The chemistry of silane decomposition and possible heterogeneous reactions of admolecules responsible for a-Si: H growth are discussed on the basis of the diagnostic of the silane discharge. Along with the plasma diagnostic, wide optical gap (∼2 eV) and photoconductive (ηµτ≃10-4 cm2V-1) a-SixN1-x: H has been prepared from the glow discharge of a SiH4+NH3 gas mixture. Result of scanning electron microscopy for microcrystalline-like silicon has exhibited the presence of a columnar structure in the film and the structural model consistent with X-ray and IR measurements is proposed. As for electronic characterization of a-Si: H, the acoustic emission due to the nonradiative recombination of photocarriers in the i-layer of the pin junction has, for the first time, been observed and significant correlation between the acoustic signal intensity and the gap states of the i-layer has been demonstrated.