Characteristics of GaAs DCFL MESFET´s and inverters exposed to high-energy neutrons

A systematic investigation of the effects of high-energy neutrons on GaAs metal-semiconductor field-effect transistors (MESFETs) and direct-coupled FET logic (DCFL) gates has been carried out. Measurements were made of the threshold voltage shifts and the transconductance and saturation current degradation of GaAs enhancement- and depletion-mode MESFETs, which comprise the DCFL logic gates, at neutron fluences ranging from 5×10¹³-2×10₁₅ n/cm² (E>keV). DCFL inverter characteristics were measured and successfully simulated with SPICE using device parameters extracted from the neutron-damaged FETs. Ring oscillator measurements were made to determine the effects of high-energy neutrons on the frequency performance of DCFL circuits. Measurements confirm that propagation delays scale inversely with the device transconductance. The results of this investigation are useful in predicting how GaAs ICs, fabricated using DCFL logic, will perform in a high-energy-neutron environment