Trapping of majority carriers in SiO₂/4H-SiC structures

We compared SiO 2 /SiC interface characteristics for three different oxidation processes (dry-oxygen, water-containing oxygen and water-containing nitrogen atmospheres). Metal-oxide-semiconductor (MOS) structures were fabricated on 8° off-axis 4H-SiC(0001) n- and p-type epitaxial wafers. Electrical characteristics were obtained by I – V measurements, high-frequency capacitance–voltage ( C – V ) and ac conductance ( G – V and G –ω) methods. The samples were also characterized by x-ray photoelectron spectroscopy. Results evidence a remarkable difference between n- and p-type doped samples. The p-type samples showed effective oxide charge density up to three orders of magnitude higher than n-type. This fact was explained by the capturing of majority carriers in near interface oxide traps.