Reliability Assessment of 60-GHz GaN Power Amplifier Under High-Level Input RF Stress

This article investigates the degradation mechanism of a 60-GHz third-stage gallium nitride (GaN)-based monolithic-microwave integrated circuit (MMIC) power amplifier (PA) under RF stress at different input power levels. The same experiments were performed on the discrete device with a size identical to the power stage of the MMIC PA. The experimental results at the device level did not exhibit any shift in the threshold voltage (
${V}_{\text {th}}$
) after the RF stress. Meanwhile, the simulated dynamic load lines indicate that the voltage swings exceed the critical voltage (
${V}_{\text {crit}}$
) under high-level RF stress conditions. It is thus concluded that the inverse piezoelectric effect is the main factor for the performance degradation. Generation of the defects and dislocations in the crystal is expected at the drain side due to the high electric field in the channel. Based on the experimental results, we have identified the early saturation of the second stage as the major reason for the overall degradation at the MMIC level.