CORRELATION BETWEEN STRUCTURE AND OPTOELECTRONIC PROPERTIES OF UNDOPED MICROCRYSTALLINE SILICON

Undoped microcrystalline silicon with various crystallinities was depo sited by ii-glow discharge. We investigate the correlation between cry stallinity and optoelectronic properties, The use of a constant photoc urrent method for characterization of undoped microcrystalline silicon is discussed. In the case of high crystallinity this method measures the true absorption coefficient but with decreasing crystallinity, the constant photocurrent method underestimates the absorption coefficien t at low photon energies, At these energies, carriers are mainly photo generated in the crystalline phase. Carriers generated in isolated gr ains give a smaller contribution to the photocurrent than tamers gener ated in grains forming percolation piths, This results in a strongly d ecreased absorption coefficient measured by the constant photocurrent method at photon energies of about 1.7 eV and below, Therefore, stable microcrystalline silicon with a high crystallinity can be easily dist inguished from an unstable material with poor crystallinity.