High Energy Gamma Radiation Effects on Commercially Available Silicon Carbide Power JFET Transistors

Abstract

An investigation of high power commercially available semiconductors made with compounds such as, silicon carbide (SiC), are being investigated for space applications and other harsh environments. The research involves observing the electrical characteristics of two types of 4H-SiC vertical depletion-mode trench junction field effect transistors (JFETs) before and after irradiation from a 60Co gamma ray source. The normally-on trench vertical JFETs have a nominal blocking voltage of 1200V and a forward current rating 52A, while the normally-off trench vertical JFETs have a nominal blocking voltage of 1200V and a forward current rating 17A prior to radiation. The on-state and blocking I-V characteristics were measured before the devices were irradiated, then measured again afterwards for comparison.

During irradiation and annealing, the JFETs were biased with a positive gate voltage of 3V with source, drain, and substrate tied to ground. The test batch was irradiated using the Co-60 source at the Auburn University Leach Science Center. Samples were irradiated at a dose rate of 69.9 rad(Si) for a total accumulated dose of 7Mrad. The evaluated SiC devices performed well following extremely large gamma ray exposures. In this paper, it is demonstrated that the evaluated SiC transistors have the potential to operate satisfactorily in high gamma radiation environments, including commercial and high altitude/space applications. No significant degradation in the device characteristics was observed after a total ionizing dose of 7 Mrads.