Failure Behavior and Mechanism of p-GaN Gate AlGaN/GaN HEMTs in the Third Quadrant Under Repetitive Surge Current Stress

In this article, the failure behavior and mechanism of p-GaN gate AlGaN/GaN high-electron-mobility transistors (HEMTs) in the third quadrant under repetitive surge current stress are investigated. Repetitive stress tests with different surge current peak values (
${I}_{\text {peak}}$
) are carried out. At high
${I}_{\text {peak}}$
, as the stress cycle increases, the evolution of the peak value of surge voltage induced by surge current shows an obvious turning phenomenon and a significant increasing trend. When the surge voltage reaches a certain value, the gate-to-source breakdown occurs, and then, the device is burned out. We propose that the degradation of the third-quadrant conduction characteristics results in the change of surge voltage, and excessive electric field intensity induced by high gate-to-drain voltage (
${V}_{\text {GD}}$
) causes the gate Schottky junction breakdown. It is confirmed by further experiments, electrical performance characterization, and simulation. Inconsistent degradation of the two-dimensional electron gas (2DEG) channel in various regions causes the aforementioned turning phenomenon. As the stress cycle increases, the channel degradation in the gate-to-source/drain access region occupies a dominant position. In this situation, the
${V}_{\text {GD}}$
increases continuously, which will enhance the tunneling effect at the Schottky junction, until breakdown occurs. Besides, the device shows better surge current reliability at higher gate-to-source voltage. These results provide important insights into the improvement of GaN HEMTs reliability.