AlGaN/GaN MIS-HEMT with PECVD SiN x , SiON, SiO 2 as gate dielectric and passivation layer

Abstract

Three different insulator layers SiN x , SiON, and SiO 2 were used as a gate dielectric and passivation layer in AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMT). The SiN x , SiON, and SiO 2 were deposited by a plasma-enhanced chemical vapor deposition (PECVD) system. Great differences in the gate leakage current, breakdown voltage, interface traps, and current collapse were observed. The SiON MIS-HEMT exhibited the highest breakdown voltage and I on /I off ratio. The SiN x MIS-HEMT performed well in current collapse but exhibited the highest gate leakage current density. The SiO 2 MIS-HEMT possessed the lowest gate leakage current density but suffered from the early breakdown of the metal–insulator–semiconductor (MIS) diode. As for interface traps, the SiN x MIS-HEMT has the largest shallow trap density and the lowest deep trap density. The SiO 2 MIS-HEMT has the largest deep trap density. The factors causing current collapse were confirmed by Photoluminescence (PL) spectra. Based on the direct current (DC) characteristics, SiN x and SiON both have advantages and disadvantages.