Schottky diodes on Si1-x-yGexCy alloys: Effect of the C-incorporation

S1-x-yGexCy films have been grown by using a rapid thermal chemical deposition reactor. The growth temperatures were 650 degrees C and 550 degrees C and lead to Ge-contents of about 16% and 10%, respectively. The epilayers were characterized by infrared spectroscopy and Raman spectroscopy, The C-fraction varied from 0 to 1.25%, The shifts of Raman frequencies with increasing C-content cannot be explained in terms of change in strain, Electrical characterizations of tungsten contacts to n- and p-type films were achieved through current-voltage measurements. The Schottky barrier on n-type does not depend on the composition, This result indicates that the Fermi level at the interface with W is pinned relative to the conduction band. The Schottky barrier on p-type increased with the C-fraction, The increased magnitude seems to be too large to be explained in terms of variation of the band-gap-energy. The barrier height, for a given C-fraction, is larger for the films prepared at 55O degrees C. This result can be ascribed to the lower Ge-incorporation at low temperature. Some samples were annealed at 1000 degrees C. As expected, substitutional C-atoms precipitate to form silicon carbide. This formation of beta-SiC precipitates results in detrimental effects on Schottky diode properties.