Features of hydrogenated amorphous silicon films developed under an unexplored region of parameter space of radio-frequency plasma-enhanced chemical vapor deposition

Searching to improve stability of electronic properties under intense light illumination, hydrogenated amorphous silicon (a-Si:H) films have been fabr icated by radio-frequency plasma-enhanced chemical vapor deposition with he lium dilution of silane. The deposition conditions which correspond to the transition between the alpha regime and the powder regime have not been exp lored properly yet. The resulting materials show many new features: hydroge n bonding mostly monohydride, lower bonded hydrogen content, compact struct ure, higher efficiency-mobility-lifetime product (eta mu tau) and density o f states (DOS) above Fermi level lower than the reported values of the stat e-of-the-art a-Si:H films. The saturation time under light-soaking (AM 1) i s fast (within 20 h) and the saturated value of eta mu tau and the DOS abov e the Fermi level is comparable to that of annealed state standard a-Si:H f ilms. (C) 2000 American Institute of Physics. [S0003-6951(00)00517-9].