CORRELATION BETWEEN STRUCTURE AND OPTOELECTRONIC PROPERTIES OF UNDOPED MICROCRYSTALLINE SILICON

The correlation between crystallinity and optoelectronic properties of undoped microcrystalline silicon is investigated. The use of the cons tant photocurrent method for measurement of microcrystalline silicon i s discussed. This method measures the true absorption coefficient only if the crystallinity is a major fraction of a sample. If the crystall ine volume fraction is less, it underestimates the absorption coeffici ent at smaller photon energies. At these energies, carriers are mainly photogenerated in the crystalline phase. Carriers generated in isolat ed grains contribute less to the photocurrent than carriers generated in grains which are embedded in percolation paths. The shape of consta nt photocurrent method spectra of microcrystalline silicon with a poor crystallinity differs from spectra of material with better crystallin ity. (C) 1998 Elsevier Science B.V. All rights reserved.