Imprcved Fast Neutron Tolerance of GaAs JFET's Operating in the Hot Electron Range

The fast neutron induced degradation of the electrical characteristics of n-channel GaAs junction field effect transistors (JFET's) operating in the Shockley mode (thermal equilibrium) was estimated previously. Advances in technology have led to the fabrication of devices with micron sized channel lengths which are capable of response at microwave frequencies. Short channel lengths, however, result in device operation under thermal nonequilibrium conditions and hot electron effects must be considered. The theory of Lehovec and Zuleeg, which provides the characteristics for JFET's operating in the hot electron range, is employed in this paper to estimate the neutron degradation of these devices. It is shown that JFET's operating in the hot electron range are more resistant to neutron exposure than are JFET's operating in the Shockley region. Devices with channel doping concentration of 1017 cm-3 are predicted to survive fluences of 1016 neutrons/cm2. Some preliminary test results are reported.