The influence of boron and phosphorous doping and the effect of structural changes on hydrogen bonding in a-Si:H and µc-Si are investigated using Raman spectroscopy. Information on H bonding is obtained from Si-H stretching local vibrational modes (LVM's). In n-type and undoped a-Si:H the LVM's of isolated Si-H near 2000 cm−1 and clustered Si-H around 2100 cm−1 can be clearly distinguished. In heavily B doped a-Si:H, however, the LVM at 2100 cm−1 disappears. A structural change from a-Si:H to µc-Si gives rise to an additional mode centered at 1911 cm−1. Similar LVM's are observed in poly-Si containing platelets.