Structure, paramagnetic defects and light-emission of carbon-rich a-SiC:H films

Abstract

The effect of vacuum annealing on local structure reconstruction, evolution of photoluminescence (PL) and paramagnetic defects in carbon-rich a-Si1−xCx:H films (x=0.7) was studied. Strong enhancement of visible (white-green) PL was observed after annealing in the temperature range of 400–500 °C. Such enhancement was correlated with increasing of the concentration of carbon-hydrogen bonds in Si:CHn accompanied with increase in the fluctuation of the interatomic potential. Complete disappearance of PL, “graphitization” of the carbon precipitates, and a strong increase in the concentration of the paramagnetic states were observed after annealing at 650 °C and above. The enhancement and the degradation of PL after different-temperature treatments are explained by the following competing effects: (1) enhancement of the radiative recombination due to passivation of paramagnetic defects with hydrogen and increase of localization of photoexcited electron-hole pairs due to formation of new Si:CH and (2) enhancement of the nonradiative recombination through the paramagnetic states due to increase in their concentration caused by graphitization of carbon precipitates after high- temperature treatment.