Influence of the position of a long air gap on breakdown voltage for a positive long-front impulse voltage

The change in the breakdown of a long air gap corresponding to the damage in the gap's distance from an earth plane when a long-front impulse voltage is applied to the gap was examined. The results of this experiment lead to the generalization of conventional breakdown characteristics of a long air gap.     

Negative-impulse breakdown in compressed air

The negative-impulse breakdown voltage (b.d.v.) of a point-plane gap in compressed air shows, for sufficiently long gaps, the existence of a critical pressure, as in the case of positive polarity. The b.d.v. at any pressure also depends on the wavefront duration of the impulse voltage. When the wave-front is varied over a range of 1?210?s, a maximum b.d.v. is obtained for front times of 78?s and 7.5?s for a gap of 25.4 mm and 50.8 mm, respectively.     

Pulsed-r.f. slot-antenna breakdown in air

The formative time lag for pulsed-r.f. breakdown in dry air has been systematically measured as a function of gas pressure and antenna power level. A 0.4×0.9in slot was operated in the X band with powers ranging from 1 to 18kW and pressures ranging from 0.5 to 60torr.     

Vacuum breakdown at a ceramic surface in a microwave cavity

A series of tests on titanium dioxide (titania) is reported. A surface breakdown strength in excess of 60 kV/cm was established. A bond, formed by evaporating a thin film of aluminium onto the titania surface, proved successful in eliminating breakdown initiated at metal-ceramic contacts.     

The effect of ionizing radiation on the breakdown of large gaps in air

The influence of gamma radiation on the breakdown of a point-plane gap has been studied using impulse voltages of short and long wavefronts. Scatter of breakdown of some gaps is reduced by a factor of two and the mean breakdown value is reduced by a few percent.     

Calculated microwave breakdown voltages in nitrogen,oxygen and air from DC data

The general microwave breakdown characteristic in nitrogen, oxygen and air is calculated from the DC dependence of the rimary ionization coefficient and the electron mean energy on the reduced electric field using basic equations reviously obtained by the authors. Specific breakdown characteristics are then obtained using the effective electric field concept and experimental mean electron collision frequencies; these calculated characteristics agree excellently with experimental values. This has application for microwave cavities operating at altitudes up to 100 km     

Electrical current instability at gate breakdown in GaAs MESFET

The gate burnout (irreversible breakdown) of GaAs MESFET has been studied using two-dimensional (2-D) numerical simulation and experimental measurements of 10 ns pulsed gate-drain I-V characteristics, it is shown, that at some critical level of gate avalanche current the gate current instability appears. The instability results in formation of the negative differential conductivity (NDC) region on the S-shape gate-drain I-V characteristic, spatial instability of avalanche current and formation of high density current filaments. At some critical length of n⁺-contact regions a spatial instability results in spontaneous formation of multiple spatial-periodic filaments     

High-speed photodiode signal enhancement at avalanche breakdown voltage

It has previously been found that when photons are injected into a photodiode biased to the avalanche region, that there is a multiplication of the signal over the usual bias-voltage signal level. This multiplication is due to the created electron-hole pairs colliding with the lattice and creating more electron-hole pairs under the influence of the large biasing field. This paper presents a circuit analysis of this effect when using a high-speed silicon (Si) P-I-N photodiode and shows what the SNR bandwidth and Noise Equivalent Power (NEP) are under both normal bias conditions and avalanche bias conditions. It is shown that there is a substantial improvement in the NEP and SNR ratio at high frequencies when operating at avalanche so that the device may be made nearly shot noise limited if the multiplication factorMis sufficiently large. Microwave measurements on such a high-speed diode gave gains greater than 30 dB with a SNR improvement of 13 dB at 1.45 Gc/s. The effect was observed at frequencies as high as 2.54 Gc/s and appeared to follow a linear 1/M law with bias voltage in the avalanche region with some deviation at large values ofM. The device SNR ratio at moderately high light levels is determined by the signal-to-shot noise ratio. A high modulation depth is found to be essential to reduce shot noise. Analysis of the diode circuit reveals that the detected signal power bandwidth product is a constant. The NEP is found to vary directly with the bandwidth in a pulse type system. Avalanche operation increases the signal power by M²and decreases the NEP byMat high frequencies. The photodiode appears to nearly provide the solid-state analog of the photomultiplier tube.     

