The Ge-C local mode in epitaxial GeC and Ge-rich GeSiC alloys

The Raman signature of the local Ge-C mode for substitutional C is identifi ed as a narrow line (8 cm(-1) full width at half maximum) near 530 cm(-1) i n alloy films of Ge1-yCy (0 less than or equal to y less than or equal to 0 .07) grown on Ge (100) substrates by low-temperature (200 degrees C) molecu lar beam epitaxy. The intensity of the Ge-C line relative to the c-Ge line suggests that only a small fraction of the nominal C is in substitutional s ites. In ternary alloys of Ge1-x-ySixCy with x=0.1 and 0.2 and y=0.03, the Ge-C mode disappears, suggesting a strong bias towards C bonding with Si as opposed to Ge. In Ge1-xSnx films the Ge-Sn mode is seen at 263 cm(-1). (C) 1998 American Institute of Physics. [S0003-6951(98)00231-9].