We combine high-k dielectrics with wide band gap semiconductors for new possibilities for high frequency and high power applications. We investigate the dielectric properties of Praseodymium based oxides and silicates by preparing MIS structures consisting of metal layer (M), PrOx (praseodymium oxide) as a high-k insulating layer (I), and silicon (Si) or silicon carbide (SiC) as semiconductor substrates (S). Our approach consists both, electrical measurements and spectroscopic characterization to analyze properties of the various interfaces within the stacks.
For the electrical measurements we produce PrOx layers in the thickness range of 10nm to 240nm. We use capacitance-voltage analysis and determine permittivity values of 8 to 20 depending on physical thickness resulting in an equivalent oxide thickness (EOT) down to 5nm. These data are consistent with the formation of a Pr-silicate between Si and PrOx.
In order to prevent interface reactions and to improve the band alignment an interfacial layer is introduced into the stack between the semiconductor and the high-k material. We find aluminum oxynitride (AlON) as a suitable layer which reduces the interface state density to a mean value of 5E11cm2/Vs and the leakage current (1V above flat band) below 1E-5A/cm2.