Electronic characterization of in-grown 8H inclusions in 4H-SiC using Ballistic Electron Emission Microscopy (BEEM)

Planar ``8H'' Stacking-fault inclusions (SFIs) formed during epilayer growth on an 8$^{o}$ miscut n-type 4H-SiC substrate were characterized using nm-resolution BEEM and first-principles electronic structure calculations. Enhanced BEEM current and a $\sim $0.39 eV lower local Schottky Barrier were observed along lines where these inclined SFIs intersect a thin Pt film, indicating that 8H SFIs are electron quantum wells (QWs), as observed for two types of cubic SFIs in 4H-SiC [1,2]. The measured $\sim $0.39 eV QW depth is close to our calculated value of $\sim $0.43 eV. We also observed the BEEM current amplitude and threshold voltage to be quite asymmetric with respect to the intersection lines of the SFIs with the Pt film. We will discuss on-going modeling to see if these asymmetries can be explained respectively by electron reflection from the inclined subsurface SFIs, and by the difference in spontaneous polarization between 8H- and 4H-SiC. Work supported by ONR. [1] Ding \textit{et al}., Phys. Rev. B\textbf{ 69}, 041305(R) (2004). [2] Park \textit{et al}., Appl. Phys. Lett. \textbf{87}, 232103 (2005).