| Summary: | Silicon carbide junction field-effect transistors (SiC JFETs) are promising candidates as devices applicable to radiation conditions, such as the decommissioning of nuclear facilities or the space environment. We investigate the origin of the threshold volage (<i>V</i><sub>th</sub>) shift and hysteresis of differently structured SiC JFETs. A large positive <i>V</i><sub>th</sub> shift and hysteresis are observed for a depletion-type JFET with a larger depletion layer width. With changing the sweep range of the gate voltage and depletion width, the <i>V</i><sub>th</sub> shift was positively proportional to the difference between the channel depth and depletion width (channel depth–gate depletion width). By illuminating the sub-band gap light, the <i>V</i><sub>th</sub> of the irradiated depletion JFETs recovers close to nonirradiated ones, while a smaller shift and hysteresis are observed for the enhancement type with a narrower width. It can be interpreted that positive charges generated in a gate depletion layer cause a positive <i>V</i><sub>th</sub> shift. When they are swept out from the depletion layer and trapped in the channel, this gives rise to a further <i>V</i><sub>th</sub> shift and hysteresis in gamma-irradiated SiC JFETs.
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