Leakage current, capacitance hysteresis and deep traps in Al0.25Ga0.75N/GaN/SiC high-electron-mobility transistors

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 0.74 eV. It was an extended defect in the AlGaN/GaN heterostructures. Else, an electron trap (Ea=0.16 eV) was detected only in the transistor having the smaller gate length. The possible explanations of its origin will be established in this paper.