Liquid phase crystallization of Ge over direct Si substrate as a template for GaAs applications

The direct growth of Ge over Si substrates provides a complementary metal-oxide-semiconductor compatible low-cost way that can be used as a template for GaAs based solar cell and other applications. In this work, the previously reported liquid phase crystallization (LPC) process from our group is used to grow crystalline Ge directly over the Si substrate. No buffer layer is used to relax the lattice mismatch induced strain. The results show a crystalline growth of Ge that is confirmed from x-ray diffraction measurement. The surface morphology is investigated using scanning electron microscope, showing large grain growth in the range from 2-10 μm. The transmission electron microscope investigations show that the threading dislocation densities extend up to ~250 nm from the Si/Ge interface. After ~250 nm from the Si/Ge interface, the Ge film becomes relaxed and hence, can be used as a template for GaAs based solar cell devices.