Large band gap bowing of MBE-grown Ge_(1-x)C_x/Si(001) layers

摘要

A GeC epilayer is one of the candidates for the light emitting devices, which can be integrated on Si(001) substrate. The Ge_(1-x)C_x epilayer with a substitutional C content of 0.04 ≤ x ≤ 0.11 is expected to have a direct-transition band structure. However, there is no crystallographically stable GeC alloy in the phase diagram, and extremely low solubility of C atoms in bulk Ge (10~8 atom/cm~3 in equilibrium) hinders from realizing high C-content and good-crystalline GeC epilayers. There have been several reports on GeC epitaxial growth by molecular beam epitaxy (MBE) or ultra-high vacuum chemical vapor deposition (UHV-CVD). However, the optical properties and band structure of GeC epilayers have scarcely investigated. In this work, the band gap energy Eg of GeC epilayer is evaluated by Fourier transformation infrared spectroscopy (FT-IR).