Ge integration on Si via rare earth oxide buffers: From MBE to CVD (Invited Paper)

Single crystalline rare earth oxide heterostructures are flexible buffer systems to achieve the monolithic integration of Ge thin film structures on Si. The development of engineered oxide systems suitable for mass-production compatible CVD processes is hereby of special importance. In this paper, the interaction of Ge with PrO2(1 1 1)/Si(1 1 1) heterostructures is studied in detail to achieve this goal. MBE based in situ growth studies unveil the chemical reduction of the PrO2 buffer during the initial Ge deposition, the occurrence of a Volmer Weber growth mode of Ge on the resulting Pr2O3 heterostructure and the final formation of single crystalline, atomically smooth and c(2 × 8) reconstructed Ge(1 1 1) film structures. Comparative CVD Ge heteroepitaxy studies on MBE grown PrO2(1 1 1)/Si(1 1 1) and Pr2O3(1 1 1)/Si(1 1 1) buffer systems indicate that the highly reactive lattice oxygen of PrO2 plays an active role to avoid during initial exposure to the reducing ambient of the GeH4 precursor chemistry the decomposition of the oxide buffer system.