Direct-current surface breakdown of porcelain insulators in vacuum at elevated temperatures

Porcelain insulators subjected to long-term d.c. stress at temperatures in the region of 100°C have been found to suffer a deterioration in their surface vacuum breakdown strength. The letter details some preliminary investigations into this `electrolytic aging? effect, and, in particular, the effects of voltage reversal are described.     

Soft breakdown and hard breakdown in ultra-thin oxides

Soft breakdown (SBD) and hard breakdown (HBD) events are characterised separate of each other for a 3.4 nm gate oxide. It is shown that both breakdown events can have significantly different voltage and temperature acceleration behaviour. Further it is demonstrated by photoemission microscopy (PEM) for a 2.2 nm oxide that different types of breakdown paths exist. HBD-like and SBD-like breakdowns are found on the same gate area during constant voltage stress. PEM also points out that a structural change of a breakdown path can occur, usually referred to as thermal breakdown of SiO₂. It is concluded that a separate characterisation of SBD and HBD events is correct, if the stress conditions do not cause this structural change for the first SBD event.     

Improved breakdown voltage in GaAs MESFETs utilizing surface layersof GaAs grown at a low temperature by MBE

A metal-semiconductor field-effect transistor (MESFET) utilizing surface layers of GaAs grown at a low temperature by MBE (LT GaAs) under the gate electrode has been fabricated. The high trap density of LT GaAs reduces the surface fields of the FET, suppresses gate leakage, and increases the gate-drain breakdown voltage without sacrificing current drive capability. An undoped AlAs layer is incorporated between the LT GaAs layer and the channel as a barrier to the diffusion of excess As from the LT GaAs layer to the channel. A 74-μm-gate-width device demonstrated an improved breakdown voltage of 34.85 V with a g _m of 144 mS/mm and an I_dss of 248 mA/mm     

Dynamics of pulsed-microwave breakdown in a nonuniform field

A waveguide-fed mica aperture was the site of breakdown. The development of breakdown was followed both in time and space. It was found that the initial stages of breakdown proceeded as expected; the final luminosity distribution, however, seems to suggest that the initial plasma configuration results in a drastic change in the Efield distribution across the aperture.     

Nanosecond breakdown time lags in a dielectric liquid

Measurement has been made of breakdown time lags in n hexane at high stresses, and values of the order of 5ns have been obtained. The results support an earlier hypothesis that the formative time lag is normally distributed, in contrast with the recent findings of Rudenko and Tsvetkov.     

A basic limitation in interpreting field waveforms of lightningreturn strokes at a distant point

A calculation is made for the exact and dipole approximated fields of a return stroke model of a lightning discharge. It is shown that at ranges greater than 50 km, the waveform is determined by the dipole moment of the source. Thus, only limited confirmation of proposed discharge models is possible at such ranges     

Lifetime modeling of intrinsic gate oxide breakdown at high temperature

High resolution time-dependent dielectric breakdown tests are carried out on 7.2 nm gate oxide capacitors (n-type) in the electric field range 8.3–13.2 MV/cm at high temperatures (160–240 °C). It is proven that even at these high temperatures log(t_BD) is proportional to 1/E_OX and the time-to-breakdown mechanism matches the anode hole injection (AHI) model (1/E_OX model). In addition it is presented that the TDDB activation energy E_a for this type of gate oxide has linear dependence on stress electric oxide field.     

Gas discharges at low temperatures: deductions from breakdown characteristics of hydrogen at subatmospheric pressure

Measurements have been made of the breakdown voltage of a gas discharge in hydrogen with niobium electrodes for pressure and temperature ranges of 103?105 Nm?2 and 25?300 K, respectively. It is deduced that temperature has little influence on the values of Townsend's primary- and secondary-ionisation coefficients.