MOS structure with as-deposited ALD Al2O3/4H-SiC heterostructure with high electrical performance: Investigation of the interfacial region

Abstract

The reliability issues in silicon carbide (SiC)-based devices with gate dielectric formed through heat oxidation are significant factors limiting their application in power devices. Aluminum oxide (Al2O3) was chosen as a high-k material to form the gate oxide layer on top of a SiC substrate. Atomic layer deposition (ALD) was used to fabricate an Al2O3/4H-SiC heterostructure, and the quality of the ALD Al2O3 layer was examined by XPS and electrical experiments. The XPS analysis suggests that the created heterojunction is a type-I heterojunction with ΔEC = 1.89 eV and ΔEV = 1.83 eV. Metal-insulated semiconductor structures with upper and lower Al electrodes were prepared for investigating leakage current and breakdown voltage characteristics. The leakage current density and breakdown electric field of an MOS capacitor structure with an Al2O3/4H-SiC heterojunction are ∼10−10 A/cm2 and 9.3 MV/cm, respectively. The interfacial defect density (Dit) near the conduction band of the MOS capacitive structure with the SiC substrate is 1.44 × 1012 eV−1 cm−2, while the interface charge (Neff) of the oxide layer of this sample can also be controlled at a level of 1011 cm−2. The Al2O3/SiC structure fabricated in this work exhibits superior electrical performance compared to the heterostructure based on the Si substrate and other relevant heterostructures documented in previous studies.