Study of Aging Characteristics for Cascode-GaN-Field Effect Transistor (FET) Device under High Electric Field Stress

This paper investigated changes in threshold voltage, on-resistance, turn-on delay, and turn-off delay of cascode GaN FETs under high electric field stress. As a result, the threshold voltage decreased, and the on-resistance increased under the stress of applying a positive high voltage. Also, the turn-on delay was reduced, and the turn-off delay increased. On the other hand, under the stress of applying a high negative voltage, the threshold voltage, on-resistance, and turn-on delay decreased, and the turn-off delay increased. These results imply that the conduction loss of the cascode GaN FET increases, and the dead time of the voltage source converter composed of the cascode GaN FET increases under positive high voltage stress. Also, the fact that the threshold voltage decreased under both positive and negative high voltage stress means that if the cascode GaN FET is subjected to high voltage stress, the reduced threshold voltage is more likely to turn on undesirably even at low gate voltages. Copyright © The Korean Institute of Electrical Engineers.