Optical absorption and photoluminescence properties ofa−Si1−xNx:Hfilms deposited by plasma-enhanced CVD

Abstract

Optical absorption and photoluminescence (PL) measurements were performed on a series of hydrogenated silicon-nitrogen thin films deposited by plasma enhanced chemical vapor deposition covering a wide compositional range with the aim to find how absorption and emission processes are correlated. Our analysis indicates that the observed broadening of the PL spectra is linked with the existence of band tail states due to topological disorder, as confirmed by the spectral dependence of the PL decay. Moreover, nitrogen alloying reduces the temperature quenching of luminescence and increases the radiative recombination rate. Such phenomena are ascribed to the formation of wide tails in the density of states of N-rich samples and, in turn, to a lower carrier diffusion.