Abstract
Hysteresis phenomenon in the capacitance–voltage characteristics and leakage current under reverse-biased Schottky gate were investigated for Al0.25Ga0.75N/GaN/SiC HEMT's with two different gate lengths. These phenomena were attributed to the electron tunneling through the surface, the bulk or/and the metal/AlGaN interface states. Using Capacitance DLTS, we have found that the deep trap responsible of these phenomena has activation energy of 0.74eV. It was an extended defect in the AlGaN/GaN heterostructures. Else, an electron trap (Ea=0.16eV) was detected only in the transistor having the smaller gate length. The possible explanations of its origin will be established in this paper.