Analysis of slow de-trapping phenomena after a positive gate bias on AlGaN/GaN MIS-HEMTs with in-situ Si3N4/Al2O3 bilayer gate dielectrics

We focus on slow de-trapping phenomena in AlGaN/GaN MIS-HEMTs with a bilayer dielectric (in-situ Si3N4/Al2O3) with two different thicknesses of in-situ Si3N4 (10 nm and 5 nm). By using a "filling pulse" at a positive gate voltage, a trap with activation energy of 0.69-0.7 eV was identified to be responsible for the VTH shift. Based on literature, filling conditions, and the simulated band diagrams, this trap is most probably located at the interface between the dielectrics and AlGaN barrier. A physical model is proposed to explain the VTH shift due to the trapping/de-trapping phenomena based on the occupation dynamics of donor traps at the interface between the in-situ Si3N4/Al2O3 and the AlGaN barrier