S. V. Korotkov

Novel Closing Switches Based on Propagation of Fast Ionization Fronts in Semiconductors

New concept of triggering the fast ionization fronts in semiconductors with the field-enhanced ionization of deep electron traps is described. Closing switches designed on the base of this concept has been called the Deep Levels Dinistors, DLDs. These devises are able to form high current pulses with subnanosecond risetime and low voltage drop after switching. As an instance three generators based on DLDs are described. The possibility of picosecond switching on the base of tunnel assisted impact ionization front is discussed.

Switching Possibilities of Reverse Switched-on Dynistors and Principles of RSD Circuitry (Review)

The results of studies of reverse switched-on dynistors (RSDs) intended for use in high-power pulse and converting devices are generalized. The basic principles of designing high-power RSD switches are analyzed. The main circuit designs of pulse and high-frequency RSD-based devices are described. The results of tests of high-voltage microsecond and submicrosecond pulse RSD generators with a pulse power of 108–1010 W and high-frequency RSD inverters with a mean power of 104–105 W are presented.

Dynistors with nanosecond response times

The results of studies of deep-level dynistors (DLDs) in modes of switching high-power nanosecond current pulses at a current rise rate of up to 200 A/ns unique for semiconductor switches are presented. The dependences of the switching energy loss in DLDs on the amplitude of the control current and the shape of triggering voltage pulses are shown. The electrophysical processes developing at the edge surface of a DLD subjected to the application of high-voltage triggering pulses are analyzed.

Sub-nanosecond semiconductor opening switches based on 4H–SiC p+pon+-diodes

Abstract 4H–SiC p + n o n + - and p + p o n + -type diodes have been fabricated and evaluated as opening switch devices which are known in Si to employ the effect of fast reverse current break after switching the diodes from forward to reverse bias conditions. The recovery properties of p + p o n + -diodes were found to be drastically differ from those of p + n o n + -type ones. In p + n o n + -diodes, recombination processes predetermine soft recovery behavior in a time of approximately 16 ns. In p + p o n + -type diodes, purely drift mechanism was found to be responsible, under proper conditions, for the very fast reverse current break in a time less than 1 ns. p + p o n + -Diodes were utilized in a pulse generator which was fabricated with an inductive energy storing unit. The rise time of 400-V pulses generated, about 4 ns, was found to be equal to the quarter of the oscillation period of the LC-tank consisting of 2-μH storing inductance and 2-pF 4H–SiC diode capacitance.

A 0.5-MJ 18-kV Module of Capacitive Energy Storage

A module of the capacitive energy storage is designed for experiments with high-current electrical discharges in dense media. The module is remotely controlled and consists essentially of eight capacitor cells with semiconductor switches built around reverse-switching dynistors (RSDs). It includes a charger with a high-frequency inverter, a protective contactor with normally closed high-voltage contacts, cell RSD switch controls, and control and diagnostic equipment provided with a programmable logic controller. The semiconductor switches in the capacitor cells are triggered by light pulses transmitted from a remote-control panel over eight fiber-optic cables. Information exchange between the module control and diagnostic system and the remote terminal is realized likewise over two fiber-optic cables. The storage is designed to operate in a programmable discharge mode in which the semiconductor switches in the capacitor cells are activated by a preset time-sequence program. The maximum current pulse amplitude of 400 kA at the module output is reached under synchronous discharge of all eight cells in the short-circuit mode. In these conditions, the pulse rise time is 150 μs. The volume of the capacitor module is 1.3 m3 .

A high-power semiconductor switch of high-voltage pulses with a rise time of nanosecond duration

The results of studies of new fast-acting semiconductor devices—deep-level dynistors intended for use in high-power devices of nano-and microsecond pulsed-power technology—are presented. The possibility of switching multikiloampere current pulses having a rise rate of 200 kA/μs with the use of a single device with a 12-mm-diameter structure is shown. A high-power switch based on an assembly of dynistors with an operating voltage of 12 kV connected in series is described. The switch is capable of switching current pulses with a 1200-A amplitude and a 4-ns rise time.

High power semiconductor-based nano and subnanosecond, pulse generator with a low delay time

One of the promising designs of high-power nanosecond and subnanosecond pulse generators is based on the fast ionization dynistor (FID) stack triggered with nanosecond pulse of overvoltage. This pulse is usually formed by semiconductor opening switches. Delay time of these switches equals the sum of forward and reverse current pulse duration, i.e., several hundreds of nanoseconds. The novel opening switch, inverse recovery diode (IRD), is capable of forming a nanosecond pulse of voltage with the delay time equal to the reverse current pulse duration (15-20 ns) due to the special diode structure. High-voltage nanosecond pulse formed with IRD is used for fast triggering of the first FID from high-voltage dc-biased FID stack. The resulting fast overvoltage pulse is applied to the second FID, etc. As a result, the high-voltage FID-stack is switched for units of nanosecond. Total delay time of IRD-FID-based pulse generators is less than 30 ns.

Pulse Power Nanosecond-Range DSRD-Based Generators for Electric Discharge Technologies

New design of power nanosecond-range generators for electric discharge in gases is described. These generators are based on semiconductor opening switches-Drift Step Recovery Diodes (DSRD). The main advantages of DSRD are very short switching-off time (<;3 ns), high commutated power (>500 kW for single DSRD with 2 cm2 of semiconductor structure), and high reliability of high voltage stacks consisting of many connected in series DSRD. The experimental results of DSRDbased generator application for ozone production and waste gas cleaning are presented. The main parameters of the generators: output pulse voltage up to 36 kV, pulse rise time <;4 ns, pulse repetition rate up to 3.5 kHz, output pulse power >4.5 MW.

Reverse switch-on dynistor switches of gigawatt-power microsecond pulses

A high-power (150 kA and 16 kV) small switch based on an assembly of reverse switch-on dynistors (RSDs) connected in series and a coaxial saturable-core choke, which creates conditions for their efficient switching, is described. An essential feature of this switch is a drastic reduction of the duration of the control action, as a result of which minimum dimensions and a low inductance of the saturable-core choke are ensured at a high (25 kA/μs) rise rate of the switched current. Increases in the control-current amplitude and rise rate that are required for maintaining the triggering charge at a constant level are attained thanks to the use of a fast-acting switch based on new semiconductor devices—deep-level dynistors—in the RSD-control circuit.

Installation for air cleaning from organic impurities by plasma formed by barrier discharge of nanosecond duration

A prototype installation for air cleaning by plasma, which consists of a barrier-type discharge reactor and a high-voltage nanosecond-pulse supply generator, which is based on drift step recovery diodes, is considered. A stable corona-type barrier discharge was obtained at a 3-kHz supply-pulse repetition frequency. The discharge remained nonlocalized even at a small gas-discharge gap (∼6 mm) due to a short (∼25 ns) pulse duration, which allows a quite uniform effect on the air flow. The high rise rate (∼6 kV/ns) of the applied supply voltage pulses determines the high voltage amplitude (∼25 kV) at the reactor at the breakdown moment and allows maintenance of high electric-field intensity and a high intensity of plasma chemical processes. Thus, an electrical power lower than 8 W is required at the reactor input to produce 1 g of ozone per hour. The concentration of methylmercaptan in air during waste-water smell deodorizing at State Unitary Enterprise “Vodokanal of St. Petersburg” was reduced down to an allowable level of 0.5 mg/m3 at the electrical power consumption no higher than 0.25 W per cubic meter of air.