Fabrication of an atomically smooth Ge(111) surface by Au-induced crystallization at 170 °C

Crystalline Ge layer fabricated via layer-exchange metal-induced crystallization is a promising candidate as a seed layer for the epitaxial growth of III-V semiconductor thin films for multijunction solar cells. However, small crystalline islands that grow on top of the crystalline Ge layer are a problem, which roughens the surface and hinders subsequent epitaxial growth. Considering the effect of heating rate on the Au-induced crystallization behavior of Ge, it is found that the temperature required for the island growth in the top Ge layer was higher than that for the bottom layer. By carefully choosing the annealing conditions, the growth of the top Ge layer can be avoided resulting in an atomically smooth Ge(111) surface.