Anomaly and defects characterization by I-V and current deep level transient spectroscopy of Al0.25Ga0.75N/GaN/SiC high electron-mobility transistors

In this paper, we report static electric drain-source current-voltage measurements for different gate voltages and at different temperatures, performed on Al0.25Ga0.75N/GaN/SiC high electron-mobility transistors (HEMT). The results show the presence of kink and collapse effects. We have demonstrated that these effects are significant in the temperature range varying from 150 to 400 K with a maximum around 300 K. This parasitic effect was correlated with the presence of deep levels in our transistor. Indeed, we have noticed the presence of two electron traps named A1 and A2, and one hole trap named H1; their respective activation energies, which are determined using current deep level transient spectroscopy (CDLTS), are, respectively, 0.56, 0.82, and 0.75 eV. Traps H1 and A1 are shown to be extended defects in the Al0.25Ga0.75N/GaN heterostructure; they are supposed to be the origin of the kink and collapse effects. However, the punctual defect A2 seems to be located either in the free gate-drain surface, in the metal/AlGaN interface, or in the AlGaN/GaN interface.