Comparison of near-interface traps in Al2O3∕4H-SiC and Al2O3∕SiO2∕4H-SiC structures

Abstract

Aluminum oxide (Al2O3) has been grown by atomic layer deposition on n-type 4H-SiC with and without a thin silicon dioxide (SiO2) intermediate layer. By means of capacitance-voltage and thermal dielectric relaxation current measurements, the interface properties have been investigated. Whereas for the samples with an interfacial SiO2 layer the highest near-interface trap density is found at 0.3eV below the conduction band edge Ec, the samples with only the Al2O3 dielectric exhibit a nearly trap-free region close to Ec. For the Al2O3∕SiC interface, the highest trap density appears between 0.4 and 0.6eV below Ec. The results indicate the possibility for SiC-based metal-oxide-semiconductor field-effect transistors with Al2O3 as the gate dielectric layer in future high performance devices.