Development of a Semiconductor Opening Switch at Soreq NRC

The semiconductor opening switch (SOS) diode, invented in Russia around three decades ago, is attractive for a variety of pulsed power applications due to its ability to interrupt currents of thousands of amperes in several nanoseconds in inductive storage generators. This allows delivering hundreds of megawatts into the load. The SOS has a p⁺-p-n-n⁺ structure, where the p-n junction depth could be ∼200 µm. Thus, the fabrication process of such structure requires a long diffusion time at a very high temperature, and was not suited for mass production in regular fabs. We present the design, simulation, fabrication, and testing of a Si SOS diode developed at Soreq NRC. It consists of a 180 µm epitaxial structure with a p-n junction depth of ∼110 µm. In a single die testing, we used a fast driving circuit. A peak negative voltage of 1515 V with a rise time of 1.56 ns was obtained on a matched 50 load. The voltage rise rate, of 0.97 kV/ns, is the highest record obtained for a single Si current interruption die. In order to test the diode at high voltages (HVs), we used two setups of SOS-based generators based on magnetic compression. We compared its original SOS diode developed in Russia with a stack of epi-SOS diodes. In the first setup, an epi-SOS made of 65 dies in series with a cross section of 25 mm² was used. The reverse current was 927 A. The peak load voltage on a 46 load was 37.4 kV with a rise time of 25 ns. In the second setup, an epi-SOS made of 130 dies in series with various cross sections of 1, 2, and 3 cm² was used. For the 3 cm² stack, a 173-kV, 7.5-ns rise time pulse was obtained on a ∼224 low-inductance resistive load.