Study of Ge_YSi_{1 - Y}:H films deposited by low frequency plasma

In this work, we report a study of the optical properties measured through spectral transmission and spectroscopic ellipsometry in Ge:H and Ge_YSi_{1 - Y}:H (Y ≈ 0.97) films deposited by low frequency (LF) PE CVD with hydrogen (H) dilution. The dilution was varied in the range of R = 20 to 80. It was observed that H-dilution influences in a different way on the interface and bulk optical properties, which also depend on incorporation of silicon. The films with low band tail characterized by its Urbach energy, E_U, and defect absorption, α_D, have been obtained in Ge:H films for R = 50 with E_U = 0.040 eV and α_D = 2 × 10³ cm^{- 1} (hν ≈ 1.04 eV), and in Ge_YSi_{1 - Y}:H films for R=75 with E_U = 0.030 eV and α_D = 5 × 10² cm^{- 1} (hν ≈ 1.04 eV).