Study On Radiation Hardness Of 4H-SiC PiN Diodes

Due to the low-doped intrinsic layer and the high critical breakdown electric field, 4H-SiC PiN diodes have very high breakdown voltage. The thin intrinsic layer and the high electron saturation velocity also gives 4H-SiC PiN diodes better reverse recovery characteristics over the silicon counterparts. The high critical displacement energy of silicon carbide contributes to the good radiation hardness of 4H-SiC PiN diodes.Till now, there are limited reports of the dc and transient characteristics of silicon carbide switching diodes under radiative environment. This thesis presents some work on those results in concern.Numerical model has been setup with proper parameters for 4H silicon carbide. The I-V characteristics of 4H-SiC PiN diodes have been simulated with ISE-TCAD. The turn-on voltage at a current density of 100A/cm2 is 2.8 volts. Avalanche multiplication breakdown has taken place when the diode is reverse-biased to 1.4kV. The turn-off transient process has been studied too. At room temperature, when the diode is switched from forward-biased at 3 volts to a reverse bias of 50 volts, the turn-off time is only 69 nanoseconds while the peak reverse current is 8.45×10?4 ampere. The simulation results show that the transient characteristics have positive temperature coefficients.Some work has been done on the dc and reverse recovery characteristics of 4H-SiC PiN diodes after proton and electron radiation. The currents at low forward bias show slight reduction, and the turn-on voltage decreased a little after both kinds of radiation. In general, radiation has little effects on the forward characteristics of 4H-SiC PiN diodes. The reverse leakage current actually decreases. The transient characteristic shows some improvements after radiation. The diode performance is superior to before radiation even at high temperature. In conclusion,4H-SiC PiN diode is proved to be with good immunity under radiation.