Fabrication and characterization of the normally-off N-channel lateral 4H-SiC metal-oxide-semiconductor field-effect transistors

In this paper, the normally-off N-channel lateral 4H-SiC metal-oxide-semiconductor field-effect transistors (MOSFFETs) have been fabricated and characterized. A sandwich-(nitridation-oxidation-nitridation) type process was used to grow the gate dielectric film to obtain high channel mobility. The interface properties of 4H-SiC/SiO₂ were examined by the measurement of HF I-V, G-V, and C-V over a range of frequencies. The ideal C-V curve with little hysteresis and the frequency dispersion were observed. As a result, the interface state density near the conduction band edge of 4H-SiC was reduced to 2×10¹¹ eV^-1·cm^-2, the breakdown field of the grown oxides was about 9.8 MV/cm, the median peak field-effect mobility is about 32.5 cm²·V^-1·s^-1, and the maximum peak field-effect mobility of 38 cm²· V^-1· s^-1 was achieved in fabricated lateral 4H-SiC MOSFFETs.