Si and Ge were the first semiconductors to be exploited commercially on a large scale and play a key role in microelectronics. Unfortunately, group IV semiconductors do not display a direct band gap, which precludes their use as active layers in LEDs and LASERs devices.

After the success with IV-IV materials, such as GeSi-on-Si, SiC-on-Si and Ge-on-Si, researchers started to explore IV-IV systems capable of displaying direct band gap. In 1980’s it was suggested that a solid solution of Ge and Sn could be a candidate to achieve direct band gap, but the fabrication technology to grow GeSn was not ready. More recently, thin film single crystal growth improved significantly to facilitate the growth of GeSn materials.
The IV-IV semiconductors based on Si technology with direct band gap would allow the production of affordable electronic and photonic integrated circuits in one single chip.

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