Metal-induced layer exchange of group IV materials

Layer exchange (LE) is an interesting phenomenon in which metal and semiconductor layers exchange during heat treatment. A great deal of effort has been put into research on the mechanism and applications of LE, which has allowed various group IV materials (Si, SiGe, Ge, GeSn and C) to form on arbitrary substrates using appropriate metal catalysts. Depending on the LE material combination and growth conditions, the resulting semiconductor layer exhibits various features: low-temperature crystallization (80 degrees C-500 degrees C), grain size control (nm to mm orders), crystal orientation control to (100) or (111) and high impurity doping (>10(20)cm(-3)). These features are useful for improving the performance, productivity and versatility of various devices, such as solar cells, transistors, thermoelectric generators and rechargeable batteries. We briefly review the findings and achievements from over 20 years of LE studies, including recent progress on device applications.