Gamma-Induced Leakage in Junction Field-Effect Transistors

Junction field-effect transistors are normally considered to be "hard" to gamma and neutron effects. However, for several types of devices measured, we observed an increase in the gate-to-body leakage current which is significant in low-power circuits. Data is presented for two device structures irradiated at three different dose rates; 1E9 rad(Si)/s, 5.5E2 rad(Si)/s and 0.9 rad(Si)/s. Parameter measurements on the devices before and after exposure to radiation indicate that the leakage results from a surface inversion under the interdigitated source and drain metallization. This hypothesis is supported by the time-dependent decay in leakage current after radiation and by the lower leakage levels observed on devices that have a highly doped "guard band" around the channel diffusion.