AlGaN/GaN heterostructure field-effect transistors with multi-MgxNy/GaN buffer and Photo-CVD SiO2 gate dielectric

We report the fabrication of AlGaN/GaN metal–oxide–semiconductor heterostructure field-effect transistors (MOS-HFETs) with multi-MgxNy/GaN as an epitaxial buffer and using SiO2 dielectric by photochemical vapor deposition (Photo-CVD) simultaneously for surface passivation and as gate insulator. High quality SiO2 dielectric was successfully deposited onto AlGaN by Photo-CVD compared with the traditional plasma enhanced chemical vapor deposition (PE-CVD). Compared to conventional AlGaN/GaN HFET, the MOS-HFET with Photo-CVD SiO2 exhibits lower leakage current, higher breakdown voltage and channel current. It was also observed that our MOS-HFETs presented pure 1/f noise with smaller trapping effects and improved immunity to the RF current collapse.

► The uniform SiO2 dielectric layer on the surface of the AlGaN by using Photo-CVD. ► Photo-CVD SiO2 is an effective gate dielectric for large voltage operation. ► Buffer leakage can be reduced by using multi-MgxNy/GaN buffer. ► MOS-HFETs with multi-MgxNy/GaN buffer have better noise performances.