Investigation of unusual mobile ion effects in thermally grown SiO2 on 4H-SiC(0001) at high temperatures

Generation and elimination of mobile ions in thermally grown SiO2 on 4H-SiC(0001) were systematically investigated by electrical measurements of MOS capacitors. In contrast to a SiO2/Si system, intrinsic positive mobile ions were found to exist in as-oxidized SiO2/SiC structures, leading to significant instability of SiC-MOS devices. Post-oxidation annealing in Ar ambient mostly eliminates the mobile ions, but they are generated again by subsequent high-temperature hydrogen annealing despite the improved interface quality. The density of the mobile ions was estimated to be several 10(12) cm(-2). Possible physical origins of the mobile ions are discussed on the basis of the experimental findings. (C) 2012 American Institute of Physics. [http:// dx. doi. org/ 10.1063/ 1.4729780]