In-Circuit Assessment of the Long-Term Reliability of E-Mode GaN HEMTs

This article presents an in-circuit approach to assess the long-term reliability of enhancement-mode GaN HEMTs. A synchronous buck converter conceived for the on-board transistors' characterization is proposed. Here, high-side and low-side power transistors operate under realistic stress conditions, whereas their degradation is assessed by measuring, in-circuit, the full I-V characteristics at prefixed stress times. Moreover, a long-term reliability analysis of commercial 80-V GaN HEMTs is reported. Threshold voltage and ON-state resistance degradation induced by the buck converter operation is investigated, as well as their dependencies on the input voltage, duty cycle, ambient temperature, and output current. Results highlight a clear difference compared to standard dc-stress and reveal a strong correlation between the degradation of the high-side transistor and the input voltage. On the contrary, the low-side transistor degradation is almost insensitive to the different operating regimes of the power converter.