Operation of a semiconductor opening switch at the pumping time of a microsecond and low current density

The mechanism of operation of a semiconductor opening switch (a SOS diode) at the forward-pumping time of a microsecond and low current density was studied. The current’s cutoff time shorter than 10 ns at the voltage across the SOS diode as high as 80 kV was obtained experimentally at the reverse-pumping time ∼200 ns and the cutoff-current density of about 120 A/cm2. These are the results of numerical simulation of processes in the dynamics of the electron-hole plasma in the diode at the stages of pumping and current cutoff. It is shown that the stage of the current cutoff is similar to the conditions of the SOS effect observed at a high current density and is also related to motion of the concentration front of excess plasma along the heavily doped p-type region of the structure. In spite of the low density of current in the course of its cutoff, the switching process takes several nanoseconds. The reason is that the low current density is compensated by a low concentration of the excess plasma at the front, which retains the high velocity of motion of this front at the stage of the current cutoff.