In this work, we report a study of the optical properties measured through spectral transmission and spectroscopic ellipsometry in Ge:H and GeYSi1 − 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, EU, and defect absorption, αD, have been obtained in Ge:H films for R=50 with EU=0.040 eV and αD=2×103 cm−1 (hν≈1.04 eV), and in GeYSi1 − Y:H films for R=75 with EU=0.030 eV and αD=5×102 cm−1 (hν≈1.04 eV).