Failure Analysis of 200V p-GaN HEMT under Unclamped Inductive Switching Conditions

Power electronic systems based on gallium nitride (GaN) devices are expected to significantly reduce the power loss and increase the operating frequency. This makes GaN devices very promising for next-generation medium-low voltage power electronics, like applications in electric vehicles, 5G communication, lasers, and fast charge. However, reliability issues are still an obstacle to the widespread application of p-GaN high electron mobility transistor (HEMT). It is of great significance to study the reliability of p-GaN HEMT which suffers unclamped inductive switching (UIS) shock. This work reveals the UIS failure mechanism of commercial 200V p-GaN HEMT. During entire UIS process, the p-GaN HEMT does not consume the energy stored by the load inductance. The energy transferred from the load inductance makes the electric field of the passivation layer under the source field plate (SFP) rise rapidly, causes the catastrophic breakdown of the passivation layer. Once the maximum drain-source voltage (V
DS, max
) exceeds the critical peak voltage (V
peak
), the UIS failure occurs. The ionized traps in passivation layer and hot carrier injection caused by high electric field lead to the formation of a penetration current path between SFP and AlGaN barrier layer. This work provides a new UIS failure mechanism of 200V p-GaN HEMT.