Germanium-on-insulator (GeOI) substrates—A novel engineered substrate for future high performance devices

Germanium-on-insulator (GeOI), which combines high mobility of charge carriers with the advantages of an SOI structure, is an attractive integration platform for the future IC technology. Also, due to its low lattice mismatch with GaAs, III-V compounds transistors as well as optoelectronic functions can be integrated on GeOI. In this paper, we review GeOI fabrication methods, and then applications that utilize GeOI wafers. The Smart Cut™ layer transfer technology is found to be the best method to form wafer-level GeOI structures of different diameters and thickness range down to < 50 nm. Thereby, the impact of the donor wafer used for the GeOI formation is also discussed. With Ge epitaxially grown on Si utilized as a donor material for layer transfer, we see no technical obstacles in moving to 300 mm wafer diameter and beyond. However, for higher quality crystal needs, Ge bulk wafers are to be considered as the starting material. Demonstrated functioning sub-micron fully depleted GeOI MOSFETs and its compatibility with Si CMOS full sheet process exhibits its high potential for the 32 nm technology node and beyond. Furthermore, the optoelectronics applications such as high-speed and high efficiency photodetectors are discussed. As epitaxy template of high quality IIIV growth, GeOI opens the path to the integration of high performance III-V opto-electronics to mature Si technology.