Epitaxial growth of high-quality Ge layers on Si with Ge2H6 under UHV-CVD conditions

Epitaxial growth of Ge films on Si(100) substrates has been studied under ultra-high vacuum chemical vapor deposition (CVD) conditions by using digermane (Ge2H6) as the precursor. It was found out that high quality layers with thicknesses beyond 500 nm could be produced at complementary metal–oxide–semiconductor compatible conditions, demonstrating low defect density, sharp and narrow x-ray diffraction peaks, as well as room temperature photoluminescence around 1550 nm. The surface roughness values are comparable to prior reduced pressure CVD results at similar growth temperatures. By employing higher growth temperatures, growth rates are significantly enhanced, resulting in much thicker layers beyond 2000 nm. Smoother sample surface could also be obtained, yielding a state-of-the-art surface root-mean-square roughness value of 0.34 nm for the as-grown sample. At the same time, after being annealed at 750 °C for 20 min, the full width at half maximum (FWHM) of x-ray diffraction 004 rocking curve spectrum of the Ge layer is as low as 88 arcseconds, which stands the best among all Ge/Si samples. The current work has provided important reference for Ge/Si growth with Ge2H6 in low pressure regime and solidified material grounding for Ge-based optoelectronics and Si photonics.