Currently, single crystal Germanium (Ge) must be grown via a chemical vapor deposition or molecular beam epitaxy process on a single crystal substrate in order to be compatible with complementary metal oxide semiconductor (CMOS) technology. This standard procedure limits the processing flexibility for it requires both high temperatures (around 700 ̊C ) and a single crystal substrate.
Crystal growth on amorphous substrates at low temperature (around 400 ̊C) allows for the flexible fabrication of Ge electronic and photonic devices. For example, such a process could be used for the back end fabrication of Ge photonic devices where high temperatures are not needed. The essential aspect of the procedure is that the crystal is initially grown laterally (instead of vertically) from a seed layer and is confined between two insulating layers. This confinement ensures the grown material is single crystalline.