Effects of carbon content and plasma power on room temperature photoluminescence characteristics of hydrogenated amorphous silicon carbide thin films deposited by PECVD

The room temperature photoluminescence characteristics of a-SiCx:H thin films, deposited by plasma enhanced chemical vapor deposition technique with various carbon contents (x), at lower (30 mW/cm2) (LP) and higher (90 mW/cm2) (HP) power densities, were analyzed. The carbon content of the a-SiCx:H thin films was determined by X-ray photoelectron spectroscopy. The peak energies and the full width half maxima of the PL spectra were compared with the optical energies, determined by ultraviolet-visible transmittance measurements and a linearly correlated increase was observed as a function of x. PL peak energies shifted from 1.99 eV to 2.60 eV for LP and from 1.89 to 2.91 eV for HP films. The PL mechanisms were investigated in the frame of the static disorder model and the stokes shift model. Our analyses indicated that for LP films the stokes shift model and for HP films the static disorder model are the dominant mechanisms of PL; moreover it was determined that both of these independent models have contributions to PL mechanism. Additionally, PL spectra were analyzed by the joint density of tail states (JDOS) PL model. The increase in the PL peak energies and spectrum widths by the increase in the plasma power and carbon content considerably fitted to JDOS PL model, which could exclusively represent the PL mechanism by itself.