1. Investigation of the effect of nanosecond cutoff of superdense currents in semiconductor diodes (SOS effect).

The principal difference between the SOS effect and other methods of current switching in semiconductor diode structures has been established, which consists in the fact that the development of the current cutoff process does not occur in the low-doped base of the structure, as is the case with other devices, but in the high-doped p-region. In this case, the base of the structure and the p–n junction are filled with a dense excess plasma with a concentration of the order of 10¹⁶ cm^-3 and do not participate in the current cutoff process. The speed of the SOS process is determined by the fact that at the current cutoff stage an electric field with a value of more than 200 kV/cm is arisen in a narrow (about 40–50 μm) layer of the p-region. The time of formation of such a layer at the velocity of the plasma front of units of μm/ns is ~10^-8 s.

It is shown that for structures operating in the SOS-effect mode, an increase in the depth of the p–n junction leads to a decrease in the time of current cutoff and an increase in the overvoltage factor. The dependence is due to an increase in the velocity of the concentration front of the excess plasma moving along the p-region at the stage of reverse pumping, which increases the width of the strong-field region (increase in the voltage across the structure) and reduces the time of its formation (decrease in the current cutoff time).

The mechanism of operation of a semiconductor opening switch at ultrahigh current densities has been investigated. It is established that the nanosecond current cutoff process (SOS effect) is realized up to the ultimate current density of 100–115 kA/cm², when during the reverse current pulse, the overheating and thermal breakdown of the semiconductor structure occurs.

The effect of subnanosecond cutoff of superdense currents in high-power SOS diodes has been discovered and investigated. The effect is observed when the forward pumping duration is lower than 60 ns, reverse pumping duration is lower than 20 ns, and when a cutoff current density is over 3 kA/cm². The depth of the p–n junction in the structure should exceed 180 μm. The process is characterized by the appearance of two independent regions of the strong field in the p-region of the structure, which at the current cutoff stage expand with a velocity close to the saturation velocity of the carriers, and overlap each other in a time of hundreds of picoseconds.

The effect of generation of powerful microwave voltage oscillations across a silicon no-base diode has been detected and investigated when a high-density reverse current passes through the diode. Voltage oscillations with amplitude of up to 480 V, center frequency of 5 to 7 GHz and a power of 300 kW were obtained. It has been established by theoretical methods that generation of the oscillation is caused by the instability of the distributions of holes and electrons concentration, and electric field in the vicinity of the p–n junction existing when the reverse current with a density of 3 to 20 kA/cm² passes through the diode. It is shown that the maximum power of oscillations can reach 1 MW at a frequency of ~10 GHz at the current density of ~15 kA/cm².

Main publications: 2–4, 7, 10, 13, 16–17, 22–23.