The ionizing radiation dose rate response of GaAs junction field‐effect transistors (JFETs) cannot be explained by the usual photocurrent model. A model is proposed in which superhot electrons from a region of many tens of microns are collected ballistically over the repulsive built‐inP+gate barrier of irradiatedn‐JFETs providing a gate current of polarity opposite to that of the ordinary junction photocurrent. Steady state is established by inflow of thermal electrons from the source which increases the bulk electron concentration and causes a drift velocity saturated drain current through the substrate at positive drain voltages. Since collection range of holes is much shorter than of electrons,p‐JFETs do not exhibit this effect.