HYDROGEN IN AMORPHOUS-SILICON - LOCAL BONDING AND VIBRATIONAL PROPERTIES

This paper discusses the bonding of hydrogen to silicon, alloy and dopant atoms in amorphous silicon based alloys including a-Si:H, a-Si,C:H, a-Si,Ge:H, a-Si,O:H and a-Si,N:H, and in phosphorus and boron doped a-Si:H. Two aspects of hydrogen incorporation are emphasized: (i) local bonding arrangements of hydrogen atoms which also include alloy or dopant atoms as near-neighbors; and (ii) chemical-bonding induced shifts in Si-H bond-stretching frequencies that derive from a combination of the local bonding arrangements of the alloy atoms, and the average chemical composition of the alloy. For the undoped a-Si:H alloys, both monohydride and polyhydride configurations are discussed, whereas for the alloys, and doped a-Si:H, the discussion is restricted to the monohydride arrangements that dominate in the so-called device-grade materials.