S. N. Tsyranov

Ultrafast current switching using the tunneling-assisted impact ionization front in a silicon semiconductor closing switch

Ultrafast current switching in semiconductors, based on the mechanism of tunneling-assisted impact ionization front, has been experimentally implemented and theoretically studied. A voltage pulse with an amplitude of 220 kV and a front duration of 1 ns was applied to a semiconductor device containing 20 serially connected silicon diode structures. After switching, 150-to 160-kV pulses with a power of 500 MW, a pulse duration of 1.4 ns, and a front duration of 200–250 ps were obtained in a 50-Ω transmission line. The maximum current and voltage buildup rates amounted to 10 kA/ns and 500 kV/ns, respectively, at a switched current density of 13 kA/cm2. The results of numerical simulation are presented, which show that the current switching is initiated at a threshold field strength of about 1 MV/cm in the vicinity of the p-n junction, where the tunneling-assisted impact ionization begins.

Solid-State SOS-Based Generator Providing a Peak Power of 4 GW

This paper describes a high-current nanosecond generator providing peak power of up to 4 GW, output voltage of 0.4-1 MV, pulse length of 8-10 ns, and pulse repetition rate of 300 Hz in the continuous mode and up to 1 kHz in the burst mode of operation. The average output power is up to 30 kW at a pulse repetition rate of 1 kHz. The generator is outfitted with an all-solid-state system of energy switching. The output pulse is formed by semiconductor opening switch diodes. The electric circuit and the design of the generator have been described. Experimental results have been given. A device for the elimination of prepulses across the load has been proposed. Testing results and numerical modeling of the device have been reported

Operation of a semiconductor opening switch at ultrahigh current densities

The operation of a semiconductor opening switch (SOS diode) at cutoff current densities of tens of kA/cm2 is studied. In experiments, the maximum reverse current density reached 43 kA/cm2 for ∼40 ns. Experimental data on SOS diodes with a p+-p-n-n+ structure and a p-n junction depth from 145 to 180 μm are presented. The dynamics of electron-hole plasma in the diode at pumping and current cutoff stages is studied by numerical simulation methods. It is shown that current cutoff is associated with the formation of an electric field region in a thin (∼45 μm) layer of the structure’s heavily doped p-region, in which the acceptor concentration exceeds 1016 cm−3, and the current cutoff process depends weakly on the p-n junction depth.

On the picosecond switching of a high-density current (60 kA/cm2) via a Si closing switch based on a superfast ionization front

A silicon closing switch with successive breakdown mode of diode structures based on a superfast ionization front is studied. In a coaxial line with a 48-Ω wave impedance, pulses with an amplitude above 100 kV and a rise time of 40 ps at an amplitude level of 0.3–0.9 are obtained. The maximum output-voltage rise rate is 2 MV/ns at a switching-current peak density of 60 kA/cm2. Numerical simulation shows that the switching time of individual structures of the device is 7–15 ps at a reverse-voltage rise rate of >100 kV/ns per structure under experimental conditions. The electric field in the p-n junction reaches the Zener breakdown threshold (∼106 V/cm) even in the case where the diode structure contains process-induced deep-level centers with concentrations of up to 1013 cm−3.

High-Power Ultrafast Current Switching by a Silicon Sharpener Operating at an Electric Field Close to the Threshold of the Zener Breakdown

A new principle of high-power ultrafast current switching by Si sharpener based on a successive breakdown of the series-connected structures has been experimentally implemented and theoretically studied. A voltage pulse with an amplitude of 180 kV and a rise time of 400 ps was applied to a semiconductor device containing 44 series-connected diode structures located in a 50- transmission line. Due to a sharp nonuniformity of the applied voltage distribution across the length of the device, the structures operate in the successive breakdown mode. Each successive structure breaks down with a shorter time interval as the electromagnetic shockwave builds. In the experiments in a 50- transmission line, we have obtained 150-kV output pulses having a 100-ps rise time. The maximum current and voltage rise rates amount to 30 kA/ns and 1.5 MV/ns, respectively. In the numerical simulations, the ionization rate of the process-induced deep-level centers, as well as the band-to-band tunneling, is taken into account. The calculations show that, at a reverse voltage rise rate across the structure of over 10^13  V/s, the electric fields that are close to the threshold of the Zener breakdown can be achieved even if the structure contains deep-level centers with a concentration of 1011 to 1012 cm-3.

A thyristor switch with a subnanosecond switching time

The possibility of triggering thyristors by an overvoltage pulse with a short rise time was investigated. Low-frequency thyristors of pellet design with diameters of semiconductor structures of 32 and 40 mm and an operating voltage of 2 kV were used in the experiments. An external overvoltage pulse that increased from 2 to 5–8 kV within a time of 0.8–1 ns was applied to the thyristors. Under such conditions, the time of switching a thyristor into a conducting state was no longer than 200 ps. An assembly of six thyristors connected in series switched a capacitor with a capacitance of 2 μF, which was charged to a voltage of 13 kV, to a resistive load of 0.25 Ω. The following results were obtained: a discharge-current amplitude of 27 kA, an initial current-rise rate of 110 kA/μs, a FWHM pulse duration of 1 μs, and a peak power in the load of 190 MW. The circuit diagram of the experiment and the obtained results are described.

The effect of a space charge on the operation of a high-power semiconductor current interrupter

A theoretical model has been developed that describes operation of a high-power semiconductor current interrupter (SOS diode) with allowance for the space charge formation. According to this model, as well as to the models based on the quasineutral approximation, the process of current breakage in a semiconductor structure of the SOS diode is related to the formation of strong field regions in highly doped parts of the structure. The space charge decreases the role of avalanche multiplication, thus providing for higher switching characteristics of the diode.

High-frequency pulse generators based on SOS diodes with subnanosecond current cutoff time

Compact high-voltage generators with a pulse power of 100–500 MW, an output voltage of 150–400 kV, a pulse duration of 3–6 ns, and pulse repetition rates of 300–400 Hz and up to 5 kHz in a steady-state and a 30-s-long burst mode, respectively, are described. The output power-amplification unit is based on an inductive storage and SOS diodes with subnanosecond current cutoff time. Physical processes in the semiconductor structure of a SOS diode operating in the subnanosecond current cutoff mode are considered. The generator circuit designs and their test results are presented.

Solid-State IGBT/SOS-Based Generator with 100-kHz Pulse Repetition Frequency

IGBT/SOS-based solid-state generator with 100-kHz pulse repetition frequency in burst mode of operation has been developed and experimentally studied. Ultra-fast IGBT transistors switch the primary capacitive store, and energy is transferred to the pumping capacitor via the pulsed transformer in about 1.5 μs. Current of this process passes via the SOS and insures its forward pumping. After the pulsed transformer ferrite core saturation the reverse current reaches its maximum value of 200–300 A in about 200 ns. At this instant the SOS cuts off the current in about 5 ns that leads to output pulse formation across external load.

Investigation of the process of voltage distribution over elements of a high-power semiconductor current interrupter

The process of voltage distribution over serially connected elements of a high-power semiconductor current interrupter in the stage of current breakage is studied within the framework of a previously developed physicomathematical model. It is established that a mechanism is operative that provides for the voltage drop leveling between unit structures of the p+-p-n-n+ type with various depths Xp of the p-n junctions. The mechanism is related to the fact that the formation of a strong field region on the stage of current breakage in the unit structures with larger Xp begins later, but the expansion of this region proceeds faster than the same processes in the units with smaller Xp.