High Performance AlGaN/GaN Metal-Insulator-Semiconductor High Electron Mobility Transistors Fabricated Using SiN/SiO_2/SiN Triple-Layer Insulators

摘要

We proposed and fabricated AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs) using SiN/SiO_2/SiN triple-layer insulators. The role of each insulator is as follows: The topmost SiN film mechanically supports the T-shaped gate, the middle SiO_2 film, which is damaged during the dry etching of the topmost SiN film, can be wet-chemically etched, and the bottom SiN film stabilizes the AlGaN surface. Therefore, the proposed MIS-HEMTs are mechanically stable in the sub-50-nm-gate region and free from damage caused by dry etching. We obtained a cutoff frequency f_T of 139 GHz for a 45-nm-gate MIS-HEMT. This f_T is the highest value for AlGaN/GaN HEMTs grown by metal organic chemical vapor deposition. We also estimated the average electron velocity under the gate to be 2.4 x 10~7 cm/s for a 120-nm-gate MIS-HEMT by transit time analysis.