Ballistic electron emission microscopy study of Schottky contacts on 6H- and 4H-SiC

Abstract

We have performed ballistic-electron emission microscopy (BEEM) on (Pd,Pt)/(6H,4H)-SiC(0001) Schottky contacts. Schottky barrier heights (SBHs) determined from the BEEM data using the Bell–Kaiser model are 1.27 eV/1.34 eV (Pd/Pt) for 6H- and 1.54 eV/1.58 eV for 4H-SiC. Our measurements also give the first direct evidence of a second conduction band minimum (CBM) on 4H-SiC about 0.14 eV above the overall CBM. Spatial inhomogeneity of SBHs were examined and shown to be no larger than the fitting error due to the system noise. Additionally, enhanced ballistic transmittance was observed over a region intentionally stressed by injecting high kinetic energy (10 eV above EF) hot electrons using BEEM in the Pt/4H-SiC sample.