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GaN technologies have penetrated the microelectronic markets, proving the high potential of this technology for a wide variety of applications (optoLEDs and Laser, power and RF electronics). However, robustness of these widebandgap technologies still needs to be improved: a large number of studies have addressed the main different roots provoking degradation of RF, DC or thermal performances of transistors dedicated to high frequency applications. Experiencing reliability studies mechanisms on a given technology cannot be carried out to another one, depending on changes of the doping, passivation layer thickness or material, content of Al or In in the ternary composition of the channel... Among the more problematic causes of degradation for high electron mobility transistors (HEMT), traps need to be accurately identified: this paper proposes the jointed expertise using three different experimental workbenches to identify trapping-detrapping effects and free charges effects in AlGaN/GaN HEMT devices over samples from a European foundry. Different samples have been stressed using DC biased devices at ambient temperatures of 25°C and 150°C, and using HTRB stresses at 150°C. Stressed devices and virgin samples are measured using pulsed I-V characterizations, current Deep Level Transient Spectroscopy (I-DLTS) measurements and low frequency noise (LFN) measurements. Each experimental setup has its own specificities, and allows the determination of activation energies and capture sections of the traps, or how these traps or charges affect the transistor performance under realistic HF conditions. Drain-Lag and Gate-lag signatures evidence the large stress effect on the devices, but with different nuances partially correlated to gate leakage currents. Traps measured with I-DTLS and LFN techniques evidence partially correlated origins, and thermally activated traps can be discriminated from electrically activated ones.