Thermal Analysis on the Degradation of GaN HEMTs

High temperature operation(HTO) experiments were performed on industrial GaN HEMTs devices. Several degradation failure modes of DC parameters such as transconductance reduction, threshold voltage shift, and gate leakage current increase were identified. The vertical failure localization and analysis of the devices were carried out by electrical method. The results show that the increase of the degradation of the die attach layer is the main reason for the increase of the junction temperature and thermal resistance of the devices. Furthermore, the results are analyzed by three-dimensional X-ray imaging confirming the degradation of the die attach layer. The voids in the die attach layer expanded during the high temperature operation stress experiments, led to a worse heat dissipation performance, which resulting in increased junction temperature, and further accelerate the performance degradation of the devices.