Nanometer-scale investigation of metal-SiC interfaces using ballistic electron emission microscopy

We report ballistic-electron emission microscopy (BEEM) investigation of Pd, Pt Schottky contacts on 6H-, 4H-SiC, and Pd/15R-SiC. Measured Schottky barrier heights of 6H- and 4H-SiC samples appear spatially uniform up to the fitting error due to noise (0.03-0.04 eV and 0.1-0.2 eV for 6H- and 4H-SiC, respectively). In 4H-SiC, we observed an additional conduction band minimum (CBM) similar to 0.14 eV above the lowest CBM, which provide direct experimental verification of band theoretical calculation results. Additionally, we sometimes observed enhancement in ballistic transmittance over regions intentionally stressed by hot electron injection using BEEM. We also report recent results on Pd/15R-SiC sample indicating a higher CBM similar to 0.5 eV above the lowest CBM. In Pd/15R-SiC, interesting large variations in BEEM spectra at different locations were observed, possibly suggesting an inhomogeneous metal/semiconductor interface.