Breakdown investigation in GaN-based MIS-HEMTdevices

Breakdown mechanisms in AlGaN/GaN HEMT devices are here analyzed, placing particular emphasis in the analysis of GaN based device grown on silicon substrate. Based on combined experimental data and bi-dimensional numerical simulation we demonstrate that many physical mechanisms can contribute to increase the leakage current leading to the final breakdown of the device. In particular we show how band-to-band phenomena, rather than impact ionization, can be responsible of the premature breakdown even in double-heterostructure HEMTs.