A comparison between SiO_2/4H-SiC interface traps on (0001) and (1120) faces

摘要

We present thermally stimulated current (TSC) measurements made on metal-oxide-semiconductor (MOS) structures fabricated on off-axis (0001) or on-axis (1120) face n-type 4H-SiC with wet or dry oxides. The TSC measurements show the interface trap spectra of traps with activation energies in the range from 0.1 to 0.6 eV. Varying the charging and discharging conditions, we are able to distinguish between two types of traps which are both present on (0001) and (1120) face samples. One type is sensitive to the electric field during discharging but is insensitive to the charging temperature, while the other type is insensitive to the electric field during discharging but can not capture electrons at low temperatures. We find that, compared to the (0001) face, the traps at the (1120) face are shifted in energy about 0.1 eV towards higher activation energies. In all cases, for wet or dry oxides made on the (0001) or the (1120) face, the number density of traps is above 7xl0~(12) cm~(-2).