Interface carbon defects at 4H-SiC(0001)/SiO2 interfaces studied by electron-spin-resonance spectroscopy

We study an electron-spin-resonance (ESR) signal of carbon dangling-bond defects at 4H-SiC(0001)/SiO2 interfaces, which we call an “interface carbon defect.” The ESR signal is close to a c-axial type of the PbC centers (interfacial carbon dangling bonds) that have originally been found in porous-SiC/SiO2 interfaces. The interface carbon defects were always formed with an areal density of 3–4 × 1012 cm−2 after the standard dry oxidation of 4H-SiC(0001) surfaces. They act as electron traps and decrease the amount of free electrons in the channel region, consequently reducing the field-effect mobility of Si-face 4H-SiC MOSFETs. They were eliminated by optimum post-oxidation anneals (POAs) in either NO or POCl3 environment. Furthermore, POCl3 POAs at 1000 °C introduced a high density (1.7 × 1012 cm−2) of phosphorus donors into the channel region, increasing the free-carrier density as compared with the case of NO POAs.