Like silicon, all four elements come from the fourth main group of the periodic table. This makes the alloy compatible with the chip industry's standard process, the CMOS process. "By combining these four elements, we have achieved a long-held goal: the ultimate semiconductor based on the fourth main group," explains Dr. Dan Buca from Forschungszentrum Jülich.
With the new CSiGeSn alloy, properties can be fine-tuned to make components possible that would not be feasible with pure silicon, for example for optical components or in quantum circuits. The structures can be created directly on the chip during production. Chemistry sets clear limits: Only elements that belong to the same main group as silicon fit seamlessly into the crystal lattice on the wafer. Elements from other groups disrupt the structure.
Researchers led by Dan Buca had previously succeeded in combining silicon, germanium and tin to develop transistors, photodetectors, lasers and LEDs - or thermoelectric materials. The addition of carbon now expands the possibilities of specifically adjusting the band gap - which is crucial for electronic and photonic behavior.
The production of the new compound was long considered almost impossible. Carbon is tiny, tin is large and their binding forces are very different. Only by precisely adjusting the manufacturing processes was it possible to unite these opposites - using an industrial CVD system.