  The reliability of AlGaN/GaN HEMTs adopting Fe and C co-doping, with high and
low carbon doping concentration was investigated by means of different stress
tests. Firstly, DC and pulsed I-V characterization at room temperature are
discussed, then drain step stress tests at different gate voltages are
compared, afterwards, the constant stress at different bias points are
discussed. Results show that the high C HEMTs showed reduced DIBL, smaller
leakage current, as well as decreased electric field, leading to an improved
robustness during on-state stress testing, with respect to the reference ones.
Failure modes during constant voltage stress consists in a decrease of drain
current and transconductance, accelerated by temperature and electric field.
