Si/Si/sub 1-x-y/GexCy/Si heterojunction bipolar transistors

We report the first Si/Si/sub 1-x-y/Ge/sub x/C/sub y//Si n-p-n heterojunction bipolar transistors and the first electrical bandgap measurements of strained Si/sub 1-x-y/Ge/sub x/C/sub y/ on Si (100) substrates. The carbon compositions were measured by the shift between the Si/sub 1-x-y/Ge/sub x/C/sub y/ and Si/sub 1-x/Ge/sub x/ X-ray diffraction peaks. The temperature dependence of the HBT collector current demonstrates that carbon causes a shift in bandgap of +26 meV/%C for germanium fractions of x=0.2 and x=0.25. These results show that carbon reduces the strain in Si/sub 1-x/Ge/sub x/ at a faster rate than it increases the bandgap (compared to reducing x in Si/sub 1-x/Ge/sub x/), so that a Si/sub 1-x-y/Ge/sub x/C/sub y/ film will have less strain than a Si/sub 1-x/Ge/sub x/ film with the same bandgap.