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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.

AlGaN/GaN devices for both power and RF applications have been investigated in this work. In particular, regarding power applications, 100 V p-GaN gate transistors have been analysed both in DC and in dynamic conditions with specific attention to the high temperature behaviour.As a first step, the high temperature behaviour of the on-resistance (RON) of a reference process (STD process) has been investigated. The role of the different resistive components of the transistor has been analysed by evaluating how their relative weight changes with the temperature increase. Then, two different p-GaN process variations (process A and process B) have been proposed and compared to the STD process to show their improvement in terms of a limited RON increase at 150 °C, highlighting the relevance of an improved p-GaN gate processing.Secondly, the temperature effect on the RON-degradation induced by off-state drain voltage stress has been investigated in process B-like devices. The impact of temperature on the time required to reach a steady state degradation has been addressed, enabling the comparison of the RON degradation (RON/ RON0) at equilibrium. Tests performed on several samples have demonstrated the invariance of the RON/ RON0 ratio in the 25 °C to 150 °C range, suggesting the possibility to reduce the measurements required for dynamic-RON evaluation at different T.Finally, RF devices (featuring Schottky metal gate) have been characterized in terms of DC/RF performances and long-term reliability (through HTRB tests). Different trials with increasing aluminium content of the AlGaN barrier have been compared, showing the correlation with the maximum saturation current and the output power. Moreover, the trade-off with reliability specifications has been put in evidence.

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.