Individual and parallel behavior of high current density, high-voltage 4h-silicon carbide PiN diodes

The preferred method of switching the very high currents and voltages present in electromagnetic launch systems is to use arrays of solid-state devices. The effort to reduce the overall switch mass and volume has generated interest in advanced high-power, high-temperature semiconductor materials such as silicon carbide (SiC). Devices produced from SiC are expected to provide significant performance improvements in very high-power switching devices over current devices based on silicon (Si) materials. The performance improvement expectations are based on SiC´s superior material properties, most notably for power devices are a band gap of 3.26 eV (three times that of Si), a breakdown field of 2-4 MV cm^-1 (order of magnitude better than Si), a thermal conductivity of 4.5 W cm^-1 K^-1 (three times that of Si), and a saturated drift velocity of 2×10⁷ cm s^-1 (two times that of Si). This paper describes the results of recent experiments at the Institute for Advanced Technology at The University of Texas at Austin in which SiC PiN diodes arranged in parallel pairs are subjected to high current density pulses. The failure modes of paralleled devices are compared to the failure modes seen in individual devices subjected to high current density pulses (maximum of 2.34×10⁴ A cm^-2). The results show current equalization between paralleled high-voltage diodes when subjected to high current densities, which suggests that high-voltage SiC active devices will also function well in parallel arrangements.