Investigation of TID-induced capacitance variation in GaAs edge-lift capacitors and its effect on RF impedance matching

This paper investigates the total ionizing dose response of passive components fabricated in a commercial GaAs process, with a focus on dose-dependent capacitance variation in fringe-field–dominant structures. Measurements indicate that the edge-lift capacitor exhibits the highest total ionizing dose(TID) sensitivity, with its effective capacitance increasing from 7.65 pF to 22.96 pF after 300 krad(Si) irradiation at 10 GHz. This behavior is consistently reproduced in electromagnetic simulations by increasing the relative permittivity of the SiN dielectric from its nominal value of 6.9 to 8.5, enabling a radiation-equivalent dielectric modeling approach. When applied to an RF amplifier matching network, the TID-induced capacitance variation shifts the input impedance from 43.75 + j27.15 Ω to 33.8 + j5.35 Ω, accompanied by degradation in gain and noise performance. These results demonstrate that TID-induced dielectric property changes in GaAs passive components can be effectively captured using radiation-equivalent electromagnetic modeling and can significantly impact RF circuit performance.