Radiation Effects on Distortion Characteristics of Power GaAs MESFET Amplifiers

A nonlinear MESFET model that explains the degradation in power GaAs MESFET amplifier third order intermodulation distortion (IM3) characteristics following neutron irradiation is presented. The model verifies the experimental data and shows that the significant increase in IM3 observed at a neutron fluence of 1.4 × 1015 n/cm2 and higher is mainly due to the non-linearity in device transconductance gm and output conductance go. The model also indicates that IM3 is dominated by the device gm or go non-linearity depending on applied gate bias.