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In this paper, a new method for evaluating hot-electron degradation in p-GaN gate AlGaN/GaN power HEMTs is proposed. The method exploits a commercial parameter analyzer to study VTH and RON drifts induced by on-state stress at VDS = 50 V. The results show that VTH drift and part of the RON degradation induced by the on-state stress are recoverable and likely due to the ionization of C-related acceptors in the buffer. This was confirmed by a preliminary characterization of C-related buffer traps. Conversely, the remaining part of RON degradation (not recovered in 1000 s) was strongly affected by the surface treatment. The current level set during on-state stress affected the amount of non-recoverable degradation, confirming the involvement of hot electrons. Thanks to the monitoring of the parameters’ recovery, the proposed method provides important insights into the physical mechanisms governing the parameters’ degradation. This extends the capabilities of state-of-the art systems, without the need for custom setup development.

The role of the magnesium (Mg) doping and its electrical activation on the off-state of p-GaN/AlGaN/GaN HEMTs has been investigated in this work. Firstly, the effect of different Mg doping profiles has been studied via the help of Technology Computer-Aided Design (TCAD) simulations, with the objective of analyzing the band diagrams of the structure. Then, it has been shown how experimental Capacitance–Voltage measurements can be useful to obtain information on the net acceptor concentration in the p-GaN. As a result, devices with an undoped (magnesium-free) GaN gate have been experimentally compared to devices whose p-GaN gate has been activated via a reference annealing process. Finally, results on a device characterized by an improved p-GaN activation have been presented and compared, showing improvements on several parameters of both off- and on-state, thus underlining the key role of the Mg activation process in the overall performances of normally-off GaN HEMTs.