EQUILIBRIUM DENSITY OF DEFECTS IN HYDROGENATED AMORPHOUS-SILICON CARBON ALLOYS

In this work, we compare experimental measured density of defects in amorphous silicon-carbon alloys with a theoretical expression obtained by applying a thermodynamic equilibrium defects model to the intrinsic defect concentration in the semiconductor. The samples were deposited under different conditions of hydrogen dilutions and two substrate temperatures. The density of defects was determined by photothermal deflection and photoconductivity spectroscopy. The expression of the equilibrium density of defects is obtained starting from the canonical partition function assuming two independent systems of Si-Si and Si-C dangling bonds. A weak-bond defect formation reaction is assumed in the analysis. Linear approximations of the equilibrium temperature and the valence band exponential decay (Urbach's tail) are used for the numerical calculations. The trend of the experimental data are well represented by the theoretical expression. The model, however, overestimates the density of defects in samples deposited onto substrata maintained at the lower of two temperatures.