Simulation Study on Thermal Damage of GaAs pHEMT LNA Under L-Band High-Power Microwave Injection

This study investigates the damage mechanisms of pseudomorphic high electron mobility transistor (pHEMT) low-noise amplifiers (LNA) under L-band high-power microwave (HPM) injection. A comprehensive model is constructed, which employs a method combining circuit level analysis and semiconductor device numerical simulation. The traditional multi-physics field algorithm was improved under the conditions of both high voltage and high electric field strength. Thereby, the nonlinear behavior, thermal failure process, and internal physical mechanisms of pHEMT devices during the injection of HPM pulses into the gate are explored. It is found that when the injection power exceeds the critical threshold, avalanche breakdown and Joule heating will trigger thermal runaway, and then a hot spot is formed under the gate on the source side. The evolution processes of carrier concentration, electric field intensity, and ionization rate are analyzed in detail to clarify the intrinsic failure dynamics of the device. Experiments conducted through a customized HPM injection platform verify the simulation results, confirming that the gain and S-parameters of the damaged LNA undergo irreversible degradation. The research results highlight the vulnerability of pHEMT based LNA to transient electromagnetic threats and provide theoretical guidance for the failure prediction and protection design of high reliability radio frequency systems.