Nanometer-Scale Investigation of Schottky Contacts and Conduction Band Structure on 4H-, 6H-, and 15R-SiC using Ballistic Electron Emission Microscopy

H.-J. Im, B. Kaczer, and J. P. Pelz
Department of Physics, The Ohio State University, Columbus, Ohio 43210
W. J. Choyke
Department of Physics, University of Pittsburgh, Pittsburgh, Pennsylvania 15260

We have performed ballistic-electron emission microscopy (BEEM) of Pd, Pt Schottky contacts on 6H-, 4H-SiC and Pd/15R-SiC. Measured Schottky barrier heights (SBH's) appear spatially uniform up to the fitting error due to noise (~0.03 and ~0.1 eV for 6H- and 4H-SiC, respectively). In 4H-SiC, we observed an additional conduction band minimum (CBM) ~0.14 eV above the lowest CBM, which is in good agreement with our band theoretical calculation. Preliminary results on Pd/15R-SiC indicate a higher CBM ~0.5 eV above the lowest CBM, and possibly another higher CBM ~0.3 eV above the lowest CBM. Also, in Pd/15R-SiC, large variations in BEEM spectra at different locations were observed, suggesting an inhomogeneous interface. Additionally, we sometimes observed enhancement in ballistic transmittance over regions intentionally stressed by hot electron injection.