Home – Home – Jornals – Chemistry for Sustainable Development 2001 number 7

Semiconductor power devices are employed widely in pulsed power applications. A first goal of device development for the applications is to establish high di/dt characteristics similar to that of spark gap switches, namely, 10¹²A/s. We examined turn-on characteristics of SI-thyristors for fast high-voltage pulse generators. The SI-thyristors have a buried gate structure in which the gate electrodes are placed in n-base region. Since they are normally on-state, gate electrodes must be negatively biased to hold off-state. The SI-thyristors at on-state behave similar to pin diodes. We characterized three kinds of SI-thyristors, two of which were for power electronics use with a rated voltage of 4000 V. The device named RT201 was designed for pulsed power applications. The difference among them is device structures at the vicinity of anode. The punch-through and anode shorted structures are commonly used to improve turn-off characteristics for power electronics. The RT201 device with a rated voltage of 5500 V has the punch-through structure and is not an anode-shorted device. The turn-on speed is mainly determined by carrier injection rate to the n-base region. Therefore performance of the gate driving circuit influences fast turn-on characteristics. When the newly developed high current gate driver was used, the fastest turn-on operation with Tf = 35 ns and di/dt = 9.5*10¹⁰A/s was obtained in the RT201 device. We made a stacked SI-thyristor switching unit to characterize repetitive and higher voltage operation. The stacked unit comprised three SI-thyristors, and each of them had the gate driver. The switching unit was successfully operated with the repetition rate of 2 kHz at 10 kV.