Terahertz multispectral imaging of epitaxially grown semiconductors' lattice defects

Epitaxially grown SiGe and Ge layers on Si <100> substrate have been analyzed by terahertz multispectral reconstructive 3D imaging technique. In particular, 3D images of both samples were generated via a non-contact and non-destructive route and were analyzed by utilizing the terahertz reconstructive imaging algorithm. It was found that the algorithm of “gridding with inverse distance to power equations” adopted herein for reconstructive imaging is capable of reproducing the results accurately as indicated by a good match with the TEM images of the same samples. Both the 3D and 2D images were analyzed by graphical means to determine the respective layers' thicknesses. The results were compared with the TEM images. Both the terahertz and TEM results were found to be in good agreement. Further, the imaging technique was also able to detect and quantify the size of small features of <1 nm present in the SiGe epi layer. In addition, lattice stacking fault and dislocations were also visualized and identified.