Epitaxial growth of ge films onto caf 2/si structures

Heteroepitaxial Ge(insulator/Si structures have been prepared by vacuum evaporation of CaF₂and Ge onto heated (111) and (100) oriented Si substrates. CaF₂films with high crystalline perfection and smooth surface were formed on (111) and (lOO)Si at substrate temperatures of 800°C and 600°C, respectively. Ge films were deposited onto the CaF₂/Si structures at 400°C to 600°C. Higher Ge deposition temperature resulted in increased Ge surface roughness but improved Ge crystalline quality. Both the crystalline quality and the electrical properties of the Ge films on CaF₂/Si(100) structures were superior to those of the Ge films on CaF₂/Si(111) structures.