Burnout of Junction Field Effect Transistors

This paper presents the results of a study on burnout characteristics of n-channel silicon junction field effect transistors as established by electrical pulse injection tests and high dose rate radiation tests. For reverse biased pulse injection tests on JFETs connected in a diode configuration (source and drain tied together), current-mode second breakdown was observed at short failure times (tf<0.1¿s) while thermally-induced second breakdown occurred at longer times. The high voltage JFETs tested were found to be much more susceptible to reverse bias pulse injection damage than were the low voltage JFETs (attributed to surface effects). When the gate lead of an actively biased device was driven with a forward biased pulse, the JFET failed due to heating in the pinchoff region of the channel causing a drain-gate short. Under Flash X-ray radiation tests, the diode configuration exhibited photocurrent enhancement near the same current levels at which current-mode second breakdown occurred in the pulse injection tests, but higher power dissipation could be tolerated before device damage was incurred. When irradiated in the active configuration, the onset of photocurrent enhancement resulted in a sustained high current mode which persisted until metallization burnout occurred.