Electrical behavior of 4H-SiC metal-oxide-semiconductor structures with Al2O3 as gate dielectric

The electrical properties of Al2O3 as a gate dielectric in metal-oxide-semiconductor structures based on n- and p-type 4H-SiC grown by sublimation method have been investigated and compared to the properties of similar structures utilizing SiO2. The electrically active defects in the structures are studied by capacitance–voltage (C–V) and current–voltage (I–V) methods. The results show that the type as well as spatial and energy distributions of defects in Al2O3∕SiC and SiO2∕SiC samples are different. The structures with Al2O3 on p-type 4H-SiC demonstrate much better electrical characteristics than the p-type 4H-SiC∕SiO2 structures. It is demonstrated that the conduction process in the former is governed by Fowler–Nordheim electron tunneling from the Al gate whereas in the latter the hole tunneling from SiC is the more probable process. This difference combined with the higher defect density in p-type SiC∕SiO2 structures defines the higher leakage currents compared to the structures utilizing Al2O3.