Electroabsorption Spectra of Hydrogenated Amorphous and Microcrystalline Silicon

We report on electroabsorption spectra for plasma deposited thin films of hydrogenated silicon ranging from amorphous (a-Si:H) to microcrystalline (..mu..c-Si:H) structures. The EA spectrum of a-Si:H deposited from silane with low hydrogen dilution were consistent with previous works; material prepared with high hydrogen dilution showed a 0.07 eV blue shift of the spectrum and somewhat strongerelectroabsorption. ..mu..c-Si:H specimens have a sharp peak at 1.19 eV; the spectrum is blue shifted by 0.03 eV and is significantly stronger than electroabsorption reported in single crystal silicon. Spectral features which have no correspondence to single crystal silicon were also observed in ..mu..c-Si:H. Specimens deposited using 'cyclic' deposition and chemical annealing hadelectroabsorption spectra with both the 1.19 eV, crystalline feature and a band peaking at 2.02 eV which we attribute to strongly hydrogenated a-Si:H. We discuss applications of electroabsorption to determining the crystal fraction of microcrystalline material and to determining grain size distributions.