Carola Schwiertz

We investigate the dielectric properties of Praseodymium based oxides and silicates by preparing MIS structures consisting of a metal layer (M), PrO_X (praseodymium oxide) as a high-k insulating layer (I), and silicon (Si) or silicon carbide (SiC) as semiconductor substrates (S).The use of a buffer layer between PrO_X and SiC is necessary as we found destructive interactions like silicate and graphite formation between these materials. Based on a higher permittivity value than SiO₂ and a good lattice matching in conjunction with nearly the same thermal expansion coefficient to SiC, we focus on aluminum oxynitride (AlON) as a suitable buffer layer for this high-k/wide-bandgap system. We report on results achieved by Synchrotron Radiation Photoemission Spectroscopy (SRPES) and by electrical measurements.In our spectroscopic investigations we found a stable AlON/3C-SiC interface as well as no elemental carbon and silicate contributions in the core levels after thin PrO_X deposition and annealing up to 900°C.In electrical characterizations of PrO_X/AlON stacks on silicon we already found a strong improvement in the leakage current down to values of 10^-7 A/cm² at an CET of 4nm. We observed an interface state density in the range of 5x10¹¹-1x10¹²/eVcm² and 1-5x10¹²/eVcm² on Si and SiC, respectively.