Si/Si1-x-yGexCy/Si heterojunction bipolar transistors

In this letter, we report the first Si/Si1-x-yGexCy/Si n-p-n heterojunction bipolar transistors and the first electrical bandgap measurements of strained Si1-x-yGexCy on Si (100) substrates, The carbon compositions were measured by the shift between the Si1-x-yGexCy and Si1-xGex 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 Si1-xGex at a faster rate than it increases the bandgap (compared to reducing x in Si1-xGex), so that a Si1-x-yGexCy film will have less strain than a Si1-xGex film with the same bandgap.