Characterization of Al 2 O 3 /GaN/AlGaN/GaN metal—insulator—semiconductor high electron mobility transistors with different gate recess depths

In this paper, in order to solve the interface-trap issue and enhance the transconductance induced by high- k dielectric in metal—insulator—semiconductor (MIS) high electron mobility transistors (HEMTs), we demonstrate better performances of recessed-gate Al 2 O 3 MIS-HEMTs which are fabricated by Fluorine-based Si 3 N 4 etching and chlorine-based AlGaN etching with three etching times (15 s, 17 s and 19 s). The gate leakage current of MIS-HEMT is about three orders of magnitude lower than that of AlGaN/GaN HEMT. Through the recessed-gate etching, the transconductance increases effectively. When the recessed-gate depth is 1.02 nm, the best interface performance with τ it = (0.20−1.59) μs and D it = (0.55−1.08) × 10 12 cm −2 · eV −1 can be obtained. After chlorine-based etching, the interface trap density reduces considerably without generating any new type of trap. The accumulated chlorine ions and the N vacancies in the AlGaN surface caused by the plasma etching can degrade the breakdown and the high frequency performances of devices. By comparing the characteristics of recessed-gate MIS-HEMTs with different etching times, it is found that a low power chlorine-based plasma etching for a short time (15 s in this paper) can enhance the performances of MIS-HEMTs effectively.