Comparison of near-interface traps in Al$_2$O$_3$/4H-SiC and   Al$_2$O$_3$/SiO$_2$/4H-SiC structures
  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 0.3 eV 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 to 0.6 eV below Ec. The results indicate the possibility for SiC-based MOSFETs with Al2O3 as the gate dielectric layer in future high performance devices. 
Marc Avice, Ulrike Grossner, Ioana Pintilie, Bengt G. Svensson, Ola   Nilsen and Helmer Fjellvag