Power GaN HEMT degradation: from time-dependent breakdown to hot-electron effects

This paper describes our most advanced results in the field of GaN-HEMT degradation, with focus on power devices. We discuss three main aspects: (i) the first part of the paper analyzes the dependence of breakdown voltage on substrate and buffer properties, by reporting the results obtained on wafers with different substrate resistivities and superlattice thickness. (ii) the second part of the paper demonstrates the existence of time-dependent breakdown of GaN buffer submitted to high vertical stress, and describes the related process. (iii) in the third part of the paper, we focus on the role of hot-electrons in limiting the dynamic performance of the devices. We demonstrate that the exposure to hard switching transitions may lead to an increase in dynamic Ron. This effect is ascribed to the presence of hot electrons, which was verified by means of electroluminescence measurements.