VTH & Gm, max Instability Analysis of the Multiple GaN Chips based Cascode Power Module

In this work, we present developed and tested a multiple-GaN-chips based cascode power module to scale up the power ratings. This cascode power module consists of two switching elements that connect multi-GaN-chips of AlGaN/GaN-on-Si HEMT cells with low voltage Si MOSFETs in series. As an electrical characterizations, static output and transfer characteristics of the module were tested at room temperature and with reverse-leakage characteristics, the constructed cascode power module has a blocking voltage of more than 550 V. Following electrical characteristics, we present an extensive study of threshold voltage (VTH) and transconductance instability (Gm, max) of the cascode power module under positive and negative gate bias temperature instability experiments. The trapping and de-trapping of electrons from pre-existing oxide traps lead the power module to negative and positive VTH instabilities and Gm, max degradations. These findings on performance and instability open the path for a better understanding of enhancements and failure causes, which will help to accelerate the growth of emerging GaN cascode technologies.