The GaN HEMT power device emerges as a promising wide-bandgap component for obtaining ultra-compact and very high efficiency power converters. Nevertheless, its long-time switching operation capability in high overload regimes near or just above its maximum ratings remains unknown. The physical degradation mechanisms specific to GaN HEMT as well as the associated electrical signatures must now be established and better understood. In this article a stress protocol is proposed combining or not functional drain-source over-voltage switching and transient low dead-time cross-conduction stresses. A no-loaded Half Bridge (HB) is used. All stress parameters studied have been associated to electric changes such as drain-source, gate-source leakage currents, and threshold voltage drifts of intrinsic values and even some physical degradation by LIT compound analysis. After analysis, it appears that both the electric field and the current are very stressful for the devices and lead to current leakage caused by physical degradation. The aging observed might be generated from the injection of hot electrons and located depending upon the drain voltage value which influences the depletion region and thus the electric field peak.