATT diodes

Abstract: The breakdown voltage VB of an IMPATT diode is a function of the junction temperature. Pulse techniques are applied to measure VB directly during actual operation, thus giving the temperature within an accuracy of a few per cent. The method also provides a display of 'space-charge resistance at the operating temperature.

Voltage dependent phase switch

Abstract: A voltage dependent phase switch comprising a pair of transistors and a zener diode. An input signal is connected in series through the zener diode to drive the base of one of the transistors. The input signal is also connected to the base drive of an emitter follower transistor. When the input signal is negative and less in magnitude than the breakdown voltage of the zener diode then the emitter follower transistor is driven and an output signal is provided therefrom that increases linearly with increase in the input signal. However, when the input signal is negative and greater in magnitude than zener diode breakdown voltage then the transistor that is connected to the zener diode is driven and the voltage output decreases linearly with the increasing negative input voltage thereby providing a voltage dependent phase switch. In another embodiment of the invention an input signal circuit is provided which includes a DC source, a pulse generator and a sinusoidal signal generator wherein the currents are additive and provide a switching function in conjunction with the voltage dependent phase switch where the output sinusoidal signal is in-phase or 180 DEG out of phase with the sinusoidal signal generator signal depending upon the state of the pulse generator.

Field distribution near the surface of beveled P-N junctions in high voltage devices

Abstract: Experience with beveled p-n junctions does not fully agree with the predictions of Davies and Gentry. Specifically no optimum negative angle as claimed by Huth and Davies was found. A new method for determining the form of the space charge region near the surface shall be presented which avoids the insufficiencies of the model cited. Apart from more accurate results, this paper gives insight into an entirely new phenomenon. In contrast to conventional theory p-n junctions with small negative bevel angles exhibit an absolute electric field maximum underneath the surface. This effect causes a reduction of the breakdown voltage even when the electric field on the surface is sufficiently small. Results will be presented which show the dependency of the absolute field maximum on bevel angle, doping profile and material resistivity. It will be shown that a limit for the use of negative bevel angles exists at about 4 kV breakdown voltage. These theoretical predictions are in excellent agreement with potential probing experiments. Results will also be presented on the influence of dielectrics or charges on the surface.