Experimental Evaluation of Time-Dependent Dielectric Breakdown for GaN MIS HEMTs under Various Substrate Biases

Time-dependent dielectric breakdown (TDDB) under constant voltage stress (CVS) of GaN power device subjected to positive and negative substrate biases are evaluated experimentally. Under different substrate biases, the breakdown mechanisms determine the shape β of Weibull distributions and buffer traps affect the scale factor η of mean time to failure. The progressive breakdown, relating to the percolation path establishment, has been examined also. The relationship between electron trapping and de-trapping processes in the dielectric layer and GaN buffer traps revealed by the substrate bias effect are investigated